diff --git a/block.c b/block.c
index 8f17750..64412ee 100644
--- a/block.c
+++ b/block.c
@@ -1900,10 +1900,9 @@
 
 static int bdrv_child_check_perm(BdrvChild *c, BlockReopenQueue *q,
                                  uint64_t perm, uint64_t shared,
-                                 GSList *ignore_children,
-                                 bool *tighten_restrictions, Error **errp);
+                                 GSList *ignore_children, Error **errp);
 static void bdrv_child_abort_perm_update(BdrvChild *c);
-static void bdrv_child_set_perm(BdrvChild *c, uint64_t perm, uint64_t shared);
+static void bdrv_child_set_perm(BdrvChild *c);
 
 typedef struct BlockReopenQueueEntry {
      bool prepared;
@@ -1974,43 +1973,18 @@
  * permissions of all its parents. This involves checking whether all necessary
  * permission changes to child nodes can be performed.
  *
- * Will set *tighten_restrictions to true if and only if new permissions have to
- * be taken or currently shared permissions are to be unshared.  Otherwise,
- * errors are not fatal as long as the caller accepts that the restrictions
- * remain tighter than they need to be.  The caller still has to abort the
- * transaction.
- * @tighten_restrictions cannot be used together with @q: When reopening, we may
- * encounter fatal errors even though no restrictions are to be tightened.  For
- * example, changing a node from RW to RO will fail if the WRITE permission is
- * to be kept.
- *
  * A call to this function must always be followed by a call to bdrv_set_perm()
  * or bdrv_abort_perm_update().
  */
 static int bdrv_check_perm(BlockDriverState *bs, BlockReopenQueue *q,
                            uint64_t cumulative_perms,
                            uint64_t cumulative_shared_perms,
-                           GSList *ignore_children,
-                           bool *tighten_restrictions, Error **errp)
+                           GSList *ignore_children, Error **errp)
 {
     BlockDriver *drv = bs->drv;
     BdrvChild *c;
     int ret;
 
-    assert(!q || !tighten_restrictions);
-
-    if (tighten_restrictions) {
-        uint64_t current_perms, current_shared;
-        uint64_t added_perms, removed_shared_perms;
-
-        bdrv_get_cumulative_perm(bs, &current_perms, &current_shared);
-
-        added_perms = cumulative_perms & ~current_perms;
-        removed_shared_perms = current_shared & ~cumulative_shared_perms;
-
-        *tighten_restrictions = added_perms || removed_shared_perms;
-    }
-
     /* Write permissions never work with read-only images */
     if ((cumulative_perms & (BLK_PERM_WRITE | BLK_PERM_WRITE_UNCHANGED)) &&
         !bdrv_is_writable_after_reopen(bs, q))
@@ -2054,8 +2028,11 @@
     }
 
     if (drv->bdrv_check_perm) {
-        return drv->bdrv_check_perm(bs, cumulative_perms,
-                                    cumulative_shared_perms, errp);
+        ret = drv->bdrv_check_perm(bs, cumulative_perms,
+                                   cumulative_shared_perms, errp);
+        if (ret < 0) {
+            return ret;
+        }
     }
 
     /* Drivers that never have children can omit .bdrv_child_perm() */
@@ -2067,18 +2044,12 @@
     /* Check all children */
     QLIST_FOREACH(c, &bs->children, next) {
         uint64_t cur_perm, cur_shared;
-        bool child_tighten_restr;
 
         bdrv_child_perm(bs, c->bs, c, c->role, q,
                         cumulative_perms, cumulative_shared_perms,
                         &cur_perm, &cur_shared);
         ret = bdrv_child_check_perm(c, q, cur_perm, cur_shared, ignore_children,
-                                    tighten_restrictions ? &child_tighten_restr
-                                                         : NULL,
                                     errp);
-        if (tighten_restrictions) {
-            *tighten_restrictions |= child_tighten_restr;
-        }
         if (ret < 0) {
             return ret;
         }
@@ -2112,9 +2083,9 @@
     }
 }
 
-static void bdrv_set_perm(BlockDriverState *bs, uint64_t cumulative_perms,
-                          uint64_t cumulative_shared_perms)
+static void bdrv_set_perm(BlockDriverState *bs)
 {
+    uint64_t cumulative_perms, cumulative_shared_perms;
     BlockDriver *drv = bs->drv;
     BdrvChild *c;
 
@@ -2122,6 +2093,8 @@
         return;
     }
 
+    bdrv_get_cumulative_perm(bs, &cumulative_perms, &cumulative_shared_perms);
+
     /* Update this node */
     if (drv->bdrv_set_perm) {
         drv->bdrv_set_perm(bs, cumulative_perms, cumulative_shared_perms);
@@ -2135,11 +2108,7 @@
 
     /* Update all children */
     QLIST_FOREACH(c, &bs->children, next) {
-        uint64_t cur_perm, cur_shared;
-        bdrv_child_perm(bs, c->bs, c, c->role, NULL,
-                        cumulative_perms, cumulative_shared_perms,
-                        &cur_perm, &cur_shared);
-        bdrv_child_set_perm(c, cur_perm, cur_shared);
+        bdrv_child_set_perm(c);
     }
 }
 
@@ -2203,22 +2172,18 @@
  * set, the BdrvChild objects in this list are ignored in the calculations;
  * this allows checking permission updates for an existing reference.
  *
- * See bdrv_check_perm() for the semantics of @tighten_restrictions.
- *
  * Needs to be followed by a call to either bdrv_set_perm() or
  * bdrv_abort_perm_update(). */
 static int bdrv_check_update_perm(BlockDriverState *bs, BlockReopenQueue *q,
                                   uint64_t new_used_perm,
                                   uint64_t new_shared_perm,
                                   GSList *ignore_children,
-                                  bool *tighten_restrictions,
                                   Error **errp)
 {
     BdrvChild *c;
     uint64_t cumulative_perms = new_used_perm;
     uint64_t cumulative_shared_perms = new_shared_perm;
 
-    assert(!q || !tighten_restrictions);
 
     /* There is no reason why anyone couldn't tolerate write_unchanged */
     assert(new_shared_perm & BLK_PERM_WRITE_UNCHANGED);
@@ -2232,10 +2197,6 @@
             char *user = bdrv_child_user_desc(c);
             char *perm_names = bdrv_perm_names(new_used_perm & ~c->shared_perm);
 
-            if (tighten_restrictions) {
-                *tighten_restrictions = true;
-            }
-
             error_setg(errp, "Conflicts with use by %s as '%s', which does not "
                              "allow '%s' on %s",
                        user, c->name, perm_names, bdrv_get_node_name(c->bs));
@@ -2248,10 +2209,6 @@
             char *user = bdrv_child_user_desc(c);
             char *perm_names = bdrv_perm_names(c->perm & ~new_shared_perm);
 
-            if (tighten_restrictions) {
-                *tighten_restrictions = true;
-            }
-
             error_setg(errp, "Conflicts with use by %s as '%s', which uses "
                              "'%s' on %s",
                        user, c->name, perm_names, bdrv_get_node_name(c->bs));
@@ -2265,21 +2222,19 @@
     }
 
     return bdrv_check_perm(bs, q, cumulative_perms, cumulative_shared_perms,
-                           ignore_children, tighten_restrictions, errp);
+                           ignore_children, errp);
 }
 
 /* Needs to be followed by a call to either bdrv_child_set_perm() or
  * bdrv_child_abort_perm_update(). */
 static int bdrv_child_check_perm(BdrvChild *c, BlockReopenQueue *q,
                                  uint64_t perm, uint64_t shared,
-                                 GSList *ignore_children,
-                                 bool *tighten_restrictions, Error **errp)
+                                 GSList *ignore_children, Error **errp)
 {
     int ret;
 
     ignore_children = g_slist_prepend(g_slist_copy(ignore_children), c);
-    ret = bdrv_check_update_perm(c->bs, q, perm, shared, ignore_children,
-                                 tighten_restrictions, errp);
+    ret = bdrv_check_update_perm(c->bs, q, perm, shared, ignore_children, errp);
     g_slist_free(ignore_children);
 
     if (ret < 0) {
@@ -2302,18 +2257,11 @@
     return 0;
 }
 
-static void bdrv_child_set_perm(BdrvChild *c, uint64_t perm, uint64_t shared)
+static void bdrv_child_set_perm(BdrvChild *c)
 {
-    uint64_t cumulative_perms, cumulative_shared_perms;
-
     c->has_backup_perm = false;
 
-    c->perm = perm;
-    c->shared_perm = shared;
-
-    bdrv_get_cumulative_perm(c->bs, &cumulative_perms,
-                             &cumulative_shared_perms);
-    bdrv_set_perm(c->bs, cumulative_perms, cumulative_shared_perms);
+    bdrv_set_perm(c->bs);
 }
 
 static void bdrv_child_abort_perm_update(BdrvChild *c)
@@ -2327,18 +2275,33 @@
     bdrv_abort_perm_update(c->bs);
 }
 
+static int bdrv_refresh_perms(BlockDriverState *bs, Error **errp)
+{
+    int ret;
+    uint64_t perm, shared_perm;
+
+    bdrv_get_cumulative_perm(bs, &perm, &shared_perm);
+    ret = bdrv_check_perm(bs, NULL, perm, shared_perm, NULL, errp);
+    if (ret < 0) {
+        bdrv_abort_perm_update(bs);
+        return ret;
+    }
+    bdrv_set_perm(bs);
+
+    return 0;
+}
+
 int bdrv_child_try_set_perm(BdrvChild *c, uint64_t perm, uint64_t shared,
                             Error **errp)
 {
     Error *local_err = NULL;
     int ret;
-    bool tighten_restrictions;
 
-    ret = bdrv_child_check_perm(c, NULL, perm, shared, NULL,
-                                &tighten_restrictions, &local_err);
+    ret = bdrv_child_check_perm(c, NULL, perm, shared, NULL, &local_err);
     if (ret < 0) {
         bdrv_child_abort_perm_update(c);
-        if (tighten_restrictions) {
+        if ((perm & ~c->perm) || (c->shared_perm & ~shared)) {
+            /* tighten permissions */
             error_propagate(errp, local_err);
         } else {
             /*
@@ -2353,7 +2316,7 @@
         return ret;
     }
 
-    bdrv_child_set_perm(c, perm, shared);
+    bdrv_child_set_perm(c);
 
     return 0;
 }
@@ -2623,7 +2586,6 @@
 static void bdrv_replace_child(BdrvChild *child, BlockDriverState *new_bs)
 {
     BlockDriverState *old_bs = child->bs;
-    uint64_t perm, shared_perm;
 
     /* Asserts that child->frozen == false */
     bdrv_replace_child_noperm(child, new_bs);
@@ -2637,27 +2599,16 @@
      * restrictions.
      */
     if (new_bs) {
-        bdrv_get_cumulative_perm(new_bs, &perm, &shared_perm);
-        bdrv_set_perm(new_bs, perm, shared_perm);
+        bdrv_set_perm(new_bs);
     }
 
     if (old_bs) {
-        /* Update permissions for old node. This is guaranteed to succeed
-         * because we're just taking a parent away, so we're loosening
-         * restrictions. */
-        bool tighten_restrictions;
-        int ret;
-
-        bdrv_get_cumulative_perm(old_bs, &perm, &shared_perm);
-        ret = bdrv_check_perm(old_bs, NULL, perm, shared_perm, NULL,
-                              &tighten_restrictions, NULL);
-        assert(tighten_restrictions == false);
-        if (ret < 0) {
-            /* We only tried to loosen restrictions, so errors are not fatal */
-            bdrv_abort_perm_update(old_bs);
-        } else {
-            bdrv_set_perm(old_bs, perm, shared_perm);
-        }
+        /*
+         * Update permissions for old node. We're just taking a parent away, so
+         * we're loosening restrictions. Errors of permission update are not
+         * fatal in this case, ignore them.
+         */
+        bdrv_refresh_perms(old_bs, NULL);
 
         /* When the parent requiring a non-default AioContext is removed, the
          * node moves back to the main AioContext */
@@ -2687,8 +2638,7 @@
     Error *local_err = NULL;
     int ret;
 
-    ret = bdrv_check_update_perm(child_bs, NULL, perm, shared_perm, NULL, NULL,
-                                 errp);
+    ret = bdrv_check_update_perm(child_bs, NULL, perm, shared_perm, NULL, errp);
     if (ret < 0) {
         bdrv_abort_perm_update(child_bs);
         bdrv_unref(child_bs);
@@ -3820,7 +3770,7 @@
     QTAILQ_FOREACH(bs_entry, bs_queue, entry) {
         BDRVReopenState *state = &bs_entry->state;
         ret = bdrv_check_perm(state->bs, bs_queue, state->perm,
-                              state->shared_perm, NULL, NULL, errp);
+                              state->shared_perm, NULL, errp);
         if (ret < 0) {
             goto cleanup_perm;
         }
@@ -3832,7 +3782,7 @@
                             bs_queue, state->perm, state->shared_perm,
                             &nperm, &nshared);
             ret = bdrv_check_update_perm(state->new_backing_bs, NULL,
-                                         nperm, nshared, NULL, NULL, errp);
+                                         nperm, nshared, NULL, errp);
             if (ret < 0) {
                 goto cleanup_perm;
             }
@@ -3863,7 +3813,13 @@
         }
 
         if (ret == 0) {
-            bdrv_set_perm(state->bs, state->perm, state->shared_perm);
+            uint64_t perm, shared;
+
+            bdrv_get_cumulative_perm(state->bs, &perm, &shared);
+            assert(perm == state->perm);
+            assert(shared == state->shared_perm);
+
+            bdrv_set_perm(state->bs);
         } else {
             bdrv_abort_perm_update(state->bs);
             if (state->replace_backing_bs && state->new_backing_bs) {
@@ -4616,7 +4572,7 @@
 
     /* Check whether the required permissions can be granted on @to, ignoring
      * all BdrvChild in @list so that they can't block themselves. */
-    ret = bdrv_check_update_perm(to, NULL, perm, shared, list, NULL, errp);
+    ret = bdrv_check_update_perm(to, NULL, perm, shared, list, errp);
     if (ret < 0) {
         bdrv_abort_perm_update(to);
         goto out;
@@ -4633,8 +4589,7 @@
         bdrv_unref(from);
     }
 
-    bdrv_get_cumulative_perm(to, &perm, &shared);
-    bdrv_set_perm(to, perm, shared);
+    bdrv_set_perm(to);
 
 out:
     g_slist_free(list);
@@ -5781,7 +5736,6 @@
 int coroutine_fn bdrv_co_invalidate_cache(BlockDriverState *bs, Error **errp)
 {
     BdrvChild *child, *parent;
-    uint64_t perm, shared_perm;
     Error *local_err = NULL;
     int ret;
     BdrvDirtyBitmap *bm;
@@ -5813,14 +5767,11 @@
      */
     if (bs->open_flags & BDRV_O_INACTIVE) {
         bs->open_flags &= ~BDRV_O_INACTIVE;
-        bdrv_get_cumulative_perm(bs, &perm, &shared_perm);
-        ret = bdrv_check_perm(bs, NULL, perm, shared_perm, NULL, NULL, errp);
+        ret = bdrv_refresh_perms(bs, errp);
         if (ret < 0) {
-            bdrv_abort_perm_update(bs);
             bs->open_flags |= BDRV_O_INACTIVE;
             return ret;
         }
-        bdrv_set_perm(bs, perm, shared_perm);
 
         if (bs->drv->bdrv_co_invalidate_cache) {
             bs->drv->bdrv_co_invalidate_cache(bs, &local_err);
@@ -5895,8 +5846,6 @@
 static int bdrv_inactivate_recurse(BlockDriverState *bs)
 {
     BdrvChild *child, *parent;
-    bool tighten_restrictions;
-    uint64_t perm, shared_perm;
     int ret;
 
     if (!bs->drv) {
@@ -5930,18 +5879,12 @@
 
     bs->open_flags |= BDRV_O_INACTIVE;
 
-    /* Update permissions, they may differ for inactive nodes */
-    bdrv_get_cumulative_perm(bs, &perm, &shared_perm);
-    ret = bdrv_check_perm(bs, NULL, perm, shared_perm, NULL,
-                          &tighten_restrictions, NULL);
-    assert(tighten_restrictions == false);
-    if (ret < 0) {
-        /* We only tried to loosen restrictions, so errors are not fatal */
-        bdrv_abort_perm_update(bs);
-    } else {
-        bdrv_set_perm(bs, perm, shared_perm);
-    }
-
+    /*
+     * Update permissions, they may differ for inactive nodes.
+     * We only tried to loosen restrictions, so errors are not fatal, ignore
+     * them.
+     */
+    bdrv_refresh_perms(bs, NULL);
 
     /* Recursively inactivate children */
     QLIST_FOREACH(child, &bs->children, next) {
diff --git a/block/file-posix.c b/block/file-posix.c
index 9804681..00cdaaa 100644
--- a/block/file-posix.c
+++ b/block/file-posix.c
@@ -2953,7 +2953,7 @@
 
         assert(bdrv_check_request(req->offset, req->bytes) == 0);
 
-        bdrv_mark_request_serialising(req, bs->bl.request_alignment);
+        bdrv_make_request_serialising(req, bs->bl.request_alignment);
     }
 #endif
 
diff --git a/block/io.c b/block/io.c
index 24205f5..95b1c56 100644
--- a/block/io.c
+++ b/block/io.c
@@ -754,55 +754,65 @@
     return true;
 }
 
-static bool coroutine_fn
-bdrv_wait_serialising_requests_locked(BlockDriverState *bs,
-                                      BdrvTrackedRequest *self)
+/* Called with self->bs->reqs_lock held */
+static BdrvTrackedRequest *
+bdrv_find_conflicting_request(BdrvTrackedRequest *self)
 {
     BdrvTrackedRequest *req;
-    bool retry;
-    bool waited = false;
 
-    do {
-        retry = false;
-        QLIST_FOREACH(req, &bs->tracked_requests, list) {
-            if (req == self || (!req->serialising && !self->serialising)) {
-                continue;
-            }
-            if (tracked_request_overlaps(req, self->overlap_offset,
-                                         self->overlap_bytes))
-            {
-                /* Hitting this means there was a reentrant request, for
-                 * example, a block driver issuing nested requests.  This must
-                 * never happen since it means deadlock.
-                 */
-                assert(qemu_coroutine_self() != req->co);
+    QLIST_FOREACH(req, &self->bs->tracked_requests, list) {
+        if (req == self || (!req->serialising && !self->serialising)) {
+            continue;
+        }
+        if (tracked_request_overlaps(req, self->overlap_offset,
+                                     self->overlap_bytes))
+        {
+            /*
+             * Hitting this means there was a reentrant request, for
+             * example, a block driver issuing nested requests.  This must
+             * never happen since it means deadlock.
+             */
+            assert(qemu_coroutine_self() != req->co);
 
-                /* If the request is already (indirectly) waiting for us, or
-                 * will wait for us as soon as it wakes up, then just go on
-                 * (instead of producing a deadlock in the former case). */
-                if (!req->waiting_for) {
-                    self->waiting_for = req;
-                    qemu_co_queue_wait(&req->wait_queue, &bs->reqs_lock);
-                    self->waiting_for = NULL;
-                    retry = true;
-                    waited = true;
-                    break;
-                }
+            /*
+             * If the request is already (indirectly) waiting for us, or
+             * will wait for us as soon as it wakes up, then just go on
+             * (instead of producing a deadlock in the former case).
+             */
+            if (!req->waiting_for) {
+                return req;
             }
         }
-    } while (retry);
+    }
+
+    return NULL;
+}
+
+/* Called with self->bs->reqs_lock held */
+static bool coroutine_fn
+bdrv_wait_serialising_requests_locked(BdrvTrackedRequest *self)
+{
+    BdrvTrackedRequest *req;
+    bool waited = false;
+
+    while ((req = bdrv_find_conflicting_request(self))) {
+        self->waiting_for = req;
+        qemu_co_queue_wait(&req->wait_queue, &self->bs->reqs_lock);
+        self->waiting_for = NULL;
+        waited = true;
+    }
+
     return waited;
 }
 
-bool bdrv_mark_request_serialising(BdrvTrackedRequest *req, uint64_t align)
+/* Called with req->bs->reqs_lock held */
+static void tracked_request_set_serialising(BdrvTrackedRequest *req,
+                                            uint64_t align)
 {
-    BlockDriverState *bs = req->bs;
     int64_t overlap_offset = req->offset & ~(align - 1);
     uint64_t overlap_bytes = ROUND_UP(req->offset + req->bytes, align)
                                - overlap_offset;
-    bool waited;
 
-    qemu_co_mutex_lock(&bs->reqs_lock);
     if (!req->serialising) {
         qatomic_inc(&req->bs->serialising_in_flight);
         req->serialising = true;
@@ -810,9 +820,6 @@
 
     req->overlap_offset = MIN(req->overlap_offset, overlap_offset);
     req->overlap_bytes = MAX(req->overlap_bytes, overlap_bytes);
-    waited = bdrv_wait_serialising_requests_locked(bs, req);
-    qemu_co_mutex_unlock(&bs->reqs_lock);
-    return waited;
 }
 
 /**
@@ -892,12 +899,27 @@
     }
 
     qemu_co_mutex_lock(&bs->reqs_lock);
-    waited = bdrv_wait_serialising_requests_locked(bs, self);
+    waited = bdrv_wait_serialising_requests_locked(self);
     qemu_co_mutex_unlock(&bs->reqs_lock);
 
     return waited;
 }
 
+bool coroutine_fn bdrv_make_request_serialising(BdrvTrackedRequest *req,
+                                                uint64_t align)
+{
+    bool waited;
+
+    qemu_co_mutex_lock(&req->bs->reqs_lock);
+
+    tracked_request_set_serialising(req, align);
+    waited = bdrv_wait_serialising_requests_locked(req);
+
+    qemu_co_mutex_unlock(&req->bs->reqs_lock);
+
+    return waited;
+}
+
 int bdrv_check_request(int64_t offset, int64_t bytes)
 {
     if (offset < 0 || bytes < 0) {
@@ -1423,7 +1445,7 @@
          * with each other for the same cluster.  For example, in copy-on-read
          * it ensures that the CoR read and write operations are atomic and
          * guest writes cannot interleave between them. */
-        bdrv_mark_request_serialising(req, bdrv_get_cluster_size(bs));
+        bdrv_make_request_serialising(req, bdrv_get_cluster_size(bs));
     } else {
         bdrv_wait_serialising_requests(req);
     }
@@ -1827,7 +1849,6 @@
                           BdrvTrackedRequest *req, int flags)
 {
     BlockDriverState *bs = child->bs;
-    bool waited;
     int64_t end_sector = DIV_ROUND_UP(offset + bytes, BDRV_SECTOR_SIZE);
 
     if (bs->read_only) {
@@ -1837,17 +1858,18 @@
     assert(!(bs->open_flags & BDRV_O_INACTIVE));
     assert((bs->open_flags & BDRV_O_NO_IO) == 0);
     assert(!(flags & ~BDRV_REQ_MASK));
+    assert(!((flags & BDRV_REQ_NO_WAIT) && !(flags & BDRV_REQ_SERIALISING)));
 
     if (flags & BDRV_REQ_SERIALISING) {
-        waited = bdrv_mark_request_serialising(req, bdrv_get_cluster_size(bs));
-        /*
-         * For a misaligned request we should have already waited earlier,
-         * because we come after bdrv_padding_rmw_read which must be called
-         * with the request already marked as serialising.
-         */
-        assert(!waited ||
-               (req->offset == req->overlap_offset &&
-                req->bytes == req->overlap_bytes));
+        QEMU_LOCK_GUARD(&bs->reqs_lock);
+
+        tracked_request_set_serialising(req, bdrv_get_cluster_size(bs));
+
+        if ((flags & BDRV_REQ_NO_WAIT) && bdrv_find_conflicting_request(req)) {
+            return -EBUSY;
+        }
+
+        bdrv_wait_serialising_requests_locked(req);
     } else {
         bdrv_wait_serialising_requests(req);
     }
@@ -2013,7 +2035,7 @@
 
     padding = bdrv_init_padding(bs, offset, bytes, &pad);
     if (padding) {
-        bdrv_mark_request_serialising(req, align);
+        bdrv_make_request_serialising(req, align);
 
         bdrv_padding_rmw_read(child, req, &pad, true);
 
@@ -2127,7 +2149,7 @@
     }
 
     if (bdrv_pad_request(bs, &qiov, &qiov_offset, &offset, &bytes, &pad)) {
-        bdrv_mark_request_serialising(&req, align);
+        bdrv_make_request_serialising(&req, align);
         bdrv_padding_rmw_read(child, &req, &pad, false);
     }
 
@@ -3248,7 +3270,7 @@
      * new area, we need to make sure that no write requests are made to it
      * concurrently or they might be overwritten by preallocation. */
     if (new_bytes) {
-        bdrv_mark_request_serialising(&req, 1);
+        bdrv_make_request_serialising(&req, 1);
     }
     if (bs->read_only) {
         error_setg(errp, "Image is read-only");
diff --git a/block/meson.build b/block/meson.build
index 5dcc1e5..7595d86 100644
--- a/block/meson.build
+++ b/block/meson.build
@@ -12,6 +12,7 @@
   'block-copy.c',
   'commit.c',
   'copy-on-read.c',
+  'preallocate.c',
   'create.c',
   'crypto.c',
   'dirty-bitmap.c',
diff --git a/block/nvme.c b/block/nvme.c
index a06a188..5a6fbac 100644
--- a/block/nvme.c
+++ b/block/nvme.c
@@ -1389,6 +1389,29 @@
 
 }
 
+static int coroutine_fn nvme_co_truncate(BlockDriverState *bs, int64_t offset,
+                                         bool exact, PreallocMode prealloc,
+                                         BdrvRequestFlags flags, Error **errp)
+{
+    int64_t cur_length;
+
+    if (prealloc != PREALLOC_MODE_OFF) {
+        error_setg(errp, "Unsupported preallocation mode '%s'",
+                   PreallocMode_str(prealloc));
+        return -ENOTSUP;
+    }
+
+    cur_length = nvme_getlength(bs);
+    if (offset != cur_length && exact) {
+        error_setg(errp, "Cannot resize NVMe devices");
+        return -ENOTSUP;
+    } else if (offset > cur_length) {
+        error_setg(errp, "Cannot grow NVMe devices");
+        return -EINVAL;
+    }
+
+    return 0;
+}
 
 static int nvme_reopen_prepare(BDRVReopenState *reopen_state,
                                BlockReopenQueue *queue, Error **errp)
@@ -1523,6 +1546,7 @@
     .bdrv_close               = nvme_close,
     .bdrv_getlength           = nvme_getlength,
     .bdrv_probe_blocksizes    = nvme_probe_blocksizes,
+    .bdrv_co_truncate         = nvme_co_truncate,
 
     .bdrv_co_preadv           = nvme_co_preadv,
     .bdrv_co_pwritev          = nvme_co_pwritev,
diff --git a/block/preallocate.c b/block/preallocate.c
new file mode 100644
index 0000000..b619206
--- /dev/null
+++ b/block/preallocate.c
@@ -0,0 +1,559 @@
+/*
+ * preallocate filter driver
+ *
+ * The driver performs preallocate operation: it is injected above
+ * some node, and before each write over EOF it does additional preallocating
+ * write-zeroes request.
+ *
+ * Copyright (c) 2020 Virtuozzo International GmbH.
+ *
+ * Author:
+ *  Sementsov-Ogievskiy Vladimir <vsementsov@virtuozzo.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "qemu/osdep.h"
+
+#include "qapi/error.h"
+#include "qemu/module.h"
+#include "qemu/option.h"
+#include "qemu/units.h"
+#include "block/block_int.h"
+
+
+typedef struct PreallocateOpts {
+    int64_t prealloc_size;
+    int64_t prealloc_align;
+} PreallocateOpts;
+
+typedef struct BDRVPreallocateState {
+    PreallocateOpts opts;
+
+    /*
+     * Track real data end, to crop preallocation on close. If < 0 the status is
+     * unknown.
+     *
+     * @data_end is a maximum of file size on open (or when we get write/resize
+     * permissions) and all write request ends after it. So it's safe to
+     * truncate to data_end if it is valid.
+     */
+    int64_t data_end;
+
+    /*
+     * Start of trailing preallocated area which reads as zero. May be smaller
+     * than data_end, if user does over-EOF write zero operation. If < 0 the
+     * status is unknown.
+     *
+     * If both @zero_start and @file_end are valid, the region
+     * [@zero_start, @file_end) is known to be preallocated zeroes. If @file_end
+     * is not valid, @zero_start doesn't make much sense.
+     */
+    int64_t zero_start;
+
+    /*
+     * Real end of file. Actually the cache for bdrv_getlength(bs->file->bs),
+     * to avoid extra lseek() calls on each write operation. If < 0 the status
+     * is unknown.
+     */
+    int64_t file_end;
+
+    /*
+     * All three states @data_end, @zero_start and @file_end are guaranteed to
+     * be invalid (< 0) when we don't have both exclusive BLK_PERM_RESIZE and
+     * BLK_PERM_WRITE permissions on file child.
+     */
+} BDRVPreallocateState;
+
+#define PREALLOCATE_OPT_PREALLOC_ALIGN "prealloc-align"
+#define PREALLOCATE_OPT_PREALLOC_SIZE "prealloc-size"
+static QemuOptsList runtime_opts = {
+    .name = "preallocate",
+    .head = QTAILQ_HEAD_INITIALIZER(runtime_opts.head),
+    .desc = {
+        {
+            .name = PREALLOCATE_OPT_PREALLOC_ALIGN,
+            .type = QEMU_OPT_SIZE,
+            .help = "on preallocation, align file length to this number, "
+                "default 1M",
+        },
+        {
+            .name = PREALLOCATE_OPT_PREALLOC_SIZE,
+            .type = QEMU_OPT_SIZE,
+            .help = "how much to preallocate, default 128M",
+        },
+        { /* end of list */ }
+    },
+};
+
+static bool preallocate_absorb_opts(PreallocateOpts *dest, QDict *options,
+                                    BlockDriverState *child_bs, Error **errp)
+{
+    QemuOpts *opts = qemu_opts_create(&runtime_opts, NULL, 0, &error_abort);
+
+    if (!qemu_opts_absorb_qdict(opts, options, errp)) {
+        return false;
+    }
+
+    dest->prealloc_align =
+        qemu_opt_get_size(opts, PREALLOCATE_OPT_PREALLOC_ALIGN, 1 * MiB);
+    dest->prealloc_size =
+        qemu_opt_get_size(opts, PREALLOCATE_OPT_PREALLOC_SIZE, 128 * MiB);
+
+    qemu_opts_del(opts);
+
+    if (!QEMU_IS_ALIGNED(dest->prealloc_align, BDRV_SECTOR_SIZE)) {
+        error_setg(errp, "prealloc-align parameter of preallocate filter "
+                   "is not aligned to %llu", BDRV_SECTOR_SIZE);
+        return false;
+    }
+
+    if (!QEMU_IS_ALIGNED(dest->prealloc_align,
+                         child_bs->bl.request_alignment)) {
+        error_setg(errp, "prealloc-align parameter of preallocate filter "
+                   "is not aligned to underlying node request alignment "
+                   "(%" PRIi32 ")", child_bs->bl.request_alignment);
+        return false;
+    }
+
+    return true;
+}
+
+static int preallocate_open(BlockDriverState *bs, QDict *options, int flags,
+                            Error **errp)
+{
+    BDRVPreallocateState *s = bs->opaque;
+
+    /*
+     * s->data_end and friends should be initialized on permission update.
+     * For this to work, mark them invalid.
+     */
+    s->file_end = s->zero_start = s->data_end = -EINVAL;
+
+    bs->file = bdrv_open_child(NULL, options, "file", bs, &child_of_bds,
+                               BDRV_CHILD_FILTERED | BDRV_CHILD_PRIMARY,
+                               false, errp);
+    if (!bs->file) {
+        return -EINVAL;
+    }
+
+    if (!preallocate_absorb_opts(&s->opts, options, bs->file->bs, errp)) {
+        return -EINVAL;
+    }
+
+    bs->supported_write_flags = BDRV_REQ_WRITE_UNCHANGED |
+        (BDRV_REQ_FUA & bs->file->bs->supported_write_flags);
+
+    bs->supported_zero_flags = BDRV_REQ_WRITE_UNCHANGED |
+        ((BDRV_REQ_FUA | BDRV_REQ_MAY_UNMAP | BDRV_REQ_NO_FALLBACK) &
+            bs->file->bs->supported_zero_flags);
+
+    return 0;
+}
+
+static void preallocate_close(BlockDriverState *bs)
+{
+    int ret;
+    BDRVPreallocateState *s = bs->opaque;
+
+    if (s->data_end < 0) {
+        return;
+    }
+
+    if (s->file_end < 0) {
+        s->file_end = bdrv_getlength(bs->file->bs);
+        if (s->file_end < 0) {
+            return;
+        }
+    }
+
+    if (s->data_end < s->file_end) {
+        ret = bdrv_truncate(bs->file, s->data_end, true, PREALLOC_MODE_OFF, 0,
+                            NULL);
+        s->file_end = ret < 0 ? ret : s->data_end;
+    }
+}
+
+
+/*
+ * Handle reopen.
+ *
+ * We must implement reopen handlers, otherwise reopen just don't work. Handle
+ * new options and don't care about preallocation state, as it is handled in
+ * set/check permission handlers.
+ */
+
+static int preallocate_reopen_prepare(BDRVReopenState *reopen_state,
+                                      BlockReopenQueue *queue, Error **errp)
+{
+    PreallocateOpts *opts = g_new0(PreallocateOpts, 1);
+
+    if (!preallocate_absorb_opts(opts, reopen_state->options,
+                                 reopen_state->bs->file->bs, errp)) {
+        g_free(opts);
+        return -EINVAL;
+    }
+
+    reopen_state->opaque = opts;
+
+    return 0;
+}
+
+static void preallocate_reopen_commit(BDRVReopenState *state)
+{
+    BDRVPreallocateState *s = state->bs->opaque;
+
+    s->opts = *(PreallocateOpts *)state->opaque;
+
+    g_free(state->opaque);
+    state->opaque = NULL;
+}
+
+static void preallocate_reopen_abort(BDRVReopenState *state)
+{
+    g_free(state->opaque);
+    state->opaque = NULL;
+}
+
+static coroutine_fn int preallocate_co_preadv_part(
+        BlockDriverState *bs, uint64_t offset, uint64_t bytes,
+        QEMUIOVector *qiov, size_t qiov_offset, int flags)
+{
+    return bdrv_co_preadv_part(bs->file, offset, bytes, qiov, qiov_offset,
+                               flags);
+}
+
+static int coroutine_fn preallocate_co_pdiscard(BlockDriverState *bs,
+                                               int64_t offset, int bytes)
+{
+    return bdrv_co_pdiscard(bs->file, offset, bytes);
+}
+
+static bool can_write_resize(uint64_t perm)
+{
+    return (perm & BLK_PERM_WRITE) && (perm & BLK_PERM_RESIZE);
+}
+
+static bool has_prealloc_perms(BlockDriverState *bs)
+{
+    BDRVPreallocateState *s = bs->opaque;
+
+    if (can_write_resize(bs->file->perm)) {
+        assert(!(bs->file->shared_perm & BLK_PERM_WRITE));
+        assert(!(bs->file->shared_perm & BLK_PERM_RESIZE));
+        return true;
+    }
+
+    assert(s->data_end < 0);
+    assert(s->zero_start < 0);
+    assert(s->file_end < 0);
+    return false;
+}
+
+/*
+ * Call on each write. Returns true if @want_merge_zero is true and the region
+ * [offset, offset + bytes) is zeroed (as a result of this call or earlier
+ * preallocation).
+ *
+ * want_merge_zero is used to merge write-zero request with preallocation in
+ * one bdrv_co_pwrite_zeroes() call.
+ */
+static bool coroutine_fn handle_write(BlockDriverState *bs, int64_t offset,
+                                      int64_t bytes, bool want_merge_zero)
+{
+    BDRVPreallocateState *s = bs->opaque;
+    int64_t end = offset + bytes;
+    int64_t prealloc_start, prealloc_end;
+    int ret;
+
+    if (!has_prealloc_perms(bs)) {
+        /* We don't have state neither should try to recover it */
+        return false;
+    }
+
+    if (s->data_end < 0) {
+        s->data_end = bdrv_getlength(bs->file->bs);
+        if (s->data_end < 0) {
+            return false;
+        }
+
+        if (s->file_end < 0) {
+            s->file_end = s->data_end;
+        }
+    }
+
+    if (end <= s->data_end) {
+        return false;
+    }
+
+    /* We have valid s->data_end, and request writes beyond it. */
+
+    s->data_end = end;
+    if (s->zero_start < 0 || !want_merge_zero) {
+        s->zero_start = end;
+    }
+
+    if (s->file_end < 0) {
+        s->file_end = bdrv_getlength(bs->file->bs);
+        if (s->file_end < 0) {
+            return false;
+        }
+    }
+
+    /* Now s->data_end, s->zero_start and s->file_end are valid. */
+
+    if (end <= s->file_end) {
+        /* No preallocation needed. */
+        return want_merge_zero && offset >= s->zero_start;
+    }
+
+    /* Now we want new preallocation, as request writes beyond s->file_end. */
+
+    prealloc_start = want_merge_zero ? MIN(offset, s->file_end) : s->file_end;
+    prealloc_end = QEMU_ALIGN_UP(end + s->opts.prealloc_size,
+                                 s->opts.prealloc_align);
+
+    ret = bdrv_co_pwrite_zeroes(
+            bs->file, prealloc_start, prealloc_end - prealloc_start,
+            BDRV_REQ_NO_FALLBACK | BDRV_REQ_SERIALISING | BDRV_REQ_NO_WAIT);
+    if (ret < 0) {
+        s->file_end = ret;
+        return false;
+    }
+
+    s->file_end = prealloc_end;
+    return want_merge_zero;
+}
+
+static int coroutine_fn preallocate_co_pwrite_zeroes(BlockDriverState *bs,
+        int64_t offset, int bytes, BdrvRequestFlags flags)
+{
+    bool want_merge_zero =
+        !(flags & ~(BDRV_REQ_ZERO_WRITE | BDRV_REQ_NO_FALLBACK));
+    if (handle_write(bs, offset, bytes, want_merge_zero)) {
+        return 0;
+    }
+
+    return bdrv_co_pwrite_zeroes(bs->file, offset, bytes, flags);
+}
+
+static coroutine_fn int preallocate_co_pwritev_part(BlockDriverState *bs,
+                                                    uint64_t offset,
+                                                    uint64_t bytes,
+                                                    QEMUIOVector *qiov,
+                                                    size_t qiov_offset,
+                                                    int flags)
+{
+    handle_write(bs, offset, bytes, false);
+
+    return bdrv_co_pwritev_part(bs->file, offset, bytes, qiov, qiov_offset,
+                                flags);
+}
+
+static int coroutine_fn
+preallocate_co_truncate(BlockDriverState *bs, int64_t offset,
+                        bool exact, PreallocMode prealloc,
+                        BdrvRequestFlags flags, Error **errp)
+{
+    ERRP_GUARD();
+    BDRVPreallocateState *s = bs->opaque;
+    int ret;
+
+    if (s->data_end >= 0 && offset > s->data_end) {
+        if (s->file_end < 0) {
+            s->file_end = bdrv_getlength(bs->file->bs);
+            if (s->file_end < 0) {
+                error_setg(errp, "failed to get file length");
+                return s->file_end;
+            }
+        }
+
+        if (prealloc == PREALLOC_MODE_FALLOC) {
+            /*
+             * If offset <= s->file_end, the task is already done, just
+             * update s->data_end, to move part of "filter preallocation"
+             * to "preallocation requested by user".
+             * Otherwise just proceed to preallocate missing part.
+             */
+            if (offset <= s->file_end) {
+                s->data_end = offset;
+                return 0;
+            }
+        } else {
+            /*
+             * We have to drop our preallocation, to
+             * - avoid "Cannot use preallocation for shrinking files" in
+             *   case of offset < file_end
+             * - give PREALLOC_MODE_OFF a chance to keep small disk
+             *   usage
+             * - give PREALLOC_MODE_FULL a chance to actually write the
+             *   whole region as user expects
+             */
+            if (s->file_end > s->data_end) {
+                ret = bdrv_co_truncate(bs->file, s->data_end, true,
+                                       PREALLOC_MODE_OFF, 0, errp);
+                if (ret < 0) {
+                    s->file_end = ret;
+                    error_prepend(errp, "preallocate-filter: failed to drop "
+                                  "write-zero preallocation: ");
+                    return ret;
+                }
+                s->file_end = s->data_end;
+            }
+        }
+
+        s->data_end = offset;
+    }
+
+    ret = bdrv_co_truncate(bs->file, offset, exact, prealloc, flags, errp);
+    if (ret < 0) {
+        s->file_end = s->zero_start = s->data_end = ret;
+        return ret;
+    }
+
+    if (has_prealloc_perms(bs)) {
+        s->file_end = s->zero_start = s->data_end = offset;
+    }
+    return 0;
+}
+
+static int coroutine_fn preallocate_co_flush(BlockDriverState *bs)
+{
+    return bdrv_co_flush(bs->file->bs);
+}
+
+static int64_t preallocate_getlength(BlockDriverState *bs)
+{
+    int64_t ret;
+    BDRVPreallocateState *s = bs->opaque;
+
+    if (s->data_end >= 0) {
+        return s->data_end;
+    }
+
+    ret = bdrv_getlength(bs->file->bs);
+
+    if (has_prealloc_perms(bs)) {
+        s->file_end = s->zero_start = s->data_end = ret;
+    }
+
+    return ret;
+}
+
+static int preallocate_check_perm(BlockDriverState *bs,
+                                  uint64_t perm, uint64_t shared, Error **errp)
+{
+    BDRVPreallocateState *s = bs->opaque;
+
+    if (s->data_end >= 0 && !can_write_resize(perm)) {
+        /*
+         * Lose permissions.
+         * We should truncate in check_perm, as in set_perm bs->file->perm will
+         * be already changed, and we should not violate it.
+         */
+        if (s->file_end < 0) {
+            s->file_end = bdrv_getlength(bs->file->bs);
+            if (s->file_end < 0) {
+                error_setg(errp, "Failed to get file length");
+                return s->file_end;
+            }
+        }
+
+        if (s->data_end < s->file_end) {
+            int ret = bdrv_truncate(bs->file, s->data_end, true,
+                                    PREALLOC_MODE_OFF, 0, NULL);
+            if (ret < 0) {
+                error_setg(errp, "Failed to drop preallocation");
+                s->file_end = ret;
+                return ret;
+            }
+            s->file_end = s->data_end;
+        }
+    }
+
+    return 0;
+}
+
+static void preallocate_set_perm(BlockDriverState *bs,
+                                 uint64_t perm, uint64_t shared)
+{
+    BDRVPreallocateState *s = bs->opaque;
+
+    if (can_write_resize(perm)) {
+        if (s->data_end < 0) {
+            s->data_end = s->file_end = s->zero_start =
+                bdrv_getlength(bs->file->bs);
+        }
+    } else {
+        /*
+         * We drop our permissions, as well as allow shared
+         * permissions (see preallocate_child_perm), anyone will be able to
+         * change the child, so mark all states invalid. We'll regain control if
+         * get good permissions back.
+         */
+        s->data_end = s->file_end = s->zero_start = -EINVAL;
+    }
+}
+
+static void preallocate_child_perm(BlockDriverState *bs, BdrvChild *c,
+    BdrvChildRole role, BlockReopenQueue *reopen_queue,
+    uint64_t perm, uint64_t shared, uint64_t *nperm, uint64_t *nshared)
+{
+    bdrv_default_perms(bs, c, role, reopen_queue, perm, shared, nperm, nshared);
+
+    if (can_write_resize(perm)) {
+        /* This should come by default, but let's enforce: */
+        *nperm |= BLK_PERM_WRITE | BLK_PERM_RESIZE;
+
+        /*
+         * Don't share, to keep our states s->file_end, s->data_end and
+         * s->zero_start valid.
+         */
+        *nshared &= ~(BLK_PERM_WRITE | BLK_PERM_RESIZE);
+    }
+}
+
+BlockDriver bdrv_preallocate_filter = {
+    .format_name = "preallocate",
+    .instance_size = sizeof(BDRVPreallocateState),
+
+    .bdrv_getlength = preallocate_getlength,
+    .bdrv_open = preallocate_open,
+    .bdrv_close = preallocate_close,
+
+    .bdrv_reopen_prepare  = preallocate_reopen_prepare,
+    .bdrv_reopen_commit   = preallocate_reopen_commit,
+    .bdrv_reopen_abort    = preallocate_reopen_abort,
+
+    .bdrv_co_preadv_part = preallocate_co_preadv_part,
+    .bdrv_co_pwritev_part = preallocate_co_pwritev_part,
+    .bdrv_co_pwrite_zeroes = preallocate_co_pwrite_zeroes,
+    .bdrv_co_pdiscard = preallocate_co_pdiscard,
+    .bdrv_co_flush = preallocate_co_flush,
+    .bdrv_co_truncate = preallocate_co_truncate,
+
+    .bdrv_check_perm = preallocate_check_perm,
+    .bdrv_set_perm = preallocate_set_perm,
+    .bdrv_child_perm = preallocate_child_perm,
+
+    .has_variable_length = true,
+    .is_filter = true,
+};
+
+static void bdrv_preallocate_init(void)
+{
+    bdrv_register(&bdrv_preallocate_filter);
+}
+
+block_init(bdrv_preallocate_init);
diff --git a/block/quorum.c b/block/quorum.c
index 4b08a19..0bd7545 100644
--- a/block/quorum.c
+++ b/block/quorum.c
@@ -18,6 +18,7 @@
 #include "qemu/module.h"
 #include "qemu/option.h"
 #include "block/block_int.h"
+#include "block/coroutines.h"
 #include "block/qdict.h"
 #include "qapi/error.h"
 #include "qapi/qapi-events-block.h"
@@ -691,8 +692,13 @@
     QuorumChildRequest *sacb = &acb->qcrs[i];
 
     sacb->bs = s->children[i]->bs;
-    sacb->ret = bdrv_co_pwritev(s->children[i], acb->offset, acb->bytes,
-                                acb->qiov, acb->flags);
+    if (acb->flags & BDRV_REQ_ZERO_WRITE) {
+        sacb->ret = bdrv_co_pwrite_zeroes(s->children[i], acb->offset,
+                                          acb->bytes, acb->flags);
+    } else {
+        sacb->ret = bdrv_co_pwritev(s->children[i], acb->offset, acb->bytes,
+                                    acb->qiov, acb->flags);
+    }
     if (sacb->ret == 0) {
         acb->success_count++;
     } else {
@@ -738,6 +744,14 @@
     return ret;
 }
 
+static int quorum_co_pwrite_zeroes(BlockDriverState *bs, int64_t offset,
+                                   int bytes, BdrvRequestFlags flags)
+
+{
+    return quorum_co_pwritev(bs, offset, bytes, NULL,
+                             flags | BDRV_REQ_ZERO_WRITE);
+}
+
 static int64_t quorum_getlength(BlockDriverState *bs)
 {
     BDRVQuorumState *s = bs->opaque;
@@ -896,6 +910,21 @@
     },
 };
 
+static void quorum_refresh_flags(BlockDriverState *bs)
+{
+    BDRVQuorumState *s = bs->opaque;
+    int i;
+
+    bs->supported_zero_flags =
+        BDRV_REQ_FUA | BDRV_REQ_MAY_UNMAP | BDRV_REQ_NO_FALLBACK;
+
+    for (i = 0; i < s->num_children; i++) {
+        bs->supported_zero_flags &= s->children[i]->bs->supported_zero_flags;
+    }
+
+    bs->supported_zero_flags |= BDRV_REQ_WRITE_UNCHANGED;
+}
+
 static int quorum_open(BlockDriverState *bs, QDict *options, int flags,
                        Error **errp)
 {
@@ -990,6 +1019,7 @@
     s->next_child_index = s->num_children;
 
     bs->supported_write_flags = BDRV_REQ_WRITE_UNCHANGED;
+    quorum_refresh_flags(bs);
 
     g_free(opened);
     goto exit;
@@ -1061,6 +1091,7 @@
     }
     s->children = g_renew(BdrvChild *, s->children, s->num_children + 1);
     s->children[s->num_children++] = child;
+    quorum_refresh_flags(bs);
 
 out:
     bdrv_drained_end(bs);
@@ -1105,6 +1136,7 @@
     s->children = g_renew(BdrvChild *, s->children, --s->num_children);
     bdrv_unref_child(bs, child);
 
+    quorum_refresh_flags(bs);
     bdrv_drained_end(bs);
 }
 
@@ -1179,6 +1211,56 @@
              | DEFAULT_PERM_UNCHANGED;
 }
 
+/*
+ * Each one of the children can report different status flags even
+ * when they contain the same data, so what this function does is
+ * return BDRV_BLOCK_ZERO if *all* children agree that a certain
+ * region contains zeroes, and BDRV_BLOCK_DATA otherwise.
+ */
+static int coroutine_fn quorum_co_block_status(BlockDriverState *bs,
+                                               bool want_zero,
+                                               int64_t offset, int64_t count,
+                                               int64_t *pnum, int64_t *map,
+                                               BlockDriverState **file)
+{
+    BDRVQuorumState *s = bs->opaque;
+    int i, ret;
+    int64_t pnum_zero = count;
+    int64_t pnum_data = 0;
+
+    for (i = 0; i < s->num_children; i++) {
+        int64_t bytes;
+        ret = bdrv_co_common_block_status_above(s->children[i]->bs, NULL, false,
+                                                want_zero, offset, count,
+                                                &bytes, NULL, NULL, NULL);
+        if (ret < 0) {
+            quorum_report_bad(QUORUM_OP_TYPE_READ, offset, count,
+                              s->children[i]->bs->node_name, ret);
+            pnum_data = count;
+            break;
+        }
+        /*
+         * Even if all children agree about whether there are zeroes
+         * or not at @offset they might disagree on the size, so use
+         * the smallest when reporting BDRV_BLOCK_ZERO and the largest
+         * when reporting BDRV_BLOCK_DATA.
+         */
+        if (ret & BDRV_BLOCK_ZERO) {
+            pnum_zero = MIN(pnum_zero, bytes);
+        } else {
+            pnum_data = MAX(pnum_data, bytes);
+        }
+    }
+
+    if (pnum_data) {
+        *pnum = pnum_data;
+        return BDRV_BLOCK_DATA;
+    } else {
+        *pnum = pnum_zero;
+        return BDRV_BLOCK_ZERO;
+    }
+}
+
 static const char *const quorum_strong_runtime_opts[] = {
     QUORUM_OPT_VOTE_THRESHOLD,
     QUORUM_OPT_BLKVERIFY,
@@ -1197,6 +1279,7 @@
     .bdrv_close                         = quorum_close,
     .bdrv_gather_child_options          = quorum_gather_child_options,
     .bdrv_dirname                       = quorum_dirname,
+    .bdrv_co_block_status               = quorum_co_block_status,
 
     .bdrv_co_flush_to_disk              = quorum_co_flush,
 
@@ -1204,6 +1287,7 @@
 
     .bdrv_co_preadv                     = quorum_co_preadv,
     .bdrv_co_pwritev                    = quorum_co_pwritev,
+    .bdrv_co_pwrite_zeroes              = quorum_co_pwrite_zeroes,
 
     .bdrv_add_child                     = quorum_add_child,
     .bdrv_del_child                     = quorum_del_child,
diff --git a/docs/system/qemu-block-drivers.rst.inc b/docs/system/qemu-block-drivers.rst.inc
index b052a6d..60a064b 100644
--- a/docs/system/qemu-block-drivers.rst.inc
+++ b/docs/system/qemu-block-drivers.rst.inc
@@ -952,3 +952,29 @@
 More than one byte could be locked by the QEMU instance, each byte of which
 reflects a particular permission that is acquired or protected by the running
 block driver.
+
+Filter drivers
+~~~~~~~~~~~~~~
+
+QEMU supports several filter drivers, which don't store any data, but perform
+some additional tasks, hooking io requests.
+
+.. program:: filter-drivers
+.. option:: preallocate
+
+  The preallocate filter driver is intended to be inserted between format
+  and protocol nodes and preallocates some additional space
+  (expanding the protocol file) when writing past the file’s end. This can be
+  useful for file-systems with slow allocation.
+
+  Supported options:
+
+  .. program:: preallocate
+  .. option:: prealloc-align
+
+    On preallocation, align the file length to this value (in bytes), default 1M.
+
+  .. program:: preallocate
+  .. option:: prealloc-size
+
+    How much to preallocate (in bytes), default 128M.
diff --git a/include/block/block.h b/include/block/block.h
index 5b81e33..a193545 100644
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -63,16 +63,7 @@
      * content. */
     BDRV_REQ_WRITE_UNCHANGED    = 0x40,
 
-    /*
-     * BDRV_REQ_SERIALISING forces request serialisation for writes.
-     * It is used to ensure that writes to the backing file of a backup process
-     * target cannot race with a read of the backup target that defers to the
-     * backing file.
-     *
-     * Note, that BDRV_REQ_SERIALISING is _not_ opposite in meaning to
-     * BDRV_REQ_NO_SERIALISING. A more descriptive name for the latter might be
-     * _DO_NOT_WAIT_FOR_SERIALISING, except that is too long.
-     */
+    /* Forces request serialisation. Use only with write requests. */
     BDRV_REQ_SERIALISING        = 0x80,
 
     /* Execute the request only if the operation can be offloaded or otherwise
@@ -86,8 +77,15 @@
      * written to qiov parameter which may be NULL.
      */
     BDRV_REQ_PREFETCH  = 0x200,
+
+    /*
+     * If we need to wait for other requests, just fail immediately. Used
+     * only together with BDRV_REQ_SERIALISING.
+     */
+    BDRV_REQ_NO_WAIT = 0x400,
+
     /* Mask of valid flags */
-    BDRV_REQ_MASK               = 0x3ff,
+    BDRV_REQ_MASK               = 0x7ff,
 } BdrvRequestFlags;
 
 typedef struct BlockSizes {
diff --git a/include/block/block_int.h b/include/block/block_int.h
index 1eeafc1..b9ef61f 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -1060,7 +1060,8 @@
 void bdrv_apply_subtree_drain(BdrvChild *child, BlockDriverState *new_parent);
 void bdrv_unapply_subtree_drain(BdrvChild *child, BlockDriverState *old_parent);
 
-bool coroutine_fn bdrv_mark_request_serialising(BdrvTrackedRequest *req, uint64_t align);
+bool coroutine_fn bdrv_make_request_serialising(BdrvTrackedRequest *req,
+                                                uint64_t align);
 BdrvTrackedRequest *coroutine_fn bdrv_co_get_self_request(BlockDriverState *bs);
 
 int get_tmp_filename(char *filename, int size);
diff --git a/qapi/block-core.json b/qapi/block-core.json
index 04c5196..3484986 100644
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -2829,7 +2829,7 @@
             'cloop', 'compress', 'copy-on-read', 'dmg', 'file', 'ftp', 'ftps',
             'gluster', 'host_cdrom', 'host_device', 'http', 'https', 'iscsi',
             'luks', 'nbd', 'nfs', 'null-aio', 'null-co', 'nvme', 'parallels',
-            'qcow', 'qcow2', 'qed', 'quorum', 'raw', 'rbd',
+            'preallocate', 'qcow', 'qcow2', 'qed', 'quorum', 'raw', 'rbd',
             { 'name': 'replication', 'if': 'defined(CONFIG_REPLICATION)' },
             'sheepdog',
             'ssh', 'throttle', 'vdi', 'vhdx', 'vmdk', 'vpc', 'vvfat' ] }
@@ -3099,6 +3099,23 @@
             'luks': 'QCryptoBlockOptionsLUKS'} }
 
 ##
+# @BlockdevOptionsPreallocate:
+#
+# Filter driver intended to be inserted between format and protocol node
+# and do preallocation in protocol node on write.
+#
+# @prealloc-align: on preallocation, align file length to this number,
+#                  default 1048576 (1M)
+#
+# @prealloc-size: how much to preallocate, default 134217728 (128M)
+#
+# Since: 6.0
+##
+{ 'struct': 'BlockdevOptionsPreallocate',
+  'base': 'BlockdevOptionsGenericFormat',
+  'data': { '*prealloc-align': 'int', '*prealloc-size': 'int' } }
+
+##
 # @BlockdevOptionsQcow2:
 #
 # Driver specific block device options for qcow2.
@@ -4006,6 +4023,7 @@
       'null-co':    'BlockdevOptionsNull',
       'nvme':       'BlockdevOptionsNVMe',
       'parallels':  'BlockdevOptionsGenericFormat',
+      'preallocate':'BlockdevOptionsPreallocate',
       'qcow2':      'BlockdevOptionsQcow2',
       'qcow':       'BlockdevOptionsQcow',
       'qed':        'BlockdevOptionsGenericCOWFormat',
diff --git a/qemu-io-cmds.c b/qemu-io-cmds.c
index 4153f1c..9761196 100644
--- a/qemu-io-cmds.c
+++ b/qemu-io-cmds.c
@@ -1698,13 +1698,42 @@
     .oneline    = "flush all in-core file state to disk",
 };
 
+static int truncate_f(BlockBackend *blk, int argc, char **argv);
+static const cmdinfo_t truncate_cmd = {
+    .name       = "truncate",
+    .altname    = "t",
+    .cfunc      = truncate_f,
+    .perm       = BLK_PERM_WRITE | BLK_PERM_RESIZE,
+    .argmin     = 1,
+    .argmax     = 3,
+    .args       = "[-m prealloc_mode] off",
+    .oneline    = "truncates the current file at the given offset",
+};
+
 static int truncate_f(BlockBackend *blk, int argc, char **argv)
 {
     Error *local_err = NULL;
     int64_t offset;
-    int ret;
+    int c, ret;
+    PreallocMode prealloc = PREALLOC_MODE_OFF;
 
-    offset = cvtnum(argv[1]);
+    while ((c = getopt(argc, argv, "m:")) != -1) {
+        switch (c) {
+        case 'm':
+            prealloc = qapi_enum_parse(&PreallocMode_lookup, optarg,
+                                       PREALLOC_MODE__MAX, NULL);
+            if (prealloc == PREALLOC_MODE__MAX) {
+                error_report("Invalid preallocation mode '%s'", optarg);
+                return -EINVAL;
+            }
+            break;
+        default:
+            qemuio_command_usage(&truncate_cmd);
+            return -EINVAL;
+        }
+    }
+
+    offset = cvtnum(argv[optind]);
     if (offset < 0) {
         print_cvtnum_err(offset, argv[1]);
         return offset;
@@ -1715,7 +1744,7 @@
      * exact=true.  It is better to err on the "emit more errors" side
      * than to be overly permissive.
      */
-    ret = blk_truncate(blk, offset, false, PREALLOC_MODE_OFF, 0, &local_err);
+    ret = blk_truncate(blk, offset, false, prealloc, 0, &local_err);
     if (ret < 0) {
         error_report_err(local_err);
         return ret;
@@ -1724,17 +1753,6 @@
     return 0;
 }
 
-static const cmdinfo_t truncate_cmd = {
-    .name       = "truncate",
-    .altname    = "t",
-    .cfunc      = truncate_f,
-    .perm       = BLK_PERM_WRITE | BLK_PERM_RESIZE,
-    .argmin     = 1,
-    .argmax     = 1,
-    .args       = "off",
-    .oneline    = "truncates the current file at the given offset",
-};
-
 static int length_f(BlockBackend *blk, int argc, char **argv)
 {
     int64_t size;
diff --git a/scripts/simplebench/bench-example.py b/scripts/simplebench/bench-example.py
index c642a5b..d9c7f7b 100644
--- a/scripts/simplebench/bench-example.py
+++ b/scripts/simplebench/bench-example.py
@@ -19,6 +19,7 @@
 #
 
 import simplebench
+from results_to_text import results_to_text
 from bench_block_job import bench_block_copy, drv_file, drv_nbd
 
 
@@ -77,4 +78,4 @@
 ]
 
 result = simplebench.bench(bench_func, test_envs, test_cases, count=3)
-print(simplebench.ascii(result))
+print(results_to_text(result))
diff --git a/scripts/simplebench/bench_prealloc.py b/scripts/simplebench/bench_prealloc.py
new file mode 100755
index 0000000..85f588c
--- /dev/null
+++ b/scripts/simplebench/bench_prealloc.py
@@ -0,0 +1,132 @@
+#!/usr/bin/env python3
+#
+# Benchmark preallocate filter
+#
+# Copyright (c) 2020 Virtuozzo International GmbH.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+#
+
+
+import sys
+import os
+import subprocess
+import re
+import json
+
+import simplebench
+from results_to_text import results_to_text
+
+
+def qemu_img_bench(args):
+    p = subprocess.run(args, stdout=subprocess.PIPE, stderr=subprocess.STDOUT,
+                       universal_newlines=True)
+
+    if p.returncode == 0:
+        try:
+            m = re.search(r'Run completed in (\d+.\d+) seconds.', p.stdout)
+            return {'seconds': float(m.group(1))}
+        except Exception:
+            return {'error': f'failed to parse qemu-img output: {p.stdout}'}
+    else:
+        return {'error': f'qemu-img failed: {p.returncode}: {p.stdout}'}
+
+
+def bench_func(env, case):
+    fname = f"{case['dir']}/prealloc-test.qcow2"
+    try:
+        os.remove(fname)
+    except OSError:
+        pass
+
+    subprocess.run([env['qemu-img-binary'], 'create', '-f', 'qcow2', fname,
+                   '16G'], stdout=subprocess.DEVNULL,
+                   stderr=subprocess.DEVNULL, check=True)
+
+    args = [env['qemu-img-binary'], 'bench', '-c', str(case['count']),
+            '-d', '64', '-s', case['block-size'], '-t', 'none', '-n', '-w']
+    if env['prealloc']:
+        args += ['--image-opts',
+                 'driver=qcow2,file.driver=preallocate,file.file.driver=file,'
+                 f'file.file.filename={fname}']
+    else:
+        args += ['-f', 'qcow2', fname]
+
+    return qemu_img_bench(args)
+
+
+def auto_count_bench_func(env, case):
+    case['count'] = 100
+    while True:
+        res = bench_func(env, case)
+        if 'error' in res:
+            return res
+
+        if res['seconds'] >= 1:
+            break
+
+        case['count'] *= 10
+
+    if res['seconds'] < 5:
+        case['count'] = round(case['count'] * 5 / res['seconds'])
+        res = bench_func(env, case)
+        if 'error' in res:
+            return res
+
+    res['iops'] = case['count'] / res['seconds']
+    return res
+
+
+if __name__ == '__main__':
+    if len(sys.argv) < 2:
+        print(f'USAGE: {sys.argv[0]} <qemu-img binary> '
+              'DISK_NAME:DIR_PATH ...')
+        exit(1)
+
+    qemu_img = sys.argv[1]
+
+    envs = [
+        {
+            'id': 'no-prealloc',
+            'qemu-img-binary': qemu_img,
+            'prealloc': False
+        },
+        {
+            'id': 'prealloc',
+            'qemu-img-binary': qemu_img,
+            'prealloc': True
+        }
+    ]
+
+    aligned_cases = []
+    unaligned_cases = []
+
+    for disk in sys.argv[2:]:
+        name, path = disk.split(':')
+        aligned_cases.append({
+            'id': f'{name}, aligned sequential 16k',
+            'block-size': '16k',
+            'dir': path
+        })
+        unaligned_cases.append({
+            'id': f'{name}, unaligned sequential 64k',
+            'block-size': '16k',
+            'dir': path
+        })
+
+    result = simplebench.bench(auto_count_bench_func, envs,
+                               aligned_cases + unaligned_cases, count=5)
+    print(results_to_text(result))
+    with open('results.json', 'w') as f:
+        json.dump(result, f, indent=4)
diff --git a/scripts/simplebench/bench_write_req.py b/scripts/simplebench/bench_write_req.py
index ca1178f..da601ea 100755
--- a/scripts/simplebench/bench_write_req.py
+++ b/scripts/simplebench/bench_write_req.py
@@ -26,6 +26,7 @@
 import os
 import subprocess
 import simplebench
+from results_to_text import results_to_text
 
 
 def bench_func(env, case):
@@ -167,4 +168,4 @@
 
     result = simplebench.bench(bench_func, test_envs, test_cases, count=3,
                                initial_run=False)
-    print(simplebench.ascii(result))
+    print(results_to_text(result))
diff --git a/scripts/simplebench/results_to_text.py b/scripts/simplebench/results_to_text.py
new file mode 100755
index 0000000..d561e5e
--- /dev/null
+++ b/scripts/simplebench/results_to_text.py
@@ -0,0 +1,126 @@
+#!/usr/bin/env python3
+#
+# Simple benchmarking framework
+#
+# Copyright (c) 2019 Virtuozzo International GmbH.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+#
+
+import math
+import tabulate
+
+# We want leading whitespace for difference row cells (see below)
+tabulate.PRESERVE_WHITESPACE = True
+
+
+def format_value(x, stdev):
+    stdev_pr = stdev / x * 100
+    if stdev_pr < 1.5:
+        # don't care too much
+        return f'{x:.2g}'
+    else:
+        return f'{x:.2g} ± {math.ceil(stdev_pr)}%'
+
+
+def result_to_text(result):
+    """Return text representation of bench_one() returned dict."""
+    if 'average' in result:
+        s = format_value(result['average'], result['stdev'])
+        if 'n-failed' in result:
+            s += '\n({} failed)'.format(result['n-failed'])
+        return s
+    else:
+        return 'FAILED'
+
+
+def results_dimension(results):
+    dim = None
+    for case in results['cases']:
+        for env in results['envs']:
+            res = results['tab'][case['id']][env['id']]
+            if dim is None:
+                dim = res['dimension']
+            else:
+                assert dim == res['dimension']
+
+    assert dim in ('iops', 'seconds')
+
+    return dim
+
+
+def results_to_text(results):
+    """Return text representation of bench() returned dict."""
+    n_columns = len(results['envs'])
+    named_columns = n_columns > 2
+    dim = results_dimension(results)
+    tab = []
+
+    if named_columns:
+        # Environment columns are named A, B, ...
+        tab.append([''] + [chr(ord('A') + i) for i in range(n_columns)])
+
+    tab.append([''] + [c['id'] for c in results['envs']])
+
+    for case in results['cases']:
+        row = [case['id']]
+        case_results = results['tab'][case['id']]
+        for env in results['envs']:
+            res = case_results[env['id']]
+            row.append(result_to_text(res))
+        tab.append(row)
+
+        # Add row of difference between columns. For each column starting from
+        # B we calculate difference with all previous columns.
+        row = ['', '']  # case name and first column
+        for i in range(1, n_columns):
+            cell = ''
+            env = results['envs'][i]
+            res = case_results[env['id']]
+
+            if 'average' not in res:
+                # Failed result
+                row.append(cell)
+                continue
+
+            for j in range(0, i):
+                env_j = results['envs'][j]
+                res_j = case_results[env_j['id']]
+                cell += ' '
+
+                if 'average' not in res_j:
+                    # Failed result
+                    cell += '--'
+                    continue
+
+                col_j = tab[0][j + 1] if named_columns else ''
+                diff_pr = round((res['average'] - res_j['average']) /
+                                res_j['average'] * 100)
+                cell += f' {col_j}{diff_pr:+}%'
+            row.append(cell)
+        tab.append(row)
+
+    return f'All results are in {dim}\n\n' + tabulate.tabulate(tab)
+
+
+if __name__ == '__main__':
+    import sys
+    import json
+
+    if len(sys.argv) < 2:
+        print(f'USAGE: {sys.argv[0]} results.json')
+        exit(1)
+
+    with open(sys.argv[1]) as f:
+        print(results_to_text(json.load(f)))
diff --git a/scripts/simplebench/simplebench.py b/scripts/simplebench/simplebench.py
index 59e7314..f61513a 100644
--- a/scripts/simplebench/simplebench.py
+++ b/scripts/simplebench/simplebench.py
@@ -18,15 +18,20 @@
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 #
 
+import statistics
+
 
 def bench_one(test_func, test_env, test_case, count=5, initial_run=True):
     """Benchmark one test-case
 
     test_func   -- benchmarking function with prototype
                    test_func(env, case), which takes test_env and test_case
-                   arguments and returns {'seconds': int} (which is benchmark
-                   result) on success and {'error': str} on error. Returned
-                   dict may contain any other additional fields.
+                   arguments and on success returns dict with 'seconds' or
+                   'iops' (or both) fields, specifying the benchmark result.
+                   If both 'iops' and 'seconds' provided, the 'iops' is
+                   considered the main, and 'seconds' is just an additional
+                   info. On failure test_func should return {'error': str}.
+                   Returned dict may contain any other additional fields.
     test_env    -- test environment - opaque first argument for test_func
     test_case   -- test case - opaque second argument for test_func
     count       -- how many times to call test_func, to calculate average
@@ -34,9 +39,10 @@
 
     Returns dict with the following fields:
         'runs':     list of test_func results
-        'average':  average seconds per run (exists only if at least one run
-                    succeeded)
-        'delta':    maximum delta between test_func result and the average
+        'dimension': dimension of results, may be 'seconds' or 'iops'
+        'average':  average value (iops or seconds) per run (exists only if at
+                    least one run succeeded)
+        'stdev':    standard deviation of results
                     (exists only if at least one run succeeded)
         'n-failed': number of failed runs (exists only if at least one run
                     failed)
@@ -54,29 +60,25 @@
 
     result = {'runs': runs}
 
-    successed = [r for r in runs if ('seconds' in r)]
-    if successed:
-        avg = sum(r['seconds'] for r in successed) / len(successed)
-        result['average'] = avg
-        result['delta'] = max(abs(r['seconds'] - avg) for r in successed)
+    succeeded = [r for r in runs if ('seconds' in r or 'iops' in r)]
+    if succeeded:
+        if 'iops' in succeeded[0]:
+            assert all('iops' in r for r in succeeded)
+            dim = 'iops'
+        else:
+            assert all('seconds' in r for r in succeeded)
+            assert all('iops' not in r for r in succeeded)
+            dim = 'seconds'
+        result['dimension'] = dim
+        result['average'] = statistics.mean(r[dim] for r in succeeded)
+        result['stdev'] = statistics.stdev(r[dim] for r in succeeded)
 
-    if len(successed) < count:
-        result['n-failed'] = count - len(successed)
+    if len(succeeded) < count:
+        result['n-failed'] = count - len(succeeded)
 
     return result
 
 
-def ascii_one(result):
-    """Return ASCII representation of bench_one() returned dict."""
-    if 'average' in result:
-        s = '{:.2f} +- {:.2f}'.format(result['average'], result['delta'])
-        if 'n-failed' in result:
-            s += '\n({} failed)'.format(result['n-failed'])
-        return s
-    else:
-        return 'FAILED'
-
-
 def bench(test_func, test_envs, test_cases, *args, **vargs):
     """Fill benchmark table
 
@@ -112,17 +114,3 @@
 
     print('Done')
     return results
-
-
-def ascii(results):
-    """Return ASCII representation of bench() returned dict."""
-    from tabulate import tabulate
-
-    tab = [[""] + [c['id'] for c in results['envs']]]
-    for case in results['cases']:
-        row = [case['id']]
-        for env in results['envs']:
-            row.append(ascii_one(results['tab'][case['id']][env['id']]))
-        tab.append(row)
-
-    return tabulate(tab)
diff --git a/tests/qemu-iotests/085.out b/tests/qemu-iotests/085.out
index 7fc44b1..32a193f 100644
--- a/tests/qemu-iotests/085.out
+++ b/tests/qemu-iotests/085.out
@@ -12,56 +12,135 @@
 
 === Create a single snapshot on virtio0 ===
 
-{ 'execute': 'blockdev-snapshot-sync', 'arguments': { 'device': 'virtio0', 'snapshot-file':'TEST_DIR/1-snapshot-v0.IMGFMT', 'format': 'IMGFMT' } }
+{ 'execute': 'blockdev-snapshot-sync',
+                      'arguments': { 'device': 'virtio0',
+                                     'snapshot-file':'TEST_DIR/1-snapshot-v0.IMGFMT',
+                                     'format': 'IMGFMT' } }
 Formatting 'TEST_DIR/1-snapshot-v0.qcow2', fmt=qcow2 cluster_size=65536 extended_l2=off compression_type=zlib size=134217728 backing_file=TEST_DIR/t.qcow2.1 backing_fmt=qcow2 lazy_refcounts=off refcount_bits=16
 {"return": {}}
 
 === Invalid command - missing device and nodename ===
 
-{ 'execute': 'blockdev-snapshot-sync', 'arguments': { 'snapshot-file':'TEST_DIR/1-snapshot-v0.IMGFMT', 'format': 'IMGFMT' } }
+{ 'execute': 'blockdev-snapshot-sync',
+                         'arguments': { 'snapshot-file':'TEST_DIR/1-snapshot-v0.IMGFMT',
+                                     'format': 'IMGFMT' } }
 {"error": {"class": "GenericError", "desc": "Cannot find device= nor node_name="}}
 
 === Invalid command - missing snapshot-file ===
 
-{ 'execute': 'blockdev-snapshot-sync', 'arguments': { 'device': 'virtio0', 'format': 'IMGFMT' } }
+{ 'execute': 'blockdev-snapshot-sync',
+                         'arguments': { 'device': 'virtio0',
+                                     'format': 'IMGFMT' } }
 {"error": {"class": "GenericError", "desc": "Parameter 'snapshot-file' is missing"}}
 
 
 === Create several transactional group snapshots ===
 
-{ 'execute': 'transaction', 'arguments': {'actions': [ { 'type': 'blockdev-snapshot-sync', 'data' : { 'device': 'virtio0', 'snapshot-file': 'TEST_DIR/2-snapshot-v0.IMGFMT' } }, { 'type': 'blockdev-snapshot-sync', 'data' : { 'device': 'virtio1', 'snapshot-file': 'TEST_DIR/2-snapshot-v1.IMGFMT' } } ] } }
+{ 'execute': 'transaction', 'arguments':
+           {'actions': [
+               { 'type': 'blockdev-snapshot-sync', 'data' :
+                   { 'device': 'virtio0',
+                      'snapshot-file': 'TEST_DIR/2-snapshot-v0.IMGFMT' } },
+               { 'type': 'blockdev-snapshot-sync', 'data' :
+                   { 'device': 'virtio1',
+                       'snapshot-file': 'TEST_DIR/2-snapshot-v1.IMGFMT' } } ]
+             } }
 Formatting 'TEST_DIR/2-snapshot-v0.qcow2', fmt=qcow2 cluster_size=65536 extended_l2=off compression_type=zlib size=134217728 backing_file=TEST_DIR/1-snapshot-v0.qcow2 backing_fmt=qcow2 lazy_refcounts=off refcount_bits=16
 Formatting 'TEST_DIR/2-snapshot-v1.qcow2', fmt=qcow2 cluster_size=65536 extended_l2=off compression_type=zlib size=134217728 backing_file=TEST_DIR/t.qcow2.2 backing_fmt=qcow2 lazy_refcounts=off refcount_bits=16
 {"return": {}}
-{ 'execute': 'transaction', 'arguments': {'actions': [ { 'type': 'blockdev-snapshot-sync', 'data' : { 'device': 'virtio0', 'snapshot-file': 'TEST_DIR/3-snapshot-v0.IMGFMT' } }, { 'type': 'blockdev-snapshot-sync', 'data' : { 'device': 'virtio1', 'snapshot-file': 'TEST_DIR/3-snapshot-v1.IMGFMT' } } ] } }
+{ 'execute': 'transaction', 'arguments':
+           {'actions': [
+               { 'type': 'blockdev-snapshot-sync', 'data' :
+                   { 'device': 'virtio0',
+                      'snapshot-file': 'TEST_DIR/3-snapshot-v0.IMGFMT' } },
+               { 'type': 'blockdev-snapshot-sync', 'data' :
+                   { 'device': 'virtio1',
+                       'snapshot-file': 'TEST_DIR/3-snapshot-v1.IMGFMT' } } ]
+             } }
 Formatting 'TEST_DIR/3-snapshot-v0.qcow2', fmt=qcow2 cluster_size=65536 extended_l2=off compression_type=zlib size=134217728 backing_file=TEST_DIR/2-snapshot-v0.qcow2 backing_fmt=qcow2 lazy_refcounts=off refcount_bits=16
 Formatting 'TEST_DIR/3-snapshot-v1.qcow2', fmt=qcow2 cluster_size=65536 extended_l2=off compression_type=zlib size=134217728 backing_file=TEST_DIR/2-snapshot-v1.qcow2 backing_fmt=qcow2 lazy_refcounts=off refcount_bits=16
 {"return": {}}
-{ 'execute': 'transaction', 'arguments': {'actions': [ { 'type': 'blockdev-snapshot-sync', 'data' : { 'device': 'virtio0', 'snapshot-file': 'TEST_DIR/4-snapshot-v0.IMGFMT' } }, { 'type': 'blockdev-snapshot-sync', 'data' : { 'device': 'virtio1', 'snapshot-file': 'TEST_DIR/4-snapshot-v1.IMGFMT' } } ] } }
+{ 'execute': 'transaction', 'arguments':
+           {'actions': [
+               { 'type': 'blockdev-snapshot-sync', 'data' :
+                   { 'device': 'virtio0',
+                      'snapshot-file': 'TEST_DIR/4-snapshot-v0.IMGFMT' } },
+               { 'type': 'blockdev-snapshot-sync', 'data' :
+                   { 'device': 'virtio1',
+                       'snapshot-file': 'TEST_DIR/4-snapshot-v1.IMGFMT' } } ]
+             } }
 Formatting 'TEST_DIR/4-snapshot-v0.qcow2', fmt=qcow2 cluster_size=65536 extended_l2=off compression_type=zlib size=134217728 backing_file=TEST_DIR/3-snapshot-v0.qcow2 backing_fmt=qcow2 lazy_refcounts=off refcount_bits=16
 Formatting 'TEST_DIR/4-snapshot-v1.qcow2', fmt=qcow2 cluster_size=65536 extended_l2=off compression_type=zlib size=134217728 backing_file=TEST_DIR/3-snapshot-v1.qcow2 backing_fmt=qcow2 lazy_refcounts=off refcount_bits=16
 {"return": {}}
-{ 'execute': 'transaction', 'arguments': {'actions': [ { 'type': 'blockdev-snapshot-sync', 'data' : { 'device': 'virtio0', 'snapshot-file': 'TEST_DIR/5-snapshot-v0.IMGFMT' } }, { 'type': 'blockdev-snapshot-sync', 'data' : { 'device': 'virtio1', 'snapshot-file': 'TEST_DIR/5-snapshot-v1.IMGFMT' } } ] } }
+{ 'execute': 'transaction', 'arguments':
+           {'actions': [
+               { 'type': 'blockdev-snapshot-sync', 'data' :
+                   { 'device': 'virtio0',
+                      'snapshot-file': 'TEST_DIR/5-snapshot-v0.IMGFMT' } },
+               { 'type': 'blockdev-snapshot-sync', 'data' :
+                   { 'device': 'virtio1',
+                       'snapshot-file': 'TEST_DIR/5-snapshot-v1.IMGFMT' } } ]
+             } }
 Formatting 'TEST_DIR/5-snapshot-v0.qcow2', fmt=qcow2 cluster_size=65536 extended_l2=off compression_type=zlib size=134217728 backing_file=TEST_DIR/4-snapshot-v0.qcow2 backing_fmt=qcow2 lazy_refcounts=off refcount_bits=16
 Formatting 'TEST_DIR/5-snapshot-v1.qcow2', fmt=qcow2 cluster_size=65536 extended_l2=off compression_type=zlib size=134217728 backing_file=TEST_DIR/4-snapshot-v1.qcow2 backing_fmt=qcow2 lazy_refcounts=off refcount_bits=16
 {"return": {}}
-{ 'execute': 'transaction', 'arguments': {'actions': [ { 'type': 'blockdev-snapshot-sync', 'data' : { 'device': 'virtio0', 'snapshot-file': 'TEST_DIR/6-snapshot-v0.IMGFMT' } }, { 'type': 'blockdev-snapshot-sync', 'data' : { 'device': 'virtio1', 'snapshot-file': 'TEST_DIR/6-snapshot-v1.IMGFMT' } } ] } }
+{ 'execute': 'transaction', 'arguments':
+           {'actions': [
+               { 'type': 'blockdev-snapshot-sync', 'data' :
+                   { 'device': 'virtio0',
+                      'snapshot-file': 'TEST_DIR/6-snapshot-v0.IMGFMT' } },
+               { 'type': 'blockdev-snapshot-sync', 'data' :
+                   { 'device': 'virtio1',
+                       'snapshot-file': 'TEST_DIR/6-snapshot-v1.IMGFMT' } } ]
+             } }
 Formatting 'TEST_DIR/6-snapshot-v0.qcow2', fmt=qcow2 cluster_size=65536 extended_l2=off compression_type=zlib size=134217728 backing_file=TEST_DIR/5-snapshot-v0.qcow2 backing_fmt=qcow2 lazy_refcounts=off refcount_bits=16
 Formatting 'TEST_DIR/6-snapshot-v1.qcow2', fmt=qcow2 cluster_size=65536 extended_l2=off compression_type=zlib size=134217728 backing_file=TEST_DIR/5-snapshot-v1.qcow2 backing_fmt=qcow2 lazy_refcounts=off refcount_bits=16
 {"return": {}}
-{ 'execute': 'transaction', 'arguments': {'actions': [ { 'type': 'blockdev-snapshot-sync', 'data' : { 'device': 'virtio0', 'snapshot-file': 'TEST_DIR/7-snapshot-v0.IMGFMT' } }, { 'type': 'blockdev-snapshot-sync', 'data' : { 'device': 'virtio1', 'snapshot-file': 'TEST_DIR/7-snapshot-v1.IMGFMT' } } ] } }
+{ 'execute': 'transaction', 'arguments':
+           {'actions': [
+               { 'type': 'blockdev-snapshot-sync', 'data' :
+                   { 'device': 'virtio0',
+                      'snapshot-file': 'TEST_DIR/7-snapshot-v0.IMGFMT' } },
+               { 'type': 'blockdev-snapshot-sync', 'data' :
+                   { 'device': 'virtio1',
+                       'snapshot-file': 'TEST_DIR/7-snapshot-v1.IMGFMT' } } ]
+             } }
 Formatting 'TEST_DIR/7-snapshot-v0.qcow2', fmt=qcow2 cluster_size=65536 extended_l2=off compression_type=zlib size=134217728 backing_file=TEST_DIR/6-snapshot-v0.qcow2 backing_fmt=qcow2 lazy_refcounts=off refcount_bits=16
 Formatting 'TEST_DIR/7-snapshot-v1.qcow2', fmt=qcow2 cluster_size=65536 extended_l2=off compression_type=zlib size=134217728 backing_file=TEST_DIR/6-snapshot-v1.qcow2 backing_fmt=qcow2 lazy_refcounts=off refcount_bits=16
 {"return": {}}
-{ 'execute': 'transaction', 'arguments': {'actions': [ { 'type': 'blockdev-snapshot-sync', 'data' : { 'device': 'virtio0', 'snapshot-file': 'TEST_DIR/8-snapshot-v0.IMGFMT' } }, { 'type': 'blockdev-snapshot-sync', 'data' : { 'device': 'virtio1', 'snapshot-file': 'TEST_DIR/8-snapshot-v1.IMGFMT' } } ] } }
+{ 'execute': 'transaction', 'arguments':
+           {'actions': [
+               { 'type': 'blockdev-snapshot-sync', 'data' :
+                   { 'device': 'virtio0',
+                      'snapshot-file': 'TEST_DIR/8-snapshot-v0.IMGFMT' } },
+               { 'type': 'blockdev-snapshot-sync', 'data' :
+                   { 'device': 'virtio1',
+                       'snapshot-file': 'TEST_DIR/8-snapshot-v1.IMGFMT' } } ]
+             } }
 Formatting 'TEST_DIR/8-snapshot-v0.qcow2', fmt=qcow2 cluster_size=65536 extended_l2=off compression_type=zlib size=134217728 backing_file=TEST_DIR/7-snapshot-v0.qcow2 backing_fmt=qcow2 lazy_refcounts=off refcount_bits=16
 Formatting 'TEST_DIR/8-snapshot-v1.qcow2', fmt=qcow2 cluster_size=65536 extended_l2=off compression_type=zlib size=134217728 backing_file=TEST_DIR/7-snapshot-v1.qcow2 backing_fmt=qcow2 lazy_refcounts=off refcount_bits=16
 {"return": {}}
-{ 'execute': 'transaction', 'arguments': {'actions': [ { 'type': 'blockdev-snapshot-sync', 'data' : { 'device': 'virtio0', 'snapshot-file': 'TEST_DIR/9-snapshot-v0.IMGFMT' } }, { 'type': 'blockdev-snapshot-sync', 'data' : { 'device': 'virtio1', 'snapshot-file': 'TEST_DIR/9-snapshot-v1.IMGFMT' } } ] } }
+{ 'execute': 'transaction', 'arguments':
+           {'actions': [
+               { 'type': 'blockdev-snapshot-sync', 'data' :
+                   { 'device': 'virtio0',
+                      'snapshot-file': 'TEST_DIR/9-snapshot-v0.IMGFMT' } },
+               { 'type': 'blockdev-snapshot-sync', 'data' :
+                   { 'device': 'virtio1',
+                       'snapshot-file': 'TEST_DIR/9-snapshot-v1.IMGFMT' } } ]
+             } }
 Formatting 'TEST_DIR/9-snapshot-v0.qcow2', fmt=qcow2 cluster_size=65536 extended_l2=off compression_type=zlib size=134217728 backing_file=TEST_DIR/8-snapshot-v0.qcow2 backing_fmt=qcow2 lazy_refcounts=off refcount_bits=16
 Formatting 'TEST_DIR/9-snapshot-v1.qcow2', fmt=qcow2 cluster_size=65536 extended_l2=off compression_type=zlib size=134217728 backing_file=TEST_DIR/8-snapshot-v1.qcow2 backing_fmt=qcow2 lazy_refcounts=off refcount_bits=16
 {"return": {}}
-{ 'execute': 'transaction', 'arguments': {'actions': [ { 'type': 'blockdev-snapshot-sync', 'data' : { 'device': 'virtio0', 'snapshot-file': 'TEST_DIR/10-snapshot-v0.IMGFMT' } }, { 'type': 'blockdev-snapshot-sync', 'data' : { 'device': 'virtio1', 'snapshot-file': 'TEST_DIR/10-snapshot-v1.IMGFMT' } } ] } }
+{ 'execute': 'transaction', 'arguments':
+           {'actions': [
+               { 'type': 'blockdev-snapshot-sync', 'data' :
+                   { 'device': 'virtio0',
+                      'snapshot-file': 'TEST_DIR/10-snapshot-v0.IMGFMT' } },
+               { 'type': 'blockdev-snapshot-sync', 'data' :
+                   { 'device': 'virtio1',
+                       'snapshot-file': 'TEST_DIR/10-snapshot-v1.IMGFMT' } } ]
+             } }
 Formatting 'TEST_DIR/10-snapshot-v0.qcow2', fmt=qcow2 cluster_size=65536 extended_l2=off compression_type=zlib size=134217728 backing_file=TEST_DIR/9-snapshot-v0.qcow2 backing_fmt=qcow2 lazy_refcounts=off refcount_bits=16
 Formatting 'TEST_DIR/10-snapshot-v1.qcow2', fmt=qcow2 cluster_size=65536 extended_l2=off compression_type=zlib size=134217728 backing_file=TEST_DIR/9-snapshot-v1.qcow2 backing_fmt=qcow2 lazy_refcounts=off refcount_bits=16
 {"return": {}}
@@ -69,48 +148,84 @@
 === Create a couple of snapshots using blockdev-snapshot ===
 
 Formatting 'TEST_DIR/11-snapshot-v0.IMGFMT', fmt=IMGFMT size=134217728 backing_file=TEST_DIR/10-snapshot-v0.IMGFMT backing_fmt=IMGFMT
-{ 'execute': 'blockdev-add', 'arguments': { 'driver': 'IMGFMT', 'node-name': 'snap_11', 'backing': null, 'file': { 'driver': 'file', 'filename': 'TEST_DIR/11-snapshot-v0.IMGFMT', 'node-name': 'file_11' } } }
+{ 'execute': 'blockdev-add', 'arguments':
+           { 'driver': 'IMGFMT', 'node-name': 'snap_11', 'backing': null,
+             'file':
+             { 'driver': 'file', 'filename': 'TEST_DIR/11-snapshot-v0.IMGFMT',
+               'node-name': 'file_11' } } }
 {"return": {}}
-{ 'execute': 'blockdev-snapshot', 'arguments': { 'node': 'virtio0', 'overlay':'snap_11' } }
+{ 'execute': 'blockdev-snapshot',
+                      'arguments': { 'node': 'virtio0',
+                                     'overlay':'snap_11' } }
 {"return": {}}
 Formatting 'TEST_DIR/12-snapshot-v0.IMGFMT', fmt=IMGFMT size=134217728 backing_file=TEST_DIR/11-snapshot-v0.IMGFMT backing_fmt=IMGFMT
-{ 'execute': 'blockdev-add', 'arguments': { 'driver': 'IMGFMT', 'node-name': 'snap_12', 'backing': null, 'file': { 'driver': 'file', 'filename': 'TEST_DIR/12-snapshot-v0.IMGFMT', 'node-name': 'file_12' } } }
+{ 'execute': 'blockdev-add', 'arguments':
+           { 'driver': 'IMGFMT', 'node-name': 'snap_12', 'backing': null,
+             'file':
+             { 'driver': 'file', 'filename': 'TEST_DIR/12-snapshot-v0.IMGFMT',
+               'node-name': 'file_12' } } }
 {"return": {}}
-{ 'execute': 'blockdev-snapshot', 'arguments': { 'node': 'virtio0', 'overlay':'snap_12' } }
+{ 'execute': 'blockdev-snapshot',
+                      'arguments': { 'node': 'virtio0',
+                                     'overlay':'snap_12' } }
 {"return": {}}
 
 === Invalid command - cannot create a snapshot using a file BDS ===
 
-{ 'execute': 'blockdev-snapshot', 'arguments': { 'node':'virtio0', 'overlay':'file_12' } }
+{ 'execute': 'blockdev-snapshot',
+                     'arguments': { 'node':'virtio0',
+                                    'overlay':'file_12' }
+                   }
 {"error": {"class": "GenericError", "desc": "The overlay is already in use"}}
 
 === Invalid command - snapshot node used as active layer ===
 
-{ 'execute': 'blockdev-snapshot', 'arguments': { 'node': 'virtio0', 'overlay':'snap_12' } }
+{ 'execute': 'blockdev-snapshot',
+                      'arguments': { 'node': 'virtio0',
+                                     'overlay':'snap_12' } }
 {"error": {"class": "GenericError", "desc": "The overlay is already in use"}}
-{ 'execute': 'blockdev-snapshot', 'arguments': { 'node':'virtio0', 'overlay':'virtio0' } }
+{ 'execute': 'blockdev-snapshot',
+                     'arguments': { 'node':'virtio0',
+                                    'overlay':'virtio0' }
+                   }
 {"error": {"class": "GenericError", "desc": "The overlay is already in use"}}
-{ 'execute': 'blockdev-snapshot', 'arguments': { 'node':'virtio0', 'overlay':'virtio1' } }
+{ 'execute': 'blockdev-snapshot',
+                     'arguments': { 'node':'virtio0',
+                                    'overlay':'virtio1' }
+                   }
 {"error": {"class": "GenericError", "desc": "The overlay is already in use"}}
 
 === Invalid command - snapshot node used as backing hd ===
 
-{ 'execute': 'blockdev-snapshot', 'arguments': { 'node': 'virtio0', 'overlay':'snap_11' } }
+{ 'execute': 'blockdev-snapshot',
+                      'arguments': { 'node': 'virtio0',
+                                     'overlay':'snap_11' } }
 {"error": {"class": "GenericError", "desc": "The overlay is already in use"}}
 
 === Invalid command - snapshot node has a backing image ===
 
 Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=134217728
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
-{ 'execute': 'blockdev-add', 'arguments': { 'driver': 'IMGFMT', 'node-name': 'snap_13', 'file': { 'driver': 'file', 'filename': 'TEST_DIR/t.IMGFMT', 'node-name': 'file_13' } } }
+{ 'execute': 'blockdev-add', 'arguments':
+           { 'driver': 'IMGFMT', 'node-name': 'snap_13',
+             'file':
+             { 'driver': 'file', 'filename': 'TEST_DIR/t.IMGFMT',
+               'node-name': 'file_13' } } }
 {"return": {}}
-{ 'execute': 'blockdev-snapshot', 'arguments': { 'node': 'virtio0', 'overlay':'snap_13' } }
+{ 'execute': 'blockdev-snapshot',
+                      'arguments': { 'node': 'virtio0',
+                                     'overlay':'snap_13' } }
 {"error": {"class": "GenericError", "desc": "The overlay already has a backing image"}}
 
 === Invalid command - The node does not exist ===
 
-{ 'execute': 'blockdev-snapshot', 'arguments': { 'node': 'virtio0', 'overlay':'snap_14' } }
+{ 'execute': 'blockdev-snapshot',
+                      'arguments': { 'node': 'virtio0',
+                                     'overlay':'snap_14' } }
 {"error": {"class": "GenericError", "desc": "Cannot find device=snap_14 nor node_name=snap_14"}}
-{ 'execute': 'blockdev-snapshot', 'arguments': { 'node':'nodevice', 'overlay':'snap_13' } }
+{ 'execute': 'blockdev-snapshot',
+                     'arguments': { 'node':'nodevice',
+                                    'overlay':'snap_13' }
+                   }
 {"error": {"class": "GenericError", "desc": "Cannot find device=nodevice nor node_name=nodevice"}}
 *** done
diff --git a/tests/qemu-iotests/094.out b/tests/qemu-iotests/094.out
index 9b6c57b..97f894c 100644
--- a/tests/qemu-iotests/094.out
+++ b/tests/qemu-iotests/094.out
@@ -3,13 +3,19 @@
 Formatting 'TEST_DIR/source.IMGFMT', fmt=IMGFMT size=67108864
 {'execute': 'qmp_capabilities'}
 {"return": {}}
-{'execute': 'drive-mirror', 'arguments': {'device': 'src', 'target': 'nbd+unix:///?socket=SOCK_DIR/nbd', 'format': 'nbd', 'sync':'full', 'mode':'existing'}}
+{'execute': 'drive-mirror',
+      'arguments': {'device': 'src',
+                    'target': 'nbd+unix:///?socket=SOCK_DIR/nbd',
+                    'format': 'nbd',
+                    'sync':'full',
+                    'mode':'existing'}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "created", "id": "src"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "running", "id": "src"}}
 {"return": {}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "ready", "id": "src"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "BLOCK_JOB_READY", "data": {"device": "src", "len": 67108864, "offset": 67108864, "speed": 0, "type": "mirror"}}
-{'execute': 'block-job-complete', 'arguments': {'device': 'src'}}
+{'execute': 'block-job-complete',
+      'arguments': {'device': 'src'}}
 {"return": {}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "waiting", "id": "src"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "pending", "id": "src"}}
diff --git a/tests/qemu-iotests/095.out b/tests/qemu-iotests/095.out
index e66ced5..8257c5e 100644
--- a/tests/qemu-iotests/095.out
+++ b/tests/qemu-iotests/095.out
@@ -12,7 +12,9 @@
 
 { 'execute': 'qmp_capabilities' }
 {"return": {}}
-{ 'execute': 'block-commit', 'arguments': { 'device': 'test', 'top': 'TEST_DIR/t.IMGFMT.snp1' } }
+{ 'execute': 'block-commit',
+                                 'arguments': { 'device': 'test',
+                                 'top': 'TEST_DIR/t.IMGFMT.snp1' } }
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "created", "id": "test"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "running", "id": "test"}}
 {"return": {}}
diff --git a/tests/qemu-iotests/102 b/tests/qemu-iotests/102
index 2cc3efd..9d747c7 100755
--- a/tests/qemu-iotests/102
+++ b/tests/qemu-iotests/102
@@ -68,7 +68,7 @@
 qemu_comm_method=monitor _launch_qemu -drive if=none,file="$TEST_IMG",id=drv0
 
 # Wait for a prompt to appear (so we know qemu has opened the image)
-_send_qemu_cmd '' '(qemu)'
+_send_qemu_cmd $QEMU_HANDLE '' '(qemu)'
 
 $QEMU_IMG resize --shrink --image-opts \
     "driver=raw,file.driver=file,file.filename=$TEST_IMG,file.locking=off" \
diff --git a/tests/qemu-iotests/102.out b/tests/qemu-iotests/102.out
index cd2fdc7..320ed5a 100644
--- a/tests/qemu-iotests/102.out
+++ b/tests/qemu-iotests/102.out
@@ -16,8 +16,8 @@
 wrote 65536/65536 bytes at offset 0
 64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 QEMU X.Y.Z monitor - type 'help' for more information
-Image resized.
 (qemu)
+Image resized.
 (qemu) qemu-io drv0 map
 64 KiB (0x10000) bytes     allocated at offset 0 bytes (0x0)
 *** done
diff --git a/tests/qemu-iotests/109.out b/tests/qemu-iotests/109.out
index ad739df..6e73406 100644
--- a/tests/qemu-iotests/109.out
+++ b/tests/qemu-iotests/109.out
@@ -6,7 +6,9 @@
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=SIZE
 { 'execute': 'qmp_capabilities' }
 {"return": {}}
-{'execute':'drive-mirror', 'arguments':{ 'device': 'src', 'target': 'TEST_DIR/t.IMGFMT', 'mode': 'existing', 'sync': 'full'}}
+{'execute':'drive-mirror', 'arguments':{
+            'device': 'src', 'target': 'TEST_DIR/t.IMGFMT',
+            'mode': 'existing', 'sync': 'full'}}
 WARNING: Image format was not specified for 'TEST_DIR/t.raw' and probing guessed raw.
          Automatically detecting the format is dangerous for raw images, write operations on block 0 will be restricted.
          Specify the 'raw' format explicitly to remove the restrictions.
@@ -27,7 +29,9 @@
 512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 { 'execute': 'qmp_capabilities' }
 {"return": {}}
-{'execute':'drive-mirror', 'arguments':{ 'device': 'src', 'target': 'TEST_DIR/t.IMGFMT', 'format': 'IMGFMT', 'mode': 'existing', 'sync': 'full'}}
+{'execute':'drive-mirror', 'arguments':{
+            'device': 'src', 'target': 'TEST_DIR/t.IMGFMT', 'format': 'IMGFMT',
+            'mode': 'existing', 'sync': 'full'}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "created", "id": "src"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "running", "id": "src"}}
 {"return": {}}
@@ -51,7 +55,9 @@
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=SIZE
 { 'execute': 'qmp_capabilities' }
 {"return": {}}
-{'execute':'drive-mirror', 'arguments':{ 'device': 'src', 'target': 'TEST_DIR/t.IMGFMT', 'mode': 'existing', 'sync': 'full'}}
+{'execute':'drive-mirror', 'arguments':{
+            'device': 'src', 'target': 'TEST_DIR/t.IMGFMT',
+            'mode': 'existing', 'sync': 'full'}}
 WARNING: Image format was not specified for 'TEST_DIR/t.raw' and probing guessed raw.
          Automatically detecting the format is dangerous for raw images, write operations on block 0 will be restricted.
          Specify the 'raw' format explicitly to remove the restrictions.
@@ -72,7 +78,9 @@
 512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 { 'execute': 'qmp_capabilities' }
 {"return": {}}
-{'execute':'drive-mirror', 'arguments':{ 'device': 'src', 'target': 'TEST_DIR/t.IMGFMT', 'format': 'IMGFMT', 'mode': 'existing', 'sync': 'full'}}
+{'execute':'drive-mirror', 'arguments':{
+            'device': 'src', 'target': 'TEST_DIR/t.IMGFMT', 'format': 'IMGFMT',
+            'mode': 'existing', 'sync': 'full'}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "created", "id": "src"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "running", "id": "src"}}
 {"return": {}}
@@ -96,7 +104,9 @@
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=SIZE
 { 'execute': 'qmp_capabilities' }
 {"return": {}}
-{'execute':'drive-mirror', 'arguments':{ 'device': 'src', 'target': 'TEST_DIR/t.IMGFMT', 'mode': 'existing', 'sync': 'full'}}
+{'execute':'drive-mirror', 'arguments':{
+            'device': 'src', 'target': 'TEST_DIR/t.IMGFMT',
+            'mode': 'existing', 'sync': 'full'}}
 WARNING: Image format was not specified for 'TEST_DIR/t.raw' and probing guessed raw.
          Automatically detecting the format is dangerous for raw images, write operations on block 0 will be restricted.
          Specify the 'raw' format explicitly to remove the restrictions.
@@ -117,7 +127,9 @@
 512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 { 'execute': 'qmp_capabilities' }
 {"return": {}}
-{'execute':'drive-mirror', 'arguments':{ 'device': 'src', 'target': 'TEST_DIR/t.IMGFMT', 'format': 'IMGFMT', 'mode': 'existing', 'sync': 'full'}}
+{'execute':'drive-mirror', 'arguments':{
+            'device': 'src', 'target': 'TEST_DIR/t.IMGFMT', 'format': 'IMGFMT',
+            'mode': 'existing', 'sync': 'full'}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "created", "id": "src"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "running", "id": "src"}}
 {"return": {}}
@@ -141,7 +153,9 @@
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=SIZE
 { 'execute': 'qmp_capabilities' }
 {"return": {}}
-{'execute':'drive-mirror', 'arguments':{ 'device': 'src', 'target': 'TEST_DIR/t.IMGFMT', 'mode': 'existing', 'sync': 'full'}}
+{'execute':'drive-mirror', 'arguments':{
+            'device': 'src', 'target': 'TEST_DIR/t.IMGFMT',
+            'mode': 'existing', 'sync': 'full'}}
 WARNING: Image format was not specified for 'TEST_DIR/t.raw' and probing guessed raw.
          Automatically detecting the format is dangerous for raw images, write operations on block 0 will be restricted.
          Specify the 'raw' format explicitly to remove the restrictions.
@@ -162,7 +176,9 @@
 512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 { 'execute': 'qmp_capabilities' }
 {"return": {}}
-{'execute':'drive-mirror', 'arguments':{ 'device': 'src', 'target': 'TEST_DIR/t.IMGFMT', 'format': 'IMGFMT', 'mode': 'existing', 'sync': 'full'}}
+{'execute':'drive-mirror', 'arguments':{
+            'device': 'src', 'target': 'TEST_DIR/t.IMGFMT', 'format': 'IMGFMT',
+            'mode': 'existing', 'sync': 'full'}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "created", "id": "src"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "running", "id": "src"}}
 {"return": {}}
@@ -186,7 +202,9 @@
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=SIZE
 { 'execute': 'qmp_capabilities' }
 {"return": {}}
-{'execute':'drive-mirror', 'arguments':{ 'device': 'src', 'target': 'TEST_DIR/t.IMGFMT', 'mode': 'existing', 'sync': 'full'}}
+{'execute':'drive-mirror', 'arguments':{
+            'device': 'src', 'target': 'TEST_DIR/t.IMGFMT',
+            'mode': 'existing', 'sync': 'full'}}
 WARNING: Image format was not specified for 'TEST_DIR/t.raw' and probing guessed raw.
          Automatically detecting the format is dangerous for raw images, write operations on block 0 will be restricted.
          Specify the 'raw' format explicitly to remove the restrictions.
@@ -207,7 +225,9 @@
 512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 { 'execute': 'qmp_capabilities' }
 {"return": {}}
-{'execute':'drive-mirror', 'arguments':{ 'device': 'src', 'target': 'TEST_DIR/t.IMGFMT', 'format': 'IMGFMT', 'mode': 'existing', 'sync': 'full'}}
+{'execute':'drive-mirror', 'arguments':{
+            'device': 'src', 'target': 'TEST_DIR/t.IMGFMT', 'format': 'IMGFMT',
+            'mode': 'existing', 'sync': 'full'}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "created", "id": "src"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "running", "id": "src"}}
 {"return": {}}
@@ -231,7 +251,9 @@
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=SIZE
 { 'execute': 'qmp_capabilities' }
 {"return": {}}
-{'execute':'drive-mirror', 'arguments':{ 'device': 'src', 'target': 'TEST_DIR/t.IMGFMT', 'mode': 'existing', 'sync': 'full'}}
+{'execute':'drive-mirror', 'arguments':{
+            'device': 'src', 'target': 'TEST_DIR/t.IMGFMT',
+            'mode': 'existing', 'sync': 'full'}}
 WARNING: Image format was not specified for 'TEST_DIR/t.raw' and probing guessed raw.
          Automatically detecting the format is dangerous for raw images, write operations on block 0 will be restricted.
          Specify the 'raw' format explicitly to remove the restrictions.
@@ -252,7 +274,9 @@
 512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 { 'execute': 'qmp_capabilities' }
 {"return": {}}
-{'execute':'drive-mirror', 'arguments':{ 'device': 'src', 'target': 'TEST_DIR/t.IMGFMT', 'format': 'IMGFMT', 'mode': 'existing', 'sync': 'full'}}
+{'execute':'drive-mirror', 'arguments':{
+            'device': 'src', 'target': 'TEST_DIR/t.IMGFMT', 'format': 'IMGFMT',
+            'mode': 'existing', 'sync': 'full'}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "created", "id": "src"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "running", "id": "src"}}
 {"return": {}}
@@ -275,7 +299,9 @@
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=SIZE
 { 'execute': 'qmp_capabilities' }
 {"return": {}}
-{'execute':'drive-mirror', 'arguments':{ 'device': 'src', 'target': 'TEST_DIR/t.IMGFMT', 'mode': 'existing', 'sync': 'full'}}
+{'execute':'drive-mirror', 'arguments':{
+            'device': 'src', 'target': 'TEST_DIR/t.IMGFMT',
+            'mode': 'existing', 'sync': 'full'}}
 WARNING: Image format was not specified for 'TEST_DIR/t.raw' and probing guessed raw.
          Automatically detecting the format is dangerous for raw images, write operations on block 0 will be restricted.
          Specify the 'raw' format explicitly to remove the restrictions.
@@ -296,7 +322,9 @@
 512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 { 'execute': 'qmp_capabilities' }
 {"return": {}}
-{'execute':'drive-mirror', 'arguments':{ 'device': 'src', 'target': 'TEST_DIR/t.IMGFMT', 'format': 'IMGFMT', 'mode': 'existing', 'sync': 'full'}}
+{'execute':'drive-mirror', 'arguments':{
+            'device': 'src', 'target': 'TEST_DIR/t.IMGFMT', 'format': 'IMGFMT',
+            'mode': 'existing', 'sync': 'full'}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "created", "id": "src"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "running", "id": "src"}}
 {"return": {}}
@@ -319,7 +347,9 @@
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=SIZE
 { 'execute': 'qmp_capabilities' }
 {"return": {}}
-{'execute':'drive-mirror', 'arguments':{ 'device': 'src', 'target': 'TEST_DIR/t.IMGFMT', 'mode': 'existing', 'sync': 'full'}}
+{'execute':'drive-mirror', 'arguments':{
+            'device': 'src', 'target': 'TEST_DIR/t.IMGFMT',
+            'mode': 'existing', 'sync': 'full'}}
 WARNING: Image format was not specified for 'TEST_DIR/t.raw' and probing guessed raw.
          Automatically detecting the format is dangerous for raw images, write operations on block 0 will be restricted.
          Specify the 'raw' format explicitly to remove the restrictions.
@@ -340,7 +370,9 @@
 512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 { 'execute': 'qmp_capabilities' }
 {"return": {}}
-{'execute':'drive-mirror', 'arguments':{ 'device': 'src', 'target': 'TEST_DIR/t.IMGFMT', 'format': 'IMGFMT', 'mode': 'existing', 'sync': 'full'}}
+{'execute':'drive-mirror', 'arguments':{
+            'device': 'src', 'target': 'TEST_DIR/t.IMGFMT', 'format': 'IMGFMT',
+            'mode': 'existing', 'sync': 'full'}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "created", "id": "src"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "running", "id": "src"}}
 {"return": {}}
@@ -363,7 +395,9 @@
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=SIZE
 { 'execute': 'qmp_capabilities' }
 {"return": {}}
-{'execute':'drive-mirror', 'arguments':{ 'device': 'src', 'target': 'TEST_DIR/t.IMGFMT', 'mode': 'existing', 'sync': 'full'}}
+{'execute':'drive-mirror', 'arguments':{
+            'device': 'src', 'target': 'TEST_DIR/t.IMGFMT',
+            'mode': 'existing', 'sync': 'full'}}
 WARNING: Image format was not specified for 'TEST_DIR/t.raw' and probing guessed raw.
          Automatically detecting the format is dangerous for raw images, write operations on block 0 will be restricted.
          Specify the 'raw' format explicitly to remove the restrictions.
@@ -384,7 +418,9 @@
 512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 { 'execute': 'qmp_capabilities' }
 {"return": {}}
-{'execute':'drive-mirror', 'arguments':{ 'device': 'src', 'target': 'TEST_DIR/t.IMGFMT', 'format': 'IMGFMT', 'mode': 'existing', 'sync': 'full'}}
+{'execute':'drive-mirror', 'arguments':{
+            'device': 'src', 'target': 'TEST_DIR/t.IMGFMT', 'format': 'IMGFMT',
+            'mode': 'existing', 'sync': 'full'}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "created", "id": "src"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "running", "id": "src"}}
 {"return": {}}
@@ -407,7 +443,9 @@
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=SIZE
 { 'execute': 'qmp_capabilities' }
 {"return": {}}
-{'execute':'drive-mirror', 'arguments':{ 'device': 'src', 'target': 'TEST_DIR/t.IMGFMT', 'mode': 'existing', 'sync': 'full'}}
+{'execute':'drive-mirror', 'arguments':{
+            'device': 'src', 'target': 'TEST_DIR/t.IMGFMT',
+            'mode': 'existing', 'sync': 'full'}}
 WARNING: Image format was not specified for 'TEST_DIR/t.raw' and probing guessed raw.
          Automatically detecting the format is dangerous for raw images, write operations on block 0 will be restricted.
          Specify the 'raw' format explicitly to remove the restrictions.
@@ -428,7 +466,9 @@
 512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 { 'execute': 'qmp_capabilities' }
 {"return": {}}
-{'execute':'drive-mirror', 'arguments':{ 'device': 'src', 'target': 'TEST_DIR/t.IMGFMT', 'format': 'IMGFMT', 'mode': 'existing', 'sync': 'full'}}
+{'execute':'drive-mirror', 'arguments':{
+            'device': 'src', 'target': 'TEST_DIR/t.IMGFMT', 'format': 'IMGFMT',
+            'mode': 'existing', 'sync': 'full'}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "created", "id": "src"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "running", "id": "src"}}
 {"return": {}}
@@ -451,7 +491,9 @@
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=SIZE
 { 'execute': 'qmp_capabilities' }
 {"return": {}}
-{'execute':'drive-mirror', 'arguments':{ 'device': 'src', 'target': 'TEST_DIR/t.IMGFMT', 'mode': 'existing', 'sync': 'full'}}
+{'execute':'drive-mirror', 'arguments':{
+            'device': 'src', 'target': 'TEST_DIR/t.IMGFMT',
+            'mode': 'existing', 'sync': 'full'}}
 WARNING: Image format was not specified for 'TEST_DIR/t.raw' and probing guessed raw.
          Automatically detecting the format is dangerous for raw images, write operations on block 0 will be restricted.
          Specify the 'raw' format explicitly to remove the restrictions.
@@ -473,7 +515,9 @@
 Images are identical.
 { 'execute': 'qmp_capabilities' }
 {"return": {}}
-{'execute':'drive-mirror', 'arguments':{ 'device': 'src', 'target': 'TEST_DIR/t.IMGFMT', 'format': 'IMGFMT', 'mode': 'existing', 'sync': 'full'}}
+{'execute':'drive-mirror', 'arguments':{
+            'device': 'src', 'target': 'TEST_DIR/t.IMGFMT', 'format': 'IMGFMT',
+            'mode': 'existing', 'sync': 'full'}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "created", "id": "src"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "running", "id": "src"}}
 {"return": {}}
diff --git a/tests/qemu-iotests/117.out b/tests/qemu-iotests/117.out
index bb623dc..735ffd2 100644
--- a/tests/qemu-iotests/117.out
+++ b/tests/qemu-iotests/117.out
@@ -2,11 +2,18 @@
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=65536
 { 'execute': 'qmp_capabilities' }
 {"return": {}}
-{ 'execute': 'blockdev-add', 'arguments': { 'node-name': 'protocol', 'driver': 'file', 'filename': 'TEST_DIR/t.IMGFMT' } }
+{ 'execute': 'blockdev-add',
+       'arguments': { 'node-name': 'protocol',
+                      'driver': 'file',
+                      'filename': 'TEST_DIR/t.IMGFMT' } }
 {"return": {}}
-{ 'execute': 'blockdev-add', 'arguments': { 'node-name': 'format', 'driver': 'IMGFMT', 'file': 'protocol' } }
+{ 'execute': 'blockdev-add',
+       'arguments': { 'node-name': 'format',
+                      'driver': 'IMGFMT',
+                      'file': 'protocol' } }
 {"return": {}}
-{ 'execute': 'human-monitor-command', 'arguments': { 'command-line': 'qemu-io format "write -P 42 0 64k"' } }
+{ 'execute': 'human-monitor-command',
+       'arguments': { 'command-line': 'qemu-io format "write -P 42 0 64k"' } }
 wrote 65536/65536 bytes at offset 0
 64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 {"return": ""}
diff --git a/tests/qemu-iotests/127.out b/tests/qemu-iotests/127.out
index efd6cb3..1685c48 100644
--- a/tests/qemu-iotests/127.out
+++ b/tests/qemu-iotests/127.out
@@ -6,13 +6,21 @@
 42 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 { 'execute': 'qmp_capabilities' }
 {"return": {}}
-{ 'execute': 'drive-mirror', 'arguments': { 'job-id': 'mirror', 'device': 'source', 'target': 'TEST_DIR/t.IMGFMT.overlay1', 'mode': 'existing', 'sync': 'top' } }
+{ 'execute': 'drive-mirror',
+       'arguments': {
+           'job-id': 'mirror',
+           'device': 'source',
+           'target': 'TEST_DIR/t.IMGFMT.overlay1',
+           'mode':   'existing',
+           'sync':   'top'
+       } }
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "created", "id": "mirror"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "running", "id": "mirror"}}
 {"return": {}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "ready", "id": "mirror"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "BLOCK_JOB_READY", "data": {"device": "mirror", "len": 65536, "offset": 65536, "speed": 0, "type": "mirror"}}
-{ 'execute': 'block-job-complete', 'arguments': { 'device': 'mirror' } }
+{ 'execute': 'block-job-complete',
+       'arguments': { 'device': 'mirror' } }
 {"return": {}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "waiting", "id": "mirror"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "pending", "id": "mirror"}}
diff --git a/tests/qemu-iotests/140.out b/tests/qemu-iotests/140.out
index 62d9c3a..312f76d 100644
--- a/tests/qemu-iotests/140.out
+++ b/tests/qemu-iotests/140.out
@@ -4,13 +4,17 @@
 64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 { 'execute': 'qmp_capabilities' }
 {"return": {}}
-{ 'execute': 'nbd-server-start', 'arguments': { 'addr': { 'type': 'unix', 'data': { 'path': 'SOCK_DIR/nbd' }}}}
+{ 'execute': 'nbd-server-start',
+       'arguments': { 'addr': { 'type': 'unix',
+                                'data': { 'path': 'SOCK_DIR/nbd' }}}}
 {"return": {}}
-{ 'execute': 'nbd-server-add', 'arguments': { 'device': 'drv' }}
+{ 'execute': 'nbd-server-add',
+       'arguments': { 'device': 'drv' }}
 {"return": {}}
 read 65536/65536 bytes at offset 0
 64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
-{ 'execute': 'eject', 'arguments': { 'device': 'drv' }}
+{ 'execute': 'eject',
+       'arguments': { 'device': 'drv' }}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "BLOCK_EXPORT_DELETED", "data": {"id": "drv"}}
 qemu-io: can't open device nbd+unix:///drv?socket=SOCK_DIR/nbd: Requested export not available
 server reported: export 'drv' not present
diff --git a/tests/qemu-iotests/141.out b/tests/qemu-iotests/141.out
index 08e0aec..6d8652e 100644
--- a/tests/qemu-iotests/141.out
+++ b/tests/qemu-iotests/141.out
@@ -7,105 +7,173 @@
 
 === Testing drive-backup ===
 
-{'execute': 'blockdev-add', 'arguments': { 'node-name': 'drv0', 'driver': 'IMGFMT', 'file': { 'driver': 'file', 'filename': 'TEST_DIR/t.IMGFMT' }}}
+{'execute': 'blockdev-add',
+          'arguments': {
+              'node-name': 'drv0',
+              'driver': 'IMGFMT',
+              'file': {
+                  'driver': 'file',
+                  'filename': 'TEST_DIR/t.IMGFMT'
+              }}}
 {"return": {}}
-{'execute': 'drive-backup', 'arguments': {'job-id': 'job0', 'device': 'drv0', 'target': 'TEST_DIR/o.IMGFMT', 'format': 'IMGFMT', 'sync': 'none'}}
+{'execute': 'drive-backup',
+'arguments': {'job-id': 'job0',
+'device': 'drv0',
+'target': 'TEST_DIR/o.IMGFMT',
+'format': 'IMGFMT',
+'sync': 'none'}}
 Formatting 'TEST_DIR/o.IMGFMT', fmt=IMGFMT size=1048576 backing_file=TEST_DIR/t.IMGFMT backing_fmt=IMGFMT
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "created", "id": "job0"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "running", "id": "job0"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "paused", "id": "job0"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "running", "id": "job0"}}
-{'execute': 'blockdev-del', 'arguments': {'node-name': 'drv0'}}
+{'execute': 'blockdev-del',
+          'arguments': {'node-name': 'drv0'}}
 {"error": {"class": "GenericError", "desc": "Node 'drv0' is busy: node is used as backing hd of 'NODE_NAME'"}}
-{'execute': 'block-job-cancel', 'arguments': {'device': 'job0'}}
+{'execute': 'block-job-cancel',
+          'arguments': {'device': 'job0'}}
 {"return": {}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "aborting", "id": "job0"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "BLOCK_JOB_CANCELLED", "data": {"device": "job0", "len": 1048576, "offset": 0, "speed": 0, "type": "backup"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "concluded", "id": "job0"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "null", "id": "job0"}}
-{'execute': 'blockdev-del', 'arguments': {'node-name': 'drv0'}}
+{'execute': 'blockdev-del',
+          'arguments': {'node-name': 'drv0'}}
 {"return": {}}
 
 === Testing drive-mirror ===
 
-{'execute': 'blockdev-add', 'arguments': { 'node-name': 'drv0', 'driver': 'IMGFMT', 'file': { 'driver': 'file', 'filename': 'TEST_DIR/t.IMGFMT' }}}
+{'execute': 'blockdev-add',
+          'arguments': {
+              'node-name': 'drv0',
+              'driver': 'IMGFMT',
+              'file': {
+                  'driver': 'file',
+                  'filename': 'TEST_DIR/t.IMGFMT'
+              }}}
 {"return": {}}
-{'execute': 'drive-mirror', 'arguments': {'job-id': 'job0', 'device': 'drv0', 'target': 'TEST_DIR/o.IMGFMT', 'format': 'IMGFMT', 'sync': 'none'}}
+{'execute': 'drive-mirror',
+'arguments': {'job-id': 'job0',
+'device': 'drv0',
+'target': 'TEST_DIR/o.IMGFMT',
+'format': 'IMGFMT',
+'sync': 'none'}}
 Formatting 'TEST_DIR/o.IMGFMT', fmt=IMGFMT size=1048576 backing_file=TEST_DIR/t.IMGFMT backing_fmt=IMGFMT
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "created", "id": "job0"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "running", "id": "job0"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "ready", "id": "job0"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "BLOCK_JOB_READY", "data": {"device": "job0", "len": 0, "offset": 0, "speed": 0, "type": "mirror"}}
-{'execute': 'blockdev-del', 'arguments': {'node-name': 'drv0'}}
+{'execute': 'blockdev-del',
+          'arguments': {'node-name': 'drv0'}}
 {"error": {"class": "GenericError", "desc": "Node 'drv0' is busy: block device is in use by block job: mirror"}}
-{'execute': 'block-job-cancel', 'arguments': {'device': 'job0'}}
+{'execute': 'block-job-cancel',
+          'arguments': {'device': 'job0'}}
 {"return": {}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "waiting", "id": "job0"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "pending", "id": "job0"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "BLOCK_JOB_COMPLETED", "data": {"device": "job0", "len": 0, "offset": 0, "speed": 0, "type": "mirror"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "concluded", "id": "job0"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "null", "id": "job0"}}
-{'execute': 'blockdev-del', 'arguments': {'node-name': 'drv0'}}
+{'execute': 'blockdev-del',
+          'arguments': {'node-name': 'drv0'}}
 {"return": {}}
 
 === Testing active block-commit ===
 
-{'execute': 'blockdev-add', 'arguments': { 'node-name': 'drv0', 'driver': 'IMGFMT', 'file': { 'driver': 'file', 'filename': 'TEST_DIR/t.IMGFMT' }}}
+{'execute': 'blockdev-add',
+          'arguments': {
+              'node-name': 'drv0',
+              'driver': 'IMGFMT',
+              'file': {
+                  'driver': 'file',
+                  'filename': 'TEST_DIR/t.IMGFMT'
+              }}}
 {"return": {}}
-{'execute': 'block-commit', 'arguments': {'job-id': 'job0', 'device': 'drv0'}}
+{'execute': 'block-commit',
+'arguments': {'job-id': 'job0', 'device': 'drv0'}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "created", "id": "job0"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "running", "id": "job0"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "ready", "id": "job0"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "BLOCK_JOB_READY", "data": {"device": "job0", "len": 0, "offset": 0, "speed": 0, "type": "commit"}}
-{'execute': 'blockdev-del', 'arguments': {'node-name': 'drv0'}}
+{'execute': 'blockdev-del',
+          'arguments': {'node-name': 'drv0'}}
 {"error": {"class": "GenericError", "desc": "Node 'drv0' is busy: block device is in use by block job: commit"}}
-{'execute': 'block-job-cancel', 'arguments': {'device': 'job0'}}
+{'execute': 'block-job-cancel',
+          'arguments': {'device': 'job0'}}
 {"return": {}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "waiting", "id": "job0"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "pending", "id": "job0"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "BLOCK_JOB_COMPLETED", "data": {"device": "job0", "len": 0, "offset": 0, "speed": 0, "type": "commit"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "concluded", "id": "job0"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "null", "id": "job0"}}
-{'execute': 'blockdev-del', 'arguments': {'node-name': 'drv0'}}
+{'execute': 'blockdev-del',
+          'arguments': {'node-name': 'drv0'}}
 {"return": {}}
 
 === Testing non-active block-commit ===
 
 wrote 1048576/1048576 bytes at offset 0
 1 MiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
-{'execute': 'blockdev-add', 'arguments': { 'node-name': 'drv0', 'driver': 'IMGFMT', 'file': { 'driver': 'file', 'filename': 'TEST_DIR/t.IMGFMT' }}}
+{'execute': 'blockdev-add',
+          'arguments': {
+              'node-name': 'drv0',
+              'driver': 'IMGFMT',
+              'file': {
+                  'driver': 'file',
+                  'filename': 'TEST_DIR/t.IMGFMT'
+              }}}
 {"return": {}}
-{'execute': 'block-commit', 'arguments': {'job-id': 'job0', 'device': 'drv0', 'top': 'TEST_DIR/m.IMGFMT', 'speed': 1}}
+{'execute': 'block-commit',
+'arguments': {'job-id': 'job0',
+'device': 'drv0',
+'top':    'TEST_DIR/m.IMGFMT',
+'speed':  1}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "created", "id": "job0"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "running", "id": "job0"}}
-{'execute': 'blockdev-del', 'arguments': {'node-name': 'drv0'}}
+{'execute': 'blockdev-del',
+          'arguments': {'node-name': 'drv0'}}
 {"error": {"class": "GenericError", "desc": "Node drv0 is in use"}}
-{'execute': 'block-job-cancel', 'arguments': {'device': 'job0'}}
+{'execute': 'block-job-cancel',
+          'arguments': {'device': 'job0'}}
 {"return": {}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "aborting", "id": "job0"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "BLOCK_JOB_CANCELLED", "data": {"device": "job0", "len": 1048576, "offset": 524288, "speed": 1, "type": "commit"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "concluded", "id": "job0"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "null", "id": "job0"}}
-{'execute': 'blockdev-del', 'arguments': {'node-name': 'drv0'}}
+{'execute': 'blockdev-del',
+          'arguments': {'node-name': 'drv0'}}
 {"return": {}}
 
 === Testing block-stream ===
 
 wrote 1048576/1048576 bytes at offset 0
 1 MiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
-{'execute': 'blockdev-add', 'arguments': { 'node-name': 'drv0', 'driver': 'IMGFMT', 'file': { 'driver': 'file', 'filename': 'TEST_DIR/t.IMGFMT' }}}
+{'execute': 'blockdev-add',
+          'arguments': {
+              'node-name': 'drv0',
+              'driver': 'IMGFMT',
+              'file': {
+                  'driver': 'file',
+                  'filename': 'TEST_DIR/t.IMGFMT'
+              }}}
 {"return": {}}
-{'execute': 'block-stream', 'arguments': {'job-id': 'job0', 'device': 'drv0', 'speed': 1}}
+{'execute': 'block-stream',
+'arguments': {'job-id': 'job0',
+'device': 'drv0',
+'speed': 1}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "created", "id": "job0"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "running", "id": "job0"}}
-{'execute': 'blockdev-del', 'arguments': {'node-name': 'drv0'}}
+{'execute': 'blockdev-del',
+          'arguments': {'node-name': 'drv0'}}
 {"error": {"class": "GenericError", "desc": "Node drv0 is in use"}}
-{'execute': 'block-job-cancel', 'arguments': {'device': 'job0'}}
+{'execute': 'block-job-cancel',
+          'arguments': {'device': 'job0'}}
 {"return": {}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "aborting", "id": "job0"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "BLOCK_JOB_CANCELLED", "data": {"device": "job0", "len": 1048576, "offset": 524288, "speed": 1, "type": "stream"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "concluded", "id": "job0"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "null", "id": "job0"}}
-{'execute': 'blockdev-del', 'arguments': {'node-name': 'drv0'}}
+{'execute': 'blockdev-del',
+          'arguments': {'node-name': 'drv0'}}
 {"return": {}}
 *** done
diff --git a/tests/qemu-iotests/143.out b/tests/qemu-iotests/143.out
index fc9c0a7..9ec5888 100644
--- a/tests/qemu-iotests/143.out
+++ b/tests/qemu-iotests/143.out
@@ -1,7 +1,9 @@
 QA output created by 143
 { 'execute': 'qmp_capabilities' }
 {"return": {}}
-{ 'execute': 'nbd-server-start', 'arguments': { 'addr': { 'type': 'unix', 'data': { 'path': 'SOCK_DIR/nbd' }}}}
+{ 'execute': 'nbd-server-start',
+       'arguments': { 'addr': { 'type': 'unix',
+                                'data': { 'path': 'SOCK_DIR/nbd' }}}}
 {"return": {}}
 qemu-io: can't open device nbd+unix:///no_such_export?socket=SOCK_DIR/nbd: Requested export not available
 server reported: export 'no_such_export' not present
diff --git a/tests/qemu-iotests/144.out b/tests/qemu-iotests/144.out
index 13e0c4f..b3b4812 100644
--- a/tests/qemu-iotests/144.out
+++ b/tests/qemu-iotests/144.out
@@ -8,19 +8,33 @@
 
 { 'execute': 'qmp_capabilities' }
 {"return": {}}
-{ 'execute': 'blockdev-snapshot-sync', 'arguments': { 'device': 'virtio0', 'snapshot-file':'TEST_DIR/tmp.IMGFMT', 'format': 'IMGFMT' } }
+{ 'execute': 'blockdev-snapshot-sync',
+                                'arguments': {
+                                             'device': 'virtio0',
+                                             'snapshot-file':'TEST_DIR/tmp.IMGFMT',
+                                             'format': 'IMGFMT'
+                                             }
+                    }
 Formatting 'TEST_DIR/tmp.qcow2', fmt=qcow2 cluster_size=65536 extended_l2=off compression_type=zlib size=536870912 backing_file=TEST_DIR/t.qcow2 backing_fmt=qcow2 lazy_refcounts=off refcount_bits=16
 {"return": {}}
 
 === Performing block-commit on active layer ===
 
-{ 'execute': 'block-commit', 'arguments': { 'device': 'virtio0' } }
+{ 'execute': 'block-commit',
+                                'arguments': {
+                                                 'device': 'virtio0'
+                                              }
+                    }
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "created", "id": "virtio0"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "running", "id": "virtio0"}}
 {"return": {}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "ready", "id": "virtio0"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "BLOCK_JOB_READY", "data": {"device": "virtio0", "len": 0, "offset": 0, "speed": 0, "type": "commit"}}
-{ 'execute': 'block-job-complete', 'arguments': { 'device': 'virtio0' } }
+{ 'execute': 'block-job-complete',
+                                'arguments': {
+                                                'device': 'virtio0'
+                                              }
+                   }
 {"return": {}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "waiting", "id": "virtio0"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "pending", "id": "virtio0"}}
@@ -30,7 +44,13 @@
 
 === Performing Live Snapshot 2 ===
 
-{ 'execute': 'blockdev-snapshot-sync', 'arguments': { 'device': 'virtio0', 'snapshot-file':'TEST_DIR/tmp2.IMGFMT', 'format': 'IMGFMT' } }
+{ 'execute': 'blockdev-snapshot-sync',
+                                'arguments': {
+                                                'device': 'virtio0',
+                                                'snapshot-file':'TEST_DIR/tmp2.IMGFMT',
+                                                'format': 'IMGFMT'
+                                              }
+                   }
 Formatting 'TEST_DIR/tmp2.qcow2', fmt=qcow2 cluster_size=65536 extended_l2=off compression_type=zlib size=536870912 backing_file=TEST_DIR/t.qcow2 backing_fmt=qcow2 lazy_refcounts=off refcount_bits=16
 {"return": {}}
 *** done
diff --git a/tests/qemu-iotests/153.out b/tests/qemu-iotests/153.out
index fcaa71a..ff8e558 100644
--- a/tests/qemu-iotests/153.out
+++ b/tests/qemu-iotests/153.out
@@ -425,7 +425,8 @@
 { 'execute': 'qmp_capabilities' }
 {"return": {}}
 Adding drive
-{ 'execute': 'human-monitor-command', 'arguments': { 'command-line': 'drive_add 0 if=none,id=d0,file=TEST_DIR/t.IMGFMT' } }
+{ 'execute': 'human-monitor-command',
+       'arguments': { 'command-line': 'drive_add 0 if=none,id=d0,file=TEST_DIR/t.IMGFMT' } }
 {"return": "OKrn"}
 
 _qemu_io_wrapper TEST_DIR/t.qcow2 -c write 0 512
@@ -435,25 +436,30 @@
 
 _qemu_img_wrapper create -f qcow2 -b TEST_DIR/t.qcow2 -F qcow2 TEST_DIR/t.qcow2.overlay
 == Closing an image should unlock it ==
-{ 'execute': 'human-monitor-command', 'arguments': { 'command-line': 'drive_del d0' } }
+{ 'execute': 'human-monitor-command',
+       'arguments': { 'command-line': 'drive_del d0' } }
 {"return": ""}
 
 _qemu_io_wrapper TEST_DIR/t.qcow2 -c write 0 512
 Adding two and closing one
-{ 'execute': 'human-monitor-command', 'arguments': { 'command-line': 'drive_add 0 if=none,id=d0,file=TEST_DIR/t.IMGFMT,readonly=on' } }
+{ 'execute': 'human-monitor-command',
+           'arguments': { 'command-line': 'drive_add 0 if=none,id=d0,file=TEST_DIR/t.IMGFMT,readonly=on' } }
 {"return": "OKrn"}
-{ 'execute': 'human-monitor-command', 'arguments': { 'command-line': 'drive_add 0 if=none,id=d1,file=TEST_DIR/t.IMGFMT,readonly=on' } }
+{ 'execute': 'human-monitor-command',
+           'arguments': { 'command-line': 'drive_add 0 if=none,id=d1,file=TEST_DIR/t.IMGFMT,readonly=on' } }
 {"return": "OKrn"}
 
 _qemu_img_wrapper info TEST_DIR/t.qcow2
-{ 'execute': 'human-monitor-command', 'arguments': { 'command-line': 'drive_del d0' } }
+{ 'execute': 'human-monitor-command',
+       'arguments': { 'command-line': 'drive_del d0' } }
 {"return": ""}
 
 _qemu_io_wrapper TEST_DIR/t.qcow2 -c write 0 512
 qemu-io: can't open device TEST_DIR/t.qcow2: Failed to get "write" lock
 Is another process using the image [TEST_DIR/t.qcow2]?
 Closing the other
-{ 'execute': 'human-monitor-command', 'arguments': { 'command-line': 'drive_del d1' } }
+{ 'execute': 'human-monitor-command',
+       'arguments': { 'command-line': 'drive_del d1' } }
 {"return": ""}
 
 _qemu_io_wrapper TEST_DIR/t.qcow2 -c write 0 512
diff --git a/tests/qemu-iotests/156.out b/tests/qemu-iotests/156.out
index cce167b..4a22f0c 100644
--- a/tests/qemu-iotests/156.out
+++ b/tests/qemu-iotests/156.out
@@ -8,24 +8,37 @@
 { 'execute': 'qmp_capabilities' }
 {"return": {}}
 Formatting 'TEST_DIR/t.IMGFMT.overlay', fmt=IMGFMT size=1048576 backing_file=TEST_DIR/t.IMGFMT backing_fmt=IMGFMT
-{ 'execute': 'blockdev-snapshot-sync', 'arguments': { 'device': 'source', 'snapshot-file': 'TEST_DIR/t.IMGFMT.overlay', 'format': 'IMGFMT', 'mode': 'existing' } }
+{ 'execute': 'blockdev-snapshot-sync',
+       'arguments': { 'device': 'source',
+                      'snapshot-file': 'TEST_DIR/t.IMGFMT.overlay',
+                      'format': 'IMGFMT',
+                      'mode': 'existing' } }
 {"return": {}}
-{ 'execute': 'human-monitor-command', 'arguments': { 'command-line': 'qemu-io source "write -P 3 128k 128k"' } }
+{ 'execute': 'human-monitor-command',
+       'arguments': { 'command-line':
+                      'qemu-io source "write -P 3 128k 128k"' } }
 wrote 131072/131072 bytes at offset 131072
 128 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 {"return": ""}
 Formatting 'TEST_DIR/t.IMGFMT.target.overlay', fmt=IMGFMT size=1048576 backing_file=TEST_DIR/t.IMGFMT.target backing_fmt=IMGFMT
-{ 'execute': 'drive-mirror', 'arguments': { 'device': 'source', 'target': 'TEST_DIR/t.IMGFMT.target.overlay', 'mode': 'existing', 'sync': 'top' } }
+{ 'execute': 'drive-mirror',
+       'arguments': { 'device': 'source',
+                      'target': 'TEST_DIR/t.IMGFMT.target.overlay',
+                      'mode': 'existing',
+                      'sync': 'top' } }
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "created", "id": "source"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "running", "id": "source"}}
 {"return": {}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "ready", "id": "source"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "BLOCK_JOB_READY", "data": {"device": "source", "len": 131072, "offset": 131072, "speed": 0, "type": "mirror"}}
-{ 'execute': 'human-monitor-command', 'arguments': { 'command-line': 'qemu-io source "write -P 4 192k 64k"' } }
+{ 'execute': 'human-monitor-command',
+       'arguments': { 'command-line':
+                      'qemu-io source "write -P 4 192k 64k"' } }
 wrote 65536/65536 bytes at offset 196608
 64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 {"return": ""}
-{ 'execute': 'block-job-complete', 'arguments': { 'device': 'source' } }
+{ 'execute': 'block-job-complete',
+       'arguments': { 'device': 'source' } }
 {"return": {}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "waiting", "id": "source"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "pending", "id": "source"}}
@@ -33,19 +46,27 @@
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "concluded", "id": "source"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "null", "id": "source"}}
 
-{ 'execute': 'human-monitor-command', 'arguments': { 'command-line': 'qemu-io source "read -P 1 0k 64k"' } }
+{ 'execute': 'human-monitor-command',
+       'arguments': { 'command-line':
+                      'qemu-io source "read -P 1 0k 64k"' } }
 read 65536/65536 bytes at offset 0
 64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 {"return": ""}
-{ 'execute': 'human-monitor-command', 'arguments': { 'command-line': 'qemu-io source "read -P 2 64k 64k"' } }
+{ 'execute': 'human-monitor-command',
+       'arguments': { 'command-line':
+                      'qemu-io source "read -P 2 64k 64k"' } }
 read 65536/65536 bytes at offset 65536
 64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 {"return": ""}
-{ 'execute': 'human-monitor-command', 'arguments': { 'command-line': 'qemu-io source "read -P 3 128k 64k"' } }
+{ 'execute': 'human-monitor-command',
+       'arguments': { 'command-line':
+                      'qemu-io source "read -P 3 128k 64k"' } }
 read 65536/65536 bytes at offset 131072
 64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 {"return": ""}
-{ 'execute': 'human-monitor-command', 'arguments': { 'command-line': 'qemu-io source "read -P 4 192k 64k"' } }
+{ 'execute': 'human-monitor-command',
+       'arguments': { 'command-line':
+                      'qemu-io source "read -P 4 192k 64k"' } }
 read 65536/65536 bytes at offset 196608
 64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 {"return": ""}
diff --git a/tests/qemu-iotests/161.out b/tests/qemu-iotests/161.out
index 3d8d89a..6cc285a 100644
--- a/tests/qemu-iotests/161.out
+++ b/tests/qemu-iotests/161.out
@@ -7,18 +7,23 @@
 
 { 'execute': 'qmp_capabilities' }
 {"return": {}}
-{ 'execute': 'human-monitor-command', 'arguments': { 'command-line': 'qemu-io none0 "reopen -o backing.detect-zeroes=on"' } }
+{ 'execute': 'human-monitor-command',
+       'arguments': { 'command-line':
+                      'qemu-io none0 "reopen -o backing.detect-zeroes=on"' } }
 {"return": ""}
 
 *** Stream and then change an option on the backing file
 
 { 'execute': 'qmp_capabilities' }
 {"return": {}}
-{ 'execute': 'block-stream', 'arguments': { 'device': 'none0', 'base': 'TEST_DIR/t.IMGFMT.base' } }
+{ 'execute': 'block-stream',        'arguments': { 'device': 'none0',
+                      'base': 'TEST_DIR/t.IMGFMT.base' } }
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "created", "id": "none0"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "running", "id": "none0"}}
 {"return": {}}
-{ 'execute': 'human-monitor-command', 'arguments': { 'command-line': 'qemu-io none0 "reopen -o backing.detect-zeroes=on"' } }
+{ 'execute': 'human-monitor-command',
+       'arguments': { 'command-line':
+                      'qemu-io none0 "reopen -o backing.detect-zeroes=on"' } }
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "waiting", "id": "none0"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "pending", "id": "none0"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "BLOCK_JOB_COMPLETED", "data": {"device": "none0", "len": 1048576, "offset": 1048576, "speed": 0, "type": "stream"}}
@@ -33,11 +38,14 @@
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1048576 backing_file=TEST_DIR/t.IMGFMT.int backing_fmt=IMGFMT
 { 'execute': 'qmp_capabilities' }
 {"return": {}}
-{ 'execute': 'block-commit', 'arguments': { 'device': 'none0', 'top': 'TEST_DIR/t.IMGFMT.int' } }
+{ 'execute': 'block-commit',        'arguments': { 'device': 'none0',
+                      'top': 'TEST_DIR/t.IMGFMT.int' } }
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "created", "id": "none0"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "running", "id": "none0"}}
 {"return": {}}
-{ 'execute': 'human-monitor-command', 'arguments': { 'command-line': 'qemu-io none0 "reopen -o backing.detect-zeroes=on"' } }
+{ 'execute': 'human-monitor-command',
+       'arguments': { 'command-line':
+                      'qemu-io none0 "reopen -o backing.detect-zeroes=on"' } }
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "waiting", "id": "none0"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "pending", "id": "none0"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "BLOCK_JOB_COMPLETED", "data": {"device": "none0", "len": 1048576, "offset": 1048576, "speed": 0, "type": "commit"}}
diff --git a/tests/qemu-iotests/173.out b/tests/qemu-iotests/173.out
index b5114b5..2d6490d 100644
--- a/tests/qemu-iotests/173.out
+++ b/tests/qemu-iotests/173.out
@@ -6,11 +6,30 @@
 
 { 'execute': 'qmp_capabilities' }
 {"return": {}}
-{ 'arguments': { 'device': 'disk2', 'format': 'IMGFMT', 'mode': 'existing', 'snapshot-file': 'TEST_DIR/image.snp1', 'snapshot-node-name': 'snp1' }, 'execute': 'blockdev-snapshot-sync' }
+{ 'arguments': {
+                        'device': 'disk2',
+                        'format': 'IMGFMT',
+                        'mode': 'existing',
+                        'snapshot-file': 'TEST_DIR/image.snp1',
+                        'snapshot-node-name': 'snp1'
+                     },
+                     'execute': 'blockdev-snapshot-sync'
+                   }
 {"return": {}}
-{ 'arguments': { 'backing-file': 'image.base', 'device': 'disk2', 'image-node-name': 'snp1' }, 'execute': 'change-backing-file' }
+{ 'arguments': {
+                        'backing-file': 'image.base',
+                        'device': 'disk2',
+                        'image-node-name': 'snp1'
+                     },
+                     'execute': 'change-backing-file'
+                   }
 {"return": {}}
-{ 'arguments': { 'base': 'TEST_DIR/image.base', 'device': 'disk2' }, 'execute': 'block-stream' }
+{ 'arguments': {
+                        'base': 'TEST_DIR/image.base',
+                        'device': 'disk2'
+                      },
+                      'execute': 'block-stream'
+                   }
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "created", "id": "disk2"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "running", "id": "disk2"}}
 {"return": {}}
diff --git a/tests/qemu-iotests/182.out b/tests/qemu-iotests/182.out
index ce23340..57f7265 100644
--- a/tests/qemu-iotests/182.out
+++ b/tests/qemu-iotests/182.out
@@ -10,16 +10,42 @@
 
 {'execute': 'qmp_capabilities'}
 {"return": {}}
-{'execute': 'blockdev-add', 'arguments': { 'node-name': 'node0', 'driver': 'file', 'filename': 'TEST_DIR/t.IMGFMT', 'locking': 'on' } }
+{'execute': 'blockdev-add',
+      'arguments': {
+          'node-name': 'node0',
+          'driver': 'file',
+          'filename': 'TEST_DIR/t.IMGFMT',
+          'locking': 'on'
+          } }
 {"return": {}}
-{'execute': 'blockdev-snapshot-sync', 'arguments': { 'node-name': 'node0', 'snapshot-file': 'TEST_DIR/t.IMGFMT.overlay', 'snapshot-node-name': 'node1' } }
+{'execute': 'blockdev-snapshot-sync',
+      'arguments': {
+          'node-name': 'node0',
+          'snapshot-file': 'TEST_DIR/t.IMGFMT.overlay',
+          'snapshot-node-name': 'node1'
+      } }
 Formatting 'TEST_DIR/t.qcow2.overlay', fmt=qcow2 cluster_size=65536 extended_l2=off compression_type=zlib size=197120 backing_file=TEST_DIR/t.qcow2 backing_fmt=file lazy_refcounts=off refcount_bits=16
 {"return": {}}
-{'execute': 'blockdev-add', 'arguments': { 'node-name': 'node1', 'driver': 'file', 'filename': 'TEST_DIR/t.IMGFMT', 'locking': 'on' } }
+{'execute': 'blockdev-add',
+      'arguments': {
+          'node-name': 'node1',
+          'driver': 'file',
+          'filename': 'TEST_DIR/t.IMGFMT',
+          'locking': 'on'
+          } }
 {"return": {}}
-{'execute': 'nbd-server-start', 'arguments': { 'addr': { 'type': 'unix', 'data': { 'path': 'SOCK_DIR/nbd.socket' } } } }
+{'execute': 'nbd-server-start',
+      'arguments': {
+          'addr': {
+              'type': 'unix',
+              'data': {
+                  'path': 'SOCK_DIR/nbd.socket'
+              } } } }
 {"return": {}}
-{'execute': 'nbd-server-add', 'arguments': { 'device': 'node1' } }
+{'execute': 'nbd-server-add',
+      'arguments': {
+          'device': 'node1'
+      } }
 {"return": {}}
 
 === Testing failure to loosen restrictions ===
diff --git a/tests/qemu-iotests/183.out b/tests/qemu-iotests/183.out
index d4be2cb..fd9c2e5 100644
--- a/tests/qemu-iotests/183.out
+++ b/tests/qemu-iotests/183.out
@@ -11,18 +11,23 @@
 
 === Write something on the source ===
 
-{ 'execute': 'human-monitor-command', 'arguments': { 'command-line': 'qemu-io disk "write -P 0x55 0 64k"' } }
+{ 'execute': 'human-monitor-command',
+       'arguments': { 'command-line':
+                      'qemu-io disk "write -P 0x55 0 64k"' } }
 wrote 65536/65536 bytes at offset 0
 64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 {"return": ""}
-{ 'execute': 'human-monitor-command', 'arguments': { 'command-line': 'qemu-io disk "read -P 0x55 0 64k"' } }
+{ 'execute': 'human-monitor-command',
+       'arguments': { 'command-line':
+                      'qemu-io disk "read -P 0x55 0 64k"' } }
 read 65536/65536 bytes at offset 0
 64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 {"return": ""}
 
 === Do block migration to destination ===
 
-{ 'execute': 'migrate', 'arguments': { 'uri': 'unix:SOCK_DIR/migrate', 'blk': true } }
+{ 'execute': 'migrate',
+       'arguments': { 'uri': 'unix:SOCK_DIR/migrate', 'blk': true } }
 {"return": {}}
 { 'execute': 'query-status' }
 {"return": {"status": "postmigrate", "singlestep": false, "running": false}}
@@ -32,11 +37,15 @@
 { 'execute': 'query-status' }
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "RESUME"}
 {"return": {"status": "running", "singlestep": false, "running": true}}
-{ 'execute': 'human-monitor-command', 'arguments': { 'command-line': 'qemu-io disk "read -P 0x55 0 64k"' } }
+{ 'execute': 'human-monitor-command',
+       'arguments': { 'command-line':
+                      'qemu-io disk "read -P 0x55 0 64k"' } }
 read 65536/65536 bytes at offset 0
 64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 {"return": ""}
-{ 'execute': 'human-monitor-command', 'arguments': { 'command-line': 'qemu-io disk "write -P 0x66 1M 64k"' } }
+{ 'execute': 'human-monitor-command',
+       'arguments': { 'command-line':
+                      'qemu-io disk "write -P 0x66 1M 64k"' } }
 wrote 65536/65536 bytes at offset 1048576
 64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 {"return": ""}
diff --git a/tests/qemu-iotests/185.out b/tests/qemu-iotests/185.out
index 339438a..eab55d2 100644
--- a/tests/qemu-iotests/185.out
+++ b/tests/qemu-iotests/185.out
@@ -8,20 +8,34 @@
 
 === Creating backing chain ===
 
-{ 'execute': 'blockdev-snapshot-sync', 'arguments': { 'device': 'disk', 'snapshot-file': 'TEST_DIR/t.IMGFMT.mid', 'format': 'IMGFMT', 'mode': 'absolute-paths' } }
+{ 'execute': 'blockdev-snapshot-sync',
+       'arguments': { 'device': 'disk',
+                      'snapshot-file': 'TEST_DIR/t.IMGFMT.mid',
+                      'format': 'IMGFMT',
+                      'mode': 'absolute-paths' } }
 Formatting 'TEST_DIR/t.qcow2.mid', fmt=qcow2 cluster_size=65536 extended_l2=off compression_type=zlib size=67108864 backing_file=TEST_DIR/t.qcow2.base backing_fmt=qcow2 lazy_refcounts=off refcount_bits=16
 {"return": {}}
-{ 'execute': 'human-monitor-command', 'arguments': { 'command-line': 'qemu-io disk "write 0 4M"' } }
+{ 'execute': 'human-monitor-command',
+       'arguments': { 'command-line':
+                      'qemu-io disk "write 0 4M"' } }
 wrote 4194304/4194304 bytes at offset 0
 4 MiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 {"return": ""}
-{ 'execute': 'blockdev-snapshot-sync', 'arguments': { 'device': 'disk', 'snapshot-file': 'TEST_DIR/t.IMGFMT', 'format': 'IMGFMT', 'mode': 'absolute-paths' } }
+{ 'execute': 'blockdev-snapshot-sync',
+       'arguments': { 'device': 'disk',
+                      'snapshot-file': 'TEST_DIR/t.IMGFMT',
+                      'format': 'IMGFMT',
+                      'mode': 'absolute-paths' } }
 Formatting 'TEST_DIR/t.qcow2', fmt=qcow2 cluster_size=65536 extended_l2=off compression_type=zlib size=67108864 backing_file=TEST_DIR/t.qcow2.mid backing_fmt=qcow2 lazy_refcounts=off refcount_bits=16
 {"return": {}}
 
 === Start commit job and exit qemu ===
 
-{ 'execute': 'block-commit', 'arguments': { 'device': 'disk', 'base':'TEST_DIR/t.IMGFMT.base', 'top': 'TEST_DIR/t.IMGFMT.mid', 'speed': 65536 } }
+{ 'execute': 'block-commit',
+       'arguments': { 'device': 'disk',
+                      'base':'TEST_DIR/t.IMGFMT.base',
+                      'top': 'TEST_DIR/t.IMGFMT.mid',
+                      'speed': 65536 } }
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "created", "id": "disk"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "running", "id": "disk"}}
 {"return": {}}
@@ -34,7 +48,10 @@
 
 { 'execute': 'qmp_capabilities' }
 {"return": {}}
-{ 'execute': 'block-commit', 'arguments': { 'device': 'disk', 'base':'TEST_DIR/t.IMGFMT.base', 'speed': 65536 } }
+{ 'execute': 'block-commit',
+       'arguments': { 'device': 'disk',
+                      'base':'TEST_DIR/t.IMGFMT.base',
+                      'speed': 65536 } }
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "created", "id": "disk"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "running", "id": "disk"}}
 {"return": {}}
@@ -47,7 +64,12 @@
 
 { 'execute': 'qmp_capabilities' }
 {"return": {}}
-{ 'execute': 'drive-mirror', 'arguments': { 'device': 'disk', 'target': 'TEST_DIR/t.IMGFMT.copy', 'format': 'IMGFMT', 'sync': 'full', 'speed': 65536 } }
+{ 'execute': 'drive-mirror',
+       'arguments': { 'device': 'disk',
+                      'target': 'TEST_DIR/t.IMGFMT.copy',
+                      'format': 'IMGFMT',
+                      'sync': 'full',
+                      'speed': 65536 } }
 Formatting 'TEST_DIR/t.qcow2.copy', fmt=qcow2 cluster_size=65536 extended_l2=off compression_type=zlib size=67108864 lazy_refcounts=off refcount_bits=16
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "created", "id": "disk"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "running", "id": "disk"}}
@@ -61,7 +83,12 @@
 
 { 'execute': 'qmp_capabilities' }
 {"return": {}}
-{ 'execute': 'drive-backup', 'arguments': { 'device': 'disk', 'target': 'TEST_DIR/t.IMGFMT.copy', 'format': 'IMGFMT', 'sync': 'full', 'speed': 65536 } }
+{ 'execute': 'drive-backup',
+       'arguments': { 'device': 'disk',
+                      'target': 'TEST_DIR/t.IMGFMT.copy',
+                      'format': 'IMGFMT',
+                      'sync': 'full',
+                      'speed': 65536 } }
 Formatting 'TEST_DIR/t.qcow2.copy', fmt=qcow2 cluster_size=65536 extended_l2=off compression_type=zlib size=67108864 lazy_refcounts=off refcount_bits=16
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "created", "id": "disk"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "running", "id": "disk"}}
@@ -77,7 +104,9 @@
 
 { 'execute': 'qmp_capabilities' }
 {"return": {}}
-{ 'execute': 'block-stream', 'arguments': { 'device': 'disk', 'speed': 65536 } }
+{ 'execute': 'block-stream',
+       'arguments': { 'device': 'disk',
+                      'speed': 65536 } }
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "created", "id": "disk"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "running", "id": "disk"}}
 {"return": {}}
diff --git a/tests/qemu-iotests/191.out b/tests/qemu-iotests/191.out
index 11aaf3b..022021e 100644
--- a/tests/qemu-iotests/191.out
+++ b/tests/qemu-iotests/191.out
@@ -16,7 +16,11 @@
 
 === Perform commit job ===
 
-{ 'execute': 'block-commit', 'arguments': { 'job-id': 'commit0', 'device': 'top', 'base':'TEST_DIR/t.IMGFMT.base', 'top': 'TEST_DIR/t.IMGFMT.mid' } }
+{ 'execute': 'block-commit',
+       'arguments': { 'job-id': 'commit0',
+                      'device': 'top',
+                      'base':'TEST_DIR/t.IMGFMT.base',
+                      'top': 'TEST_DIR/t.IMGFMT.mid' } }
 {
     "timestamp": {
         "seconds":  TIMESTAMP,
@@ -427,7 +431,11 @@
 
 === Perform commit job ===
 
-{ 'execute': 'block-commit', 'arguments': { 'job-id': 'commit0', 'device': 'top', 'base':'TEST_DIR/t.IMGFMT.base', 'top': 'TEST_DIR/t.IMGFMT.mid' } }
+{ 'execute': 'block-commit',
+       'arguments': { 'job-id': 'commit0',
+                      'device': 'top',
+                      'base':'TEST_DIR/t.IMGFMT.base',
+                      'top': 'TEST_DIR/t.IMGFMT.mid' } }
 {
     "timestamp": {
         "seconds":  TIMESTAMP,
diff --git a/tests/qemu-iotests/223.out b/tests/qemu-iotests/223.out
index f6eac23..bbc8528 100644
--- a/tests/qemu-iotests/223.out
+++ b/tests/qemu-iotests/223.out
@@ -26,31 +26,48 @@
 
 {"execute":"qmp_capabilities"}
 {"return": {}}
-{"execute":"blockdev-add", "arguments":{"driver":"IMGFMT", "node-name":"n", "file":{"driver":"file", "filename":"TEST_DIR/t.IMGFMT"}}}
+{"execute":"blockdev-add",
+  "arguments":{"driver":"IMGFMT", "node-name":"n",
+    "file":{"driver":"file", "filename":"TEST_DIR/t.IMGFMT"}}}
 {"return": {}}
-{"execute":"block-dirty-bitmap-disable", "arguments":{"node":"n", "name":"b"}}
+{"execute":"block-dirty-bitmap-disable",
+  "arguments":{"node":"n", "name":"b"}}
 {"return": {}}
 
 === Set up NBD with normal access ===
 
-{"execute":"nbd-server-add", "arguments":{"device":"n"}}
+{"execute":"nbd-server-add",
+  "arguments":{"device":"n"}}
 {"error": {"class": "GenericError", "desc": "NBD server not running"}}
-{"execute":"nbd-server-start", "arguments":{"addr":{"type":"unix", "data":{"path":"SOCK_DIR/nbd"}}}}
+{"execute":"nbd-server-start",
+  "arguments":{"addr":{"type":"unix",
+    "data":{"path":"SOCK_DIR/nbd"}}}}
 {"return": {}}
-{"execute":"nbd-server-start", "arguments":{"addr":{"type":"unix", "data":{"path":"SOCK_DIR/nbd1"}}}}
+{"execute":"nbd-server-start",
+  "arguments":{"addr":{"type":"unix",
+    "data":{"path":"SOCK_DIR/nbd1"}}}}
 {"error": {"class": "GenericError", "desc": "NBD server already running"}}
 exports available: 0
-{"execute":"nbd-server-add", "arguments":{"device":"n", "bitmap":"b"}}
+{"execute":"nbd-server-add",
+  "arguments":{"device":"n", "bitmap":"b"}}
 {"return": {}}
-{"execute":"nbd-server-add", "arguments":{"device":"nosuch"}}
+{"execute":"nbd-server-add",
+  "arguments":{"device":"nosuch"}}
 {"error": {"class": "GenericError", "desc": "Cannot find device=nosuch nor node_name=nosuch"}}
-{"execute":"nbd-server-add", "arguments":{"device":"n"}}
+{"execute":"nbd-server-add",
+  "arguments":{"device":"n"}}
 {"error": {"class": "GenericError", "desc": "Block export id 'n' is already in use"}}
-{"execute":"nbd-server-add", "arguments":{"device":"n", "name":"n2", "bitmap":"b2"}}
+{"execute":"nbd-server-add",
+  "arguments":{"device":"n", "name":"n2",
+  "bitmap":"b2"}}
 {"error": {"class": "GenericError", "desc": "Enabled bitmap 'b2' incompatible with readonly export"}}
-{"execute":"nbd-server-add", "arguments":{"device":"n", "name":"n2", "bitmap":"b3"}}
+{"execute":"nbd-server-add",
+  "arguments":{"device":"n", "name":"n2",
+  "bitmap":"b3"}}
 {"error": {"class": "GenericError", "desc": "Bitmap 'b3' is not found"}}
-{"execute":"nbd-server-add", "arguments":{"device":"n", "name":"n2", "writable":true, "description":"some text", "bitmap":"b2"}}
+{"execute":"nbd-server-add",
+  "arguments":{"device":"n", "name":"n2", "writable":true,
+  "description":"some text", "bitmap":"b2"}}
 {"return": {}}
 exports available: 2
  export: 'n'
@@ -99,12 +116,15 @@
 
 === End qemu NBD server ===
 
-{"execute":"nbd-server-remove", "arguments":{"name":"n"}}
+{"execute":"nbd-server-remove",
+  "arguments":{"name":"n"}}
 {"return": {}}
-{"execute":"nbd-server-remove", "arguments":{"name":"n2"}}
+{"execute":"nbd-server-remove",
+  "arguments":{"name":"n2"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "BLOCK_EXPORT_DELETED", "data": {"id": "n"}}
 {"return": {}}
-{"execute":"nbd-server-remove", "arguments":{"name":"n2"}}
+{"execute":"nbd-server-remove",
+  "arguments":{"name":"n2"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "BLOCK_EXPORT_DELETED", "data": {"id": "n2"}}
 {"error": {"class": "GenericError", "desc": "Export 'n2' is not found"}}
 {"execute":"nbd-server-stop"}
@@ -114,26 +134,41 @@
 
 === Set up NBD with iothread access ===
 
-{"execute":"x-blockdev-set-iothread", "arguments":{"node-name":"n", "iothread":"io0"}}
+{"execute":"x-blockdev-set-iothread",
+  "arguments":{"node-name":"n", "iothread":"io0"}}
 {"return": {}}
-{"execute":"nbd-server-add", "arguments":{"device":"n"}}
+{"execute":"nbd-server-add",
+  "arguments":{"device":"n"}}
 {"error": {"class": "GenericError", "desc": "NBD server not running"}}
-{"execute":"nbd-server-start", "arguments":{"addr":{"type":"unix", "data":{"path":"SOCK_DIR/nbd"}}}}
+{"execute":"nbd-server-start",
+  "arguments":{"addr":{"type":"unix",
+    "data":{"path":"SOCK_DIR/nbd"}}}}
 {"return": {}}
-{"execute":"nbd-server-start", "arguments":{"addr":{"type":"unix", "data":{"path":"SOCK_DIR/nbd1"}}}}
+{"execute":"nbd-server-start",
+  "arguments":{"addr":{"type":"unix",
+    "data":{"path":"SOCK_DIR/nbd1"}}}}
 {"error": {"class": "GenericError", "desc": "NBD server already running"}}
 exports available: 0
-{"execute":"nbd-server-add", "arguments":{"device":"n", "bitmap":"b"}}
+{"execute":"nbd-server-add",
+  "arguments":{"device":"n", "bitmap":"b"}}
 {"return": {}}
-{"execute":"nbd-server-add", "arguments":{"device":"nosuch"}}
+{"execute":"nbd-server-add",
+  "arguments":{"device":"nosuch"}}
 {"error": {"class": "GenericError", "desc": "Cannot find device=nosuch nor node_name=nosuch"}}
-{"execute":"nbd-server-add", "arguments":{"device":"n"}}
+{"execute":"nbd-server-add",
+  "arguments":{"device":"n"}}
 {"error": {"class": "GenericError", "desc": "Block export id 'n' is already in use"}}
-{"execute":"nbd-server-add", "arguments":{"device":"n", "name":"n2", "bitmap":"b2"}}
+{"execute":"nbd-server-add",
+  "arguments":{"device":"n", "name":"n2",
+  "bitmap":"b2"}}
 {"error": {"class": "GenericError", "desc": "Enabled bitmap 'b2' incompatible with readonly export"}}
-{"execute":"nbd-server-add", "arguments":{"device":"n", "name":"n2", "bitmap":"b3"}}
+{"execute":"nbd-server-add",
+  "arguments":{"device":"n", "name":"n2",
+  "bitmap":"b3"}}
 {"error": {"class": "GenericError", "desc": "Bitmap 'b3' is not found"}}
-{"execute":"nbd-server-add", "arguments":{"device":"n", "name":"n2", "writable":true, "description":"some text", "bitmap":"b2"}}
+{"execute":"nbd-server-add",
+  "arguments":{"device":"n", "name":"n2", "writable":true,
+  "description":"some text", "bitmap":"b2"}}
 {"return": {}}
 exports available: 2
  export: 'n'
@@ -182,12 +217,15 @@
 
 === End qemu NBD server ===
 
-{"execute":"nbd-server-remove", "arguments":{"name":"n"}}
+{"execute":"nbd-server-remove",
+  "arguments":{"name":"n"}}
 {"return": {}}
-{"execute":"nbd-server-remove", "arguments":{"name":"n2"}}
+{"execute":"nbd-server-remove",
+  "arguments":{"name":"n2"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "BLOCK_EXPORT_DELETED", "data": {"id": "n"}}
 {"return": {}}
-{"execute":"nbd-server-remove", "arguments":{"name":"n2"}}
+{"execute":"nbd-server-remove",
+  "arguments":{"name":"n2"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "BLOCK_EXPORT_DELETED", "data": {"id": "n2"}}
 {"error": {"class": "GenericError", "desc": "Export 'n2' is not found"}}
 {"execute":"nbd-server-stop"}
diff --git a/tests/qemu-iotests/229.out b/tests/qemu-iotests/229.out
index 7eed393..7d2bfbf 100644
--- a/tests/qemu-iotests/229.out
+++ b/tests/qemu-iotests/229.out
@@ -8,7 +8,14 @@
 
 === Starting drive-mirror, causing error & stop  ===
 
-{'execute': 'drive-mirror', 'arguments': {'device': 'testdisk', 'format': 'IMGFMT', 'target': 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.IMGFMT.dest', 'sync': 'full', 'mode': 'existing', 'on-source-error': 'stop', 'on-target-error': 'stop' }}
+{'execute': 'drive-mirror',
+                 'arguments': {'device': 'testdisk',
+                               'format': 'IMGFMT',
+                               'target': 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.IMGFMT.dest',
+                               'sync':   'full',
+                               'mode':   'existing',
+                               'on-source-error': 'stop',
+                               'on-target-error': 'stop' }}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "created", "id": "testdisk"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "running", "id": "testdisk"}}
 {"return": {}}
@@ -17,7 +24,9 @@
 
 === Force cancel job paused in error state  ===
 
-{'execute': 'block-job-cancel', 'arguments': { 'device': 'testdisk', 'force': true}}
+{'execute': 'block-job-cancel',
+                 'arguments': { 'device': 'testdisk',
+                                'force': true}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "running", "id": "testdisk"}}
 {"return": {}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "aborting", "id": "testdisk"}}
diff --git a/tests/qemu-iotests/249.out b/tests/qemu-iotests/249.out
index 85acda4..92ec81d 100644
--- a/tests/qemu-iotests/249.out
+++ b/tests/qemu-iotests/249.out
@@ -7,24 +7,29 @@
 
 === Send a write command to a drive opened in read-only mode (1)
 
-{ 'execute': 'human-monitor-command', 'arguments': {'command-line': 'qemu-io none0 "aio_write 0 2k"'}}
+{ 'execute': 'human-monitor-command',
+       'arguments': {'command-line': 'qemu-io none0 "aio_write 0 2k"'}}
 {"return": "Block node is read-onlyrn"}
 
 === Run block-commit on base using an invalid filter node name
 
-{ 'execute': 'block-commit', 'arguments': {'job-id': 'job0', 'device': 'none1', 'top-node': 'int', 'filter-node-name': '1234'}}
+{ 'execute': 'block-commit',
+       'arguments': {'job-id': 'job0', 'device': 'none1', 'top-node': 'int',
+                     'filter-node-name': '1234'}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "created", "id": "job0"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "null", "id": "job0"}}
 {"error": {"class": "GenericError", "desc": "Invalid node name"}}
 
 === Send a write command to a drive opened in read-only mode (2)
 
-{ 'execute': 'human-monitor-command', 'arguments': {'command-line': 'qemu-io none0 "aio_write 0 2k"'}}
+{ 'execute': 'human-monitor-command',
+       'arguments': {'command-line': 'qemu-io none0 "aio_write 0 2k"'}}
 {"return": "Block node is read-onlyrn"}
 
 === Run block-commit on base using the default filter node name
 
-{ 'execute': 'block-commit', 'arguments': {'job-id': 'job0', 'device': 'none1', 'top-node': 'int'}}
+{ 'execute': 'block-commit',
+       'arguments': {'job-id': 'job0', 'device': 'none1', 'top-node': 'int'}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "created", "id": "job0"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "running", "id": "job0"}}
 {"return": {}}
@@ -36,6 +41,7 @@
 
 === Send a write command to a drive opened in read-only mode (3)
 
-{ 'execute': 'human-monitor-command', 'arguments': {'command-line': 'qemu-io none0 "aio_write 0 2k"'}}
+{ 'execute': 'human-monitor-command',
+       'arguments': {'command-line': 'qemu-io none0 "aio_write 0 2k"'}}
 {"return": "Block node is read-onlyrn"}
 *** done
diff --git a/tests/qemu-iotests/298 b/tests/qemu-iotests/298
new file mode 100644
index 0000000..d535946
--- /dev/null
+++ b/tests/qemu-iotests/298
@@ -0,0 +1,186 @@
+#!/usr/bin/env python3
+#
+# Test for preallocate filter
+#
+# Copyright (c) 2020 Virtuozzo International GmbH.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+#
+
+import os
+import iotests
+
+MiB = 1024 * 1024
+disk = os.path.join(iotests.test_dir, 'disk')
+overlay = os.path.join(iotests.test_dir, 'overlay')
+refdisk = os.path.join(iotests.test_dir, 'refdisk')
+drive_opts = f'node-name=disk,driver={iotests.imgfmt},' \
+    f'file.node-name=filter,file.driver=preallocate,' \
+    f'file.file.node-name=file,file.file.filename={disk}'
+
+
+class TestPreallocateBase(iotests.QMPTestCase):
+    def setUp(self):
+        iotests.qemu_img_create('-f', iotests.imgfmt, disk, str(10 * MiB))
+
+    def tearDown(self):
+        try:
+            self.check_small()
+            check = iotests.qemu_img_check(disk)
+            self.assertFalse('leaks' in check)
+            self.assertFalse('corruptions' in check)
+            self.assertEqual(check['check-errors'], 0)
+        finally:
+            os.remove(disk)
+
+    def check_big(self):
+        self.assertTrue(os.path.getsize(disk) > 100 * MiB)
+
+    def check_small(self):
+        self.assertTrue(os.path.getsize(disk) < 10 * MiB)
+
+
+class TestQemuImg(TestPreallocateBase):
+    def test_qemu_img(self):
+        p = iotests.QemuIoInteractive('--image-opts', drive_opts)
+
+        p.cmd('write 0 1M')
+        p.cmd('flush')
+
+        self.check_big()
+
+        p.close()
+
+
+class TestPreallocateFilter(TestPreallocateBase):
+    def setUp(self):
+        super().setUp()
+        self.vm = iotests.VM().add_drive(path=None, opts=drive_opts)
+        self.vm.launch()
+
+    def tearDown(self):
+        self.vm.shutdown()
+        super().tearDown()
+
+    def test_prealloc(self):
+        self.vm.hmp_qemu_io('drive0', 'write 0 1M')
+        self.check_big()
+
+    def test_external_snapshot(self):
+        self.test_prealloc()
+
+        result = self.vm.qmp('blockdev-snapshot-sync', node_name='disk',
+                             snapshot_file=overlay,
+                             snapshot_node_name='overlay')
+        self.assert_qmp(result, 'return', {})
+
+        # on reopen to  r-o base preallocation should be dropped
+        self.check_small()
+
+        self.vm.hmp_qemu_io('drive0', 'write 1M 1M')
+
+        result = self.vm.qmp('block-commit', device='overlay')
+        self.assert_qmp(result, 'return', {})
+        self.complete_and_wait()
+
+        # commit of new megabyte should trigger preallocation
+        self.check_big()
+
+    def test_reopen_opts(self):
+        result = self.vm.qmp('x-blockdev-reopen', **{
+            'node-name': 'disk',
+            'driver': iotests.imgfmt,
+            'file': {
+                'node-name': 'filter',
+                'driver': 'preallocate',
+                'prealloc-size': 20 * MiB,
+                'prealloc-align': 5 * MiB,
+                'file': {
+                    'node-name': 'file',
+                    'driver': 'file',
+                    'filename': disk
+                }
+            }
+        })
+        self.assert_qmp(result, 'return', {})
+
+        self.vm.hmp_qemu_io('drive0', 'write 0 1M')
+        self.assertTrue(os.path.getsize(disk) == 25 * MiB)
+
+
+class TestTruncate(iotests.QMPTestCase):
+    def setUp(self):
+        iotests.qemu_img_create('-f', iotests.imgfmt, disk, str(10 * MiB))
+        iotests.qemu_img_create('-f', iotests.imgfmt, refdisk, str(10 * MiB))
+
+    def tearDown(self):
+        os.remove(disk)
+        os.remove(refdisk)
+
+    def do_test(self, prealloc_mode, new_size):
+        ret = iotests.qemu_io_silent('--image-opts', '-c', 'write 0 10M', '-c',
+                                     f'truncate -m {prealloc_mode} {new_size}',
+                                     drive_opts)
+        self.assertEqual(ret, 0)
+
+        ret = iotests.qemu_io_silent('-f', iotests.imgfmt, '-c', 'write 0 10M',
+                                     '-c',
+                                     f'truncate -m {prealloc_mode} {new_size}',
+                                     refdisk)
+        self.assertEqual(ret, 0)
+
+        stat = os.stat(disk)
+        refstat = os.stat(refdisk)
+
+        # Probably we'll want preallocate filter to keep align to cluster when
+        # shrink preallocation, so, ignore small differece
+        self.assertLess(abs(stat.st_size - refstat.st_size), 64 * 1024)
+
+        # Preallocate filter may leak some internal clusters (for example, if
+        # guest write far over EOF, skipping some clusters - they will remain
+        # fallocated, preallocate filter don't care about such leaks, it drops
+        # only trailing preallocation.
+        self.assertLess(abs(stat.st_blocks - refstat.st_blocks) * 512,
+                        1024 * 1024)
+
+    def test_real_shrink(self):
+        self.do_test('off', '5M')
+
+    def test_truncate_inside_preallocated_area__falloc(self):
+        self.do_test('falloc', '50M')
+
+    def test_truncate_inside_preallocated_area__metadata(self):
+        self.do_test('metadata', '50M')
+
+    def test_truncate_inside_preallocated_area__full(self):
+        self.do_test('full', '50M')
+
+    def test_truncate_inside_preallocated_area__off(self):
+        self.do_test('off', '50M')
+
+    def test_truncate_over_preallocated_area__falloc(self):
+        self.do_test('falloc', '150M')
+
+    def test_truncate_over_preallocated_area__metadata(self):
+        self.do_test('metadata', '150M')
+
+    def test_truncate_over_preallocated_area__full(self):
+        self.do_test('full', '150M')
+
+    def test_truncate_over_preallocated_area__off(self):
+        self.do_test('off', '150M')
+
+
+if __name__ == '__main__':
+    iotests.main(supported_fmts=['qcow2'], required_fmts=['preallocate'])
diff --git a/tests/qemu-iotests/298.out b/tests/qemu-iotests/298.out
new file mode 100644
index 0000000..fa16b5c
--- /dev/null
+++ b/tests/qemu-iotests/298.out
@@ -0,0 +1,5 @@
+.............
+----------------------------------------------------------------------
+Ran 13 tests
+
+OK
diff --git a/tests/qemu-iotests/308.out b/tests/qemu-iotests/308.out
index b93acee..466e7e0 100644
--- a/tests/qemu-iotests/308.out
+++ b/tests/qemu-iotests/308.out
@@ -5,42 +5,91 @@
 64 MiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 {'execute': 'qmp_capabilities'}
 {"return": {}}
-{'execute': 'blockdev-add', 'arguments': { 'driver': 'file', 'node-name': 'node-protocol', 'filename': 'TEST_DIR/t.IMGFMT' } }
+{'execute': 'blockdev-add',
+      'arguments': {
+          'driver': 'file',
+          'node-name': 'node-protocol',
+          'filename': 'TEST_DIR/t.IMGFMT'
+      } }
 {"return": {}}
-{'execute': 'blockdev-add', 'arguments': { 'driver': 'IMGFMT', 'node-name': 'node-format', 'file': 'node-protocol' } }
+{'execute': 'blockdev-add',
+      'arguments': {
+          'driver': 'IMGFMT',
+          'node-name': 'node-format',
+          'file': 'node-protocol'
+      } }
 {"return": {}}
 
 === Mountpoint not present ===
-{'execute': 'block-export-add', 'arguments': { 'type': 'fuse', 'id': 'export-err', 'node-name': 'node-format', 'mountpoint': 'TEST_DIR/t.IMGFMT.fuse' } }
+{'execute': 'block-export-add',
+          'arguments': {
+              'type': 'fuse',
+              'id': 'export-err',
+              'node-name': 'node-format',
+              'mountpoint': 'TEST_DIR/t.IMGFMT.fuse'
+          } }
 {"error": {"class": "GenericError", "desc": "Failed to stat 'TEST_DIR/t.IMGFMT.fuse': No such file or directory"}}
 
 === Mountpoint is a directory ===
-{'execute': 'block-export-add', 'arguments': { 'type': 'fuse', 'id': 'export-err', 'node-name': 'node-format', 'mountpoint': 'TEST_DIR/t.IMGFMT.fuse' } }
+{'execute': 'block-export-add',
+          'arguments': {
+              'type': 'fuse',
+              'id': 'export-err',
+              'node-name': 'node-format',
+              'mountpoint': 'TEST_DIR/t.IMGFMT.fuse'
+          } }
 {"error": {"class": "GenericError", "desc": "'TEST_DIR/t.IMGFMT.fuse' is not a regular file"}}
 
 === Mountpoint is a regular file ===
-{'execute': 'block-export-add', 'arguments': { 'type': 'fuse', 'id': 'export-mp', 'node-name': 'node-format', 'mountpoint': 'TEST_DIR/t.IMGFMT.fuse' } }
+{'execute': 'block-export-add',
+          'arguments': {
+              'type': 'fuse',
+              'id': 'export-mp',
+              'node-name': 'node-format',
+              'mountpoint': 'TEST_DIR/t.IMGFMT.fuse'
+          } }
 {"return": {}}
 Images are identical.
 
 === Mount over existing file ===
-{'execute': 'block-export-add', 'arguments': { 'type': 'fuse', 'id': 'export-img', 'node-name': 'node-format', 'mountpoint': 'TEST_DIR/t.IMGFMT' } }
+{'execute': 'block-export-add',
+          'arguments': {
+              'type': 'fuse',
+              'id': 'export-img',
+              'node-name': 'node-format',
+              'mountpoint': 'TEST_DIR/t.IMGFMT'
+          } }
 {"return": {}}
 Images are identical.
 
 === Double export ===
-{'execute': 'block-export-add', 'arguments': { 'type': 'fuse', 'id': 'export-err', 'node-name': 'node-format', 'mountpoint': 'TEST_DIR/t.IMGFMT.fuse' } }
+{'execute': 'block-export-add',
+          'arguments': {
+              'type': 'fuse',
+              'id': 'export-err',
+              'node-name': 'node-format',
+              'mountpoint': 'TEST_DIR/t.IMGFMT.fuse'
+          } }
 {"error": {"class": "GenericError", "desc": "There already is a FUSE export on 'TEST_DIR/t.IMGFMT.fuse'"}}
 
 === Remove export ===
 virtual size: 64 MiB (67108864 bytes)
-{'execute': 'block-export-del', 'arguments': { 'id': 'export-mp' } }
+{'execute': 'block-export-del',
+          'arguments': {
+              'id': 'export-mp'
+          } }
 {"return": {}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "BLOCK_EXPORT_DELETED", "data": {"id": "export-mp"}}
 virtual size: 0 B (0 bytes)
 
 === Writable export ===
-{'execute': 'block-export-add', 'arguments': { 'type': 'fuse', 'id': 'export-mp', 'node-name': 'node-format', 'mountpoint': 'TEST_DIR/t.IMGFMT.fuse', 'writable': true } }
+{'execute': 'block-export-add',
+          'arguments': {
+              'type': 'fuse',
+              'id': 'export-mp',
+              'node-name': 'node-format',
+              'mountpoint': 'TEST_DIR/t.IMGFMT.fuse', 'writable': true
+          } }
 {"return": {}}
 write failed: Permission denied
 wrote 65536/65536 bytes at offset 1048576
@@ -49,15 +98,30 @@
 64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 
 === Resizing exports ===
-{'execute': 'block-export-del', 'arguments': { 'id': 'export-mp' } }
+{'execute': 'block-export-del',
+          'arguments': {
+              'id': 'export-mp'
+          } }
 {"return": {}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "BLOCK_EXPORT_DELETED", "data": {"id": "export-mp"}}
-{'execute': 'block-export-del', 'arguments': { 'id': 'export-img' } }
+{'execute': 'block-export-del',
+          'arguments': {
+              'id': 'export-img'
+          } }
 {"return": {}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "BLOCK_EXPORT_DELETED", "data": {"id": "export-img"}}
-{'execute': 'blockdev-del', 'arguments': { 'node-name': 'node-format' } }
+{'execute': 'blockdev-del',
+      'arguments': {
+          'node-name': 'node-format'
+      } }
 {"return": {}}
-{'execute': 'block-export-add', 'arguments': { 'type': 'fuse', 'id': 'export-mp', 'node-name': 'node-protocol', 'mountpoint': 'TEST_DIR/t.IMGFMT.fuse', 'writable': true } }
+{'execute': 'block-export-add',
+          'arguments': {
+              'type': 'fuse',
+              'id': 'export-mp',
+              'node-name': 'node-protocol',
+              'mountpoint': 'TEST_DIR/t.IMGFMT.fuse', 'writable': true
+          } }
 {"return": {}}
 
 --- Try growing non-growable export ---
@@ -72,10 +136,19 @@
 OK: Disk usage grew with fallocate
 
 --- Try growing growable export ---
-{'execute': 'block-export-del', 'arguments': { 'id': 'export-mp' } }
+{'execute': 'block-export-del',
+          'arguments': {
+              'id': 'export-mp'
+          } }
 {"return": {}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "BLOCK_EXPORT_DELETED", "data": {"id": "export-mp"}}
-{'execute': 'block-export-add', 'arguments': { 'type': 'fuse', 'id': 'export-mp', 'node-name': 'node-protocol', 'mountpoint': 'TEST_DIR/t.IMGFMT.fuse', 'writable': true, 'growable': true } }
+{'execute': 'block-export-add',
+          'arguments': {
+              'type': 'fuse',
+              'id': 'export-mp',
+              'node-name': 'node-protocol',
+              'mountpoint': 'TEST_DIR/t.IMGFMT.fuse', 'writable': true, 'growable': true
+          } }
 {"return": {}}
 65536+0 records in
 65536+0 records out
diff --git a/tests/qemu-iotests/312 b/tests/qemu-iotests/312
new file mode 100755
index 0000000..4134049
--- /dev/null
+++ b/tests/qemu-iotests/312
@@ -0,0 +1,159 @@
+#!/usr/bin/env bash
+#
+# Test drive-mirror with quorum
+#
+# The goal of this test is to check how the quorum driver reports
+# regions that are known to read as zeroes (BDRV_BLOCK_ZERO). The idea
+# is that drive-mirror will try the efficient representation of zeroes
+# in the destination image instead of writing actual zeroes.
+#
+# Copyright (C) 2020 Igalia, S.L.
+# Author: Alberto Garcia <berto@igalia.com>
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+#
+
+# creator
+owner=berto@igalia.com
+
+seq=`basename $0`
+echo "QA output created by $seq"
+
+status=1	# failure is the default!
+
+_cleanup()
+{
+    _rm_test_img "$TEST_IMG.0"
+    _rm_test_img "$TEST_IMG.1"
+    _rm_test_img "$TEST_IMG.2"
+    _rm_test_img "$TEST_IMG.3"
+    _cleanup_qemu
+}
+trap "_cleanup; exit \$status" 0 1 2 3 15
+
+# get standard environment, filters and checks
+. ./common.rc
+. ./common.filter
+. ./common.qemu
+
+_supported_fmt qcow2
+_supported_proto file
+_supported_os Linux
+_unsupported_imgopts cluster_size data_file
+
+echo
+echo '### Create all images' # three source (quorum), one destination
+echo
+TEST_IMG="$TEST_IMG.0" _make_test_img -o cluster_size=64k 10M
+TEST_IMG="$TEST_IMG.1" _make_test_img -o cluster_size=64k 10M
+TEST_IMG="$TEST_IMG.2" _make_test_img -o cluster_size=64k 10M
+TEST_IMG="$TEST_IMG.3" _make_test_img -o cluster_size=64k 10M
+
+quorum="driver=raw,file.driver=quorum,file.vote-threshold=2"
+quorum="$quorum,file.children.0.file.filename=$TEST_IMG.0"
+quorum="$quorum,file.children.1.file.filename=$TEST_IMG.1"
+quorum="$quorum,file.children.2.file.filename=$TEST_IMG.2"
+quorum="$quorum,file.children.0.driver=$IMGFMT"
+quorum="$quorum,file.children.1.driver=$IMGFMT"
+quorum="$quorum,file.children.2.driver=$IMGFMT"
+
+echo
+echo '### Output of qemu-img map (empty quorum)'
+echo
+$QEMU_IMG map --image-opts $quorum | _filter_qemu_img_map
+
+# Now we write data to the quorum. All three images will read as
+# zeroes in all cases, but with different ways to represent them
+# (unallocated clusters, zero clusters, data clusters with zeroes)
+# that will have an effect on how the data will be mirrored and the
+# output of qemu-img map on the resulting image.
+echo
+echo '### Write data to the quorum'
+echo
+# Test 1: data regions surrounded by unallocated clusters.
+# Three data regions, the largest one (0x30000) will be picked, end result:
+# offset 0x10000, length 0x30000 -> data
+$QEMU_IO -c "write -P 0 $((0x10000)) $((0x10000))" "$TEST_IMG.0" | _filter_qemu_io
+$QEMU_IO -c "write -P 0 $((0x10000)) $((0x30000))" "$TEST_IMG.1" | _filter_qemu_io
+$QEMU_IO -c "write -P 0 $((0x10000)) $((0x20000))" "$TEST_IMG.2" | _filter_qemu_io
+
+# Test 2: zero regions surrounded by data clusters.
+# First we allocate the data clusters.
+$QEMU_IO -c "open -o $quorum" -c "write -P 0 $((0x100000)) $((0x40000))" | _filter_qemu_io
+
+# Three zero regions, the smallest one (0x10000) will be picked, end result:
+# offset 0x100000, length 0x10000 -> data
+# offset 0x110000, length 0x10000 -> zeroes
+# offset 0x120000, length 0x20000 -> data
+$QEMU_IO -c "write -z $((0x110000)) $((0x10000))" "$TEST_IMG.0" | _filter_qemu_io
+$QEMU_IO -c "write -z $((0x110000)) $((0x30000))" "$TEST_IMG.1" | _filter_qemu_io
+$QEMU_IO -c "write -z $((0x110000)) $((0x20000))" "$TEST_IMG.2" | _filter_qemu_io
+
+# Test 3: zero clusters surrounded by unallocated clusters.
+# Everything reads as zeroes, no effect on the end result.
+$QEMU_IO -c "write -z $((0x150000)) $((0x10000))" "$TEST_IMG.0" | _filter_qemu_io
+$QEMU_IO -c "write -z $((0x150000)) $((0x30000))" "$TEST_IMG.1" | _filter_qemu_io
+$QEMU_IO -c "write -z $((0x150000)) $((0x20000))" "$TEST_IMG.2" | _filter_qemu_io
+
+# Test 4: mix of data and zero clusters.
+# The zero region will be ignored in favor of the largest data region
+# (0x20000), end result:
+# offset 0x200000, length 0x20000 -> data
+$QEMU_IO -c "write -P 0 $((0x200000)) $((0x10000))" "$TEST_IMG.0" | _filter_qemu_io
+$QEMU_IO -c "write -z   $((0x200000)) $((0x30000))" "$TEST_IMG.1" | _filter_qemu_io
+$QEMU_IO -c "write -P 0 $((0x200000)) $((0x20000))" "$TEST_IMG.2" | _filter_qemu_io
+
+# Test 5: write data to a region and then zeroize it, doing it
+# directly on the quorum device instead of the individual images.
+# This has no effect on the end result but proves that the quorum driver
+# supports 'write -z'.
+$QEMU_IO -c "open -o $quorum" -c "write -P 1 $((0x250000)) $((0x10000))" | _filter_qemu_io
+# Verify the data that we just wrote
+$QEMU_IO -c "open -o $quorum" -c "read -P 1 $((0x250000)) $((0x10000))" | _filter_qemu_io
+$QEMU_IO -c "open -o $quorum" -c "write -z $((0x250000)) $((0x10000))" | _filter_qemu_io
+# Now it should read back as zeroes
+$QEMU_IO -c "open -o $quorum" -c "read -P 0 $((0x250000)) $((0x10000))" | _filter_qemu_io
+
+echo
+echo '### Launch the drive-mirror job'
+echo
+qemu_comm_method="qmp" _launch_qemu -drive if=virtio,"$quorum"
+h=$QEMU_HANDLE
+_send_qemu_cmd $h "{ 'execute': 'qmp_capabilities' }" 'return'
+
+_send_qemu_cmd $h \
+    "{'execute': 'drive-mirror',
+                 'arguments': {'device': 'virtio0',
+                               'format': '$IMGFMT',
+                               'target': '$TEST_IMG.3',
+                               'sync':   'full',
+                               'mode':   'existing' }}"    \
+     "BLOCK_JOB_READY.*virtio0"
+
+_send_qemu_cmd $h \
+    "{ 'execute': 'block-job-complete',
+       'arguments': { 'device': 'virtio0' } }" \
+    'BLOCK_JOB_COMPLETED'
+
+_send_qemu_cmd $h "{ 'execute': 'quit' }" ''
+
+echo
+echo '### Output of qemu-img map (destination image)'
+echo
+$QEMU_IMG map "$TEST_IMG.3" | _filter_qemu_img_map
+
+# success, all done
+echo "*** done"
+rm -f $seq.full
+status=0
diff --git a/tests/qemu-iotests/312.out b/tests/qemu-iotests/312.out
new file mode 100644
index 0000000..5615146
--- /dev/null
+++ b/tests/qemu-iotests/312.out
@@ -0,0 +1,81 @@
+QA output created by 312
+
+### Create all images
+
+Formatting 'TEST_DIR/t.IMGFMT.0', fmt=IMGFMT size=10485760
+Formatting 'TEST_DIR/t.IMGFMT.1', fmt=IMGFMT size=10485760
+Formatting 'TEST_DIR/t.IMGFMT.2', fmt=IMGFMT size=10485760
+Formatting 'TEST_DIR/t.IMGFMT.3', fmt=IMGFMT size=10485760
+
+### Output of qemu-img map (empty quorum)
+
+Offset          Length          File
+
+### Write data to the quorum
+
+wrote 65536/65536 bytes at offset 65536
+64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+wrote 196608/196608 bytes at offset 65536
+192 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+wrote 131072/131072 bytes at offset 65536
+128 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+wrote 262144/262144 bytes at offset 1048576
+256 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+wrote 65536/65536 bytes at offset 1114112
+64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+wrote 196608/196608 bytes at offset 1114112
+192 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+wrote 131072/131072 bytes at offset 1114112
+128 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+wrote 65536/65536 bytes at offset 1376256
+64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+wrote 196608/196608 bytes at offset 1376256
+192 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+wrote 131072/131072 bytes at offset 1376256
+128 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+wrote 65536/65536 bytes at offset 2097152
+64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+wrote 196608/196608 bytes at offset 2097152
+192 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+wrote 131072/131072 bytes at offset 2097152
+128 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+wrote 65536/65536 bytes at offset 2424832
+64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+read 65536/65536 bytes at offset 2424832
+64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+wrote 65536/65536 bytes at offset 2424832
+64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+read 65536/65536 bytes at offset 2424832
+64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+
+### Launch the drive-mirror job
+
+{ 'execute': 'qmp_capabilities' }
+{"return": {}}
+{'execute': 'drive-mirror',
+                 'arguments': {'device': 'virtio0',
+                               'format': 'IMGFMT',
+                               'target': 'TEST_DIR/t.IMGFMT.3',
+                               'sync':   'full',
+                               'mode':   'existing' }}
+{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "created", "id": "virtio0"}}
+{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "running", "id": "virtio0"}}
+{"return": {}}
+{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "ready", "id": "virtio0"}}
+{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "BLOCK_JOB_READY", "data": {"device": "virtio0", "len": 10485760, "offset": 10485760, "speed": 0, "type": "mirror"}}
+{ 'execute': 'block-job-complete',
+       'arguments': { 'device': 'virtio0' } }
+{"return": {}}
+{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "waiting", "id": "virtio0"}}
+{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "pending", "id": "virtio0"}}
+{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "BLOCK_JOB_COMPLETED", "data": {"device": "virtio0", "len": 10485760, "offset": 10485760, "speed": 0, "type": "mirror"}}
+{ 'execute': 'quit' }
+
+### Output of qemu-img map (destination image)
+
+Offset          Length          File
+0x10000         0x30000         TEST_DIR/t.IMGFMT.3
+0x100000        0x10000         TEST_DIR/t.IMGFMT.3
+0x120000        0x20000         TEST_DIR/t.IMGFMT.3
+0x200000        0x20000         TEST_DIR/t.IMGFMT.3
+*** done
diff --git a/tests/qemu-iotests/common.qemu b/tests/qemu-iotests/common.qemu
index de680cf..ef105df 100644
--- a/tests/qemu-iotests/common.qemu
+++ b/tests/qemu-iotests/common.qemu
@@ -146,14 +146,9 @@
         count=${qemu_cmd_repeat}
         use_error="no"
     fi
-    # This array element extraction is done to accommodate pathnames with spaces
-    if [ -z "${success_or_failure}" ]; then
-        cmd=${@: 1:${#@}-1}
-        shift $(($# - 1))
-    else
-        cmd=${@: 1:${#@}-2}
-        shift $(($# - 2))
-    fi
+
+    cmd=$1
+    shift
 
     # Display QMP being sent, but not HMP (since HMP already echoes its
     # input back to output); decide based on leading '{'
diff --git a/tests/qemu-iotests/group b/tests/qemu-iotests/group
index 9a8394b..e4fb632 100644
--- a/tests/qemu-iotests/group
+++ b/tests/qemu-iotests/group
@@ -307,6 +307,7 @@
 295 rw
 296 rw
 297 meta
+298
 299 auto quick
 300 migration
 301 backing quick
@@ -317,3 +318,4 @@
 307 rw quick export
 308 rw
 309 rw auto quick
+312 rw auto quick
diff --git a/tests/qemu-iotests/iotests.py b/tests/qemu-iotests/iotests.py
index bcd4fe5..dcdcd03 100644
--- a/tests/qemu-iotests/iotests.py
+++ b/tests/qemu-iotests/iotests.py
@@ -205,7 +205,12 @@
 
 def qemu_io_silent(*args):
     '''Run qemu-io and return the exit code, suppressing stdout'''
-    args = qemu_io_args + list(args)
+    if '-f' in args or '--image-opts' in args:
+        default_args = qemu_io_args_no_fmt
+    else:
+        default_args = qemu_io_args
+
+    args = default_args + list(args)
     exitcode = subprocess.call(args, stdout=open('/dev/null', 'w'))
     if exitcode < 0:
         sys.stderr.write('qemu-io received signal %i: %s\n' %
@@ -1118,6 +1123,11 @@
     if supported_aio_modes and (aiomode not in supported_aio_modes):
         notrun('not suitable for this aio mode: %s' % aiomode)
 
+def _verify_formats(required_formats: Sequence[str] = ()) -> None:
+    usf_list = list(set(required_formats) - set(supported_formats()))
+    if usf_list:
+        notrun(f'formats {usf_list} are not whitelisted')
+
 def supports_quorum():
     return 'quorum' in qemu_img_pipe('--help')
 
@@ -1275,7 +1285,8 @@
                          supported_aio_modes: Sequence[str] = (),
                          unsupported_fmts: Sequence[str] = (),
                          supported_protocols: Sequence[str] = (),
-                         unsupported_protocols: Sequence[str] = ()) -> bool:
+                         unsupported_protocols: Sequence[str] = (),
+                         required_fmts: Sequence[str] = ()) -> bool:
     """
     Perform necessary setup for either script-style or unittest-style tests.
 
@@ -1301,6 +1312,7 @@
     _verify_platform(supported=supported_platforms)
     _verify_cache_mode(supported_cache_modes)
     _verify_aio_mode(supported_aio_modes)
+    _verify_formats(required_fmts)
 
     return debug