commit 4bc267a7c7cf204b05d3d1f01625691540a7b965
author Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com> Fri Feb 07 19:12:31 2020 +0300
committer Max Reitz <mreitz@redhat.com> Thu Feb 20 16:43:42 2020 +0100
tree b2fa6bb875cfc5f59f363d319f1776cbd7fa9374
parent 087ab8e775f48766068e65de1bc99d03b40d1670

block/backup-top: fix flags handling

backup-top "supports" write-unchanged, by skipping CBW operation in
backup_top_co_pwritev. But it forgets to do the same in
backup_top_co_pwrite_zeroes, as well as declare support for
BDRV_REQ_WRITE_UNCHANGED.

Fix this, and, while being here, declare also support for flags
supported by source child.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20200207161231.32707-1-vsementsov@virtuozzo.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>

block/backup-top.c

diff --git a/block/backup-top.c b/block/backup-top.c
index fa78f32..1bfb360 100644
--- a/block/backup-top.c
+++ b/block/backup-top.c
@@ -48,11 +48,17 @@
 }
 
 static coroutine_fn int backup_top_cbw(BlockDriverState *bs, uint64_t offset,
-                                       uint64_t bytes)
+                                       uint64_t bytes, BdrvRequestFlags flags)
 {
     BDRVBackupTopState *s = bs->opaque;
-    uint64_t end = QEMU_ALIGN_UP(offset + bytes, s->bcs->cluster_size);
-    uint64_t off = QEMU_ALIGN_DOWN(offset, s->bcs->cluster_size);
+    uint64_t off, end;
+
+    if (flags & BDRV_REQ_WRITE_UNCHANGED) {
+        return 0;
+    }
+
+    off = QEMU_ALIGN_DOWN(offset, s->bcs->cluster_size);
+    end = QEMU_ALIGN_UP(offset + bytes, s->bcs->cluster_size);
 
     return block_copy(s->bcs, off, end - off, NULL);
 }
@@ -60,7 +66,7 @@
 static int coroutine_fn backup_top_co_pdiscard(BlockDriverState *bs,
                                                int64_t offset, int bytes)
 {
-    int ret = backup_top_cbw(bs, offset, bytes);
+    int ret = backup_top_cbw(bs, offset, bytes, 0);
     if (ret < 0) {
         return ret;
     }
@@ -71,7 +77,7 @@
 static int coroutine_fn backup_top_co_pwrite_zeroes(BlockDriverState *bs,
         int64_t offset, int bytes, BdrvRequestFlags flags)
 {
-    int ret = backup_top_cbw(bs, offset, bytes);
+    int ret = backup_top_cbw(bs, offset, bytes, flags);
     if (ret < 0) {
         return ret;
     }
@@ -84,11 +90,9 @@
                                               uint64_t bytes,
                                               QEMUIOVector *qiov, int flags)
 {
-    if (!(flags & BDRV_REQ_WRITE_UNCHANGED)) {
-        int ret = backup_top_cbw(bs, offset, bytes);
-        if (ret < 0) {
-            return ret;
-        }
+    int ret = backup_top_cbw(bs, offset, bytes, flags);
+    if (ret < 0) {
+        return ret;
     }
 
     return bdrv_co_pwritev(bs->backing, offset, bytes, qiov, flags);
@@ -196,8 +200,13 @@
         return NULL;
     }
 
-    top->total_sectors = source->total_sectors;
     state = top->opaque;
+    top->total_sectors = source->total_sectors;
+    top->supported_write_flags = BDRV_REQ_WRITE_UNCHANGED |
+            (BDRV_REQ_FUA & source->supported_write_flags);
+    top->supported_zero_flags = BDRV_REQ_WRITE_UNCHANGED |
+            ((BDRV_REQ_FUA | BDRV_REQ_MAY_UNMAP | BDRV_REQ_NO_FALLBACK) &
+             source->supported_zero_flags);
 
     bdrv_ref(target);
     state->target = bdrv_attach_child(top, target, "target", &child_file, errp);