qcow2: Allocate l2meta only for cluster allocations
Even for writes to already allocated clusters, an l2meta is allocated,
though it stays effectively unused. After this patch, only allocating
requests still have one. Each l2meta now describes an in-flight request
that writes to clusters that are not yet hooked up in the L2 table.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
index c4752ee..c2b59e7 100644
--- a/block/qcow2-cluster.c
+++ b/block/qcow2-cluster.c
@@ -652,9 +652,7 @@
uint64_t cluster_offset = m->alloc_offset;
trace_qcow2_cluster_link_l2(qemu_coroutine_self(), m->nb_clusters);
-
- if (m->nb_clusters == 0)
- return 0;
+ assert(m->nb_clusters > 0);
old_cluster = g_malloc(m->nb_clusters * sizeof(uint64_t));
@@ -856,7 +854,7 @@
* Return 0 on success and -errno in error cases
*/
int qcow2_alloc_cluster_offset(BlockDriverState *bs, uint64_t offset,
- int n_start, int n_end, int *num, uint64_t *host_offset, QCowL2Meta *m)
+ int n_start, int n_end, int *num, uint64_t *host_offset, QCowL2Meta **m)
{
BDRVQcowState *s = bs->opaque;
int l2_index, ret, sectors;
@@ -928,11 +926,6 @@
}
/* If there is something left to allocate, do that now */
- *m = (QCowL2Meta) {
- .nb_clusters = 0,
- };
- qemu_co_queue_init(&m->dependent_requests);
-
if (nb_clusters > 0) {
uint64_t alloc_offset;
uint64_t alloc_cluster_offset;
@@ -980,7 +973,9 @@
cluster_offset = alloc_cluster_offset;
}
- *m = (QCowL2Meta) {
+ *m = g_malloc0(sizeof(**m));
+
+ **m = (QCowL2Meta) {
.alloc_offset = alloc_cluster_offset,
.offset = alloc_offset & ~(s->cluster_size - 1),
.nb_clusters = nb_clusters,
@@ -995,8 +990,8 @@
.nb_sectors = avail_sectors - nb_sectors,
},
};
- qemu_co_queue_init(&m->dependent_requests);
- QLIST_INSERT_HEAD(&s->cluster_allocs, m, next_in_flight);
+ qemu_co_queue_init(&(*m)->dependent_requests);
+ QLIST_INSERT_HEAD(&s->cluster_allocs, *m, next_in_flight);
}
}
@@ -1013,8 +1008,8 @@
return 0;
fail:
- if (m->nb_clusters > 0) {
- QLIST_REMOVE(m, next_in_flight);
+ if (*m && (*m)->nb_clusters > 0) {
+ QLIST_REMOVE(*m, next_in_flight);
}
return ret;
}
diff --git a/block/qcow2.c b/block/qcow2.c
index 66ca12f..08d92cc 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -787,8 +787,7 @@
while (remaining_sectors != 0) {
- l2meta = g_malloc0(sizeof(*l2meta));
- qemu_co_queue_init(&l2meta->dependent_requests);
+ l2meta = NULL;
trace_qcow2_writev_start_part(qemu_coroutine_self());
index_in_cluster = sector_num & (s->cluster_sectors - 1);
@@ -799,7 +798,7 @@
}
ret = qcow2_alloc_cluster_offset(bs, sector_num << 9,
- index_in_cluster, n_end, &cur_nr_sectors, &cluster_offset, l2meta);
+ index_in_cluster, n_end, &cur_nr_sectors, &cluster_offset, &l2meta);
if (ret < 0) {
goto fail;
}
@@ -845,14 +844,16 @@
goto fail;
}
- ret = qcow2_alloc_cluster_link_l2(bs, l2meta);
- if (ret < 0) {
- goto fail;
- }
+ if (l2meta != NULL) {
+ ret = qcow2_alloc_cluster_link_l2(bs, l2meta);
+ if (ret < 0) {
+ goto fail;
+ }
- run_dependent_requests(s, l2meta);
- g_free(l2meta);
- l2meta = NULL;
+ run_dependent_requests(s, l2meta);
+ g_free(l2meta);
+ l2meta = NULL;
+ }
remaining_sectors -= cur_nr_sectors;
sector_num += cur_nr_sectors;
@@ -1134,11 +1135,10 @@
uint64_t host_offset = 0;
int num;
int ret;
- QCowL2Meta meta;
+ QCowL2Meta *meta;
nb_sectors = bdrv_getlength(bs) >> 9;
offset = 0;
- qemu_co_queue_init(&meta.dependent_requests);
while (nb_sectors) {
num = MIN(nb_sectors, INT_MAX >> 9);
@@ -1148,15 +1148,17 @@
return ret;
}
- ret = qcow2_alloc_cluster_link_l2(bs, &meta);
+ ret = qcow2_alloc_cluster_link_l2(bs, meta);
if (ret < 0) {
- qcow2_free_any_clusters(bs, meta.alloc_offset, meta.nb_clusters);
+ qcow2_free_any_clusters(bs, meta->alloc_offset, meta->nb_clusters);
return ret;
}
/* There are no dependent requests, but we need to remove our request
* from the list of in-flight requests */
- run_dependent_requests(bs->opaque, &meta);
+ if (meta != NULL) {
+ run_dependent_requests(bs->opaque, meta);
+ }
/* TODO Preallocate data if requested */
diff --git a/block/qcow2.h b/block/qcow2.h
index 24f10012..6dc79b5 100644
--- a/block/qcow2.h
+++ b/block/qcow2.h
@@ -207,7 +207,10 @@
int nb_sectors;
} Qcow2COWRegion;
-/* XXX This could be private for qcow2-cluster.c */
+/**
+ * Describes an in-flight (part of a) write request that writes to clusters
+ * that are not referenced in their L2 table yet.
+ */
typedef struct QCowL2Meta
{
/** Guest offset of the first newly allocated cluster */
@@ -333,7 +336,7 @@
int qcow2_get_cluster_offset(BlockDriverState *bs, uint64_t offset,
int *num, uint64_t *cluster_offset);
int qcow2_alloc_cluster_offset(BlockDriverState *bs, uint64_t offset,
- int n_start, int n_end, int *num, uint64_t *host_offset, QCowL2Meta *m);
+ int n_start, int n_end, int *num, uint64_t *host_offset, QCowL2Meta **m);
uint64_t qcow2_alloc_compressed_cluster_offset(BlockDriverState *bs,
uint64_t offset,
int compressed_size);
