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authorAlberto Garcia <berto@igalia.com>2020-07-10 18:13:12 +0200
committerMax Reitz <mreitz@redhat.com>2020-08-25 08:33:20 +0200
commit40dee94320c9d76a656bd799870f9a81cf520b60 (patch)
tree6eb8eba58b0cd704d417d7e69d0bd15b0614c2ab /block/qcow2.c
parent0dd07b298fdecf13e89c1379b903eb9bb0dac3a3 (diff)
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qcow2: Add prealloc field to QCowL2Meta
This field allows us to indicate that the L2 metadata update does not come from a write request with actual data but from a preallocation request. For traditional images this does not make any difference, but for images with extended L2 entries this means that the clusters are allocated normally in the L2 table but individual subclusters are marked as unallocated. This will allow preallocating images that have a backing file. There is one special case: when we resize an existing image we can also request that the new clusters are preallocated. If the image already had a backing file then we have to hide any possible stale data and zero out the new clusters (see commit 955c7d6687 for more details). In this case the subclusters cannot be left as unallocated so the L2 bitmap must be updated. Signed-off-by: Alberto Garcia <berto@igalia.com> Reviewed-by: Eric Blake <eblake@redhat.com> Reviewed-by: Max Reitz <mreitz@redhat.com> Message-Id: <960d4c444a4f5a870e2b47e5da322a73cd9a2f5a.1594396418.git.berto@igalia.com> Signed-off-by: Max Reitz <mreitz@redhat.com>
Diffstat (limited to 'block/qcow2.c')
-rw-r--r--block/qcow2.c6
1 files changed, 6 insertions, 0 deletions
diff --git a/block/qcow2.c b/block/qcow2.c
index 54c9b7c..7c03d41 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -2096,6 +2096,7 @@ static coroutine_fn int qcow2_handle_l2meta(BlockDriverState *bs,
QCowL2Meta *next;
if (link_l2) {
+ assert(!l2meta->prealloc);
ret = qcow2_alloc_cluster_link_l2(bs, l2meta);
if (ret) {
goto out;
@@ -3130,6 +3131,7 @@ static int coroutine_fn preallocate_co(BlockDriverState *bs, uint64_t offset,
while (meta) {
QCowL2Meta *next = meta->next;
+ meta->prealloc = true;
ret = qcow2_alloc_cluster_link_l2(bs, meta);
if (ret < 0) {
@@ -4217,6 +4219,7 @@ static int coroutine_fn qcow2_co_truncate(BlockDriverState *bs, int64_t offset,
int64_t clusters_allocated;
int64_t old_file_size, last_cluster, new_file_size;
uint64_t nb_new_data_clusters, nb_new_l2_tables;
+ bool subclusters_need_allocation = false;
/* With a data file, preallocation means just allocating the metadata
* and forwarding the truncate request to the data file */
@@ -4298,6 +4301,8 @@ static int coroutine_fn qcow2_co_truncate(BlockDriverState *bs, int64_t offset,
BDRV_REQ_ZERO_WRITE, NULL);
if (ret >= 0) {
flags &= ~BDRV_REQ_ZERO_WRITE;
+ /* Ensure that we read zeroes and not backing file data */
+ subclusters_need_allocation = true;
}
} else {
ret = -1;
@@ -4336,6 +4341,7 @@ static int coroutine_fn qcow2_co_truncate(BlockDriverState *bs, int64_t offset,
.offset = nb_clusters << s->cluster_bits,
.nb_bytes = 0,
},
+ .prealloc = !subclusters_need_allocation,
};
qemu_co_queue_init(&allocation.dependent_requests);