It won't hurt in common case, so let's not bother with detecting image
fleecing.
Also, we want to simplify initialization interface of copy-before-write
filter as we are going to make it public.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
---
block/copy-before-write.h | 2 +-
include/block/block-copy.h | 3 +--
block/backup.c | 20 +-------------------
block/block-copy.c | 29 ++++++++++++++++++++++++++---
block/copy-before-write.c | 4 ++--
5 files changed, 31 insertions(+), 27 deletions(-)
diff --git a/block/copy-before-write.h b/block/copy-before-write.h
index e284dfb6a7..538aab8bdb 100644
--- a/block/copy-before-write.h
+++ b/block/copy-before-write.h
@@ -33,7 +33,7 @@ BlockDriverState *bdrv_cbw_append(BlockDriverState *source,
BlockDriverState *target,
const char *filter_node_name,
uint64_t cluster_size,
- BdrvRequestFlags write_flags,
+ bool compress,
BlockCopyState **bcs,
Error **errp);
void bdrv_cbw_drop(BlockDriverState *bs);
diff --git a/include/block/block-copy.h b/include/block/block-copy.h
index 338f2ea7fd..c013a20e1e 100644
--- a/include/block/block-copy.h
+++ b/include/block/block-copy.h
@@ -24,8 +24,7 @@ typedef struct BlockCopyCallState BlockCopyCallState;
BlockCopyState *block_copy_state_new(BdrvChild *source, BdrvChild *target,
int64_t cluster_size, bool use_copy_range,
- BdrvRequestFlags write_flags,
- Error **errp);
+ bool compress, Error **errp);
void block_copy_set_progress_meter(BlockCopyState *s, ProgressMeter *pm);
diff --git a/block/backup.c b/block/backup.c
index d41dd30e25..29db3a0ef6 100644
--- a/block/backup.c
+++ b/block/backup.c
@@ -407,7 +407,6 @@ BlockJob *backup_job_create(const char *job_id, BlockDriverState *bs,
int64_t len, target_len;
BackupBlockJob *job = NULL;
int64_t cluster_size;
- BdrvRequestFlags write_flags;
BlockDriverState *cbw = NULL;
BlockCopyState *bcs = NULL;
@@ -504,25 +503,8 @@ BlockJob *backup_job_create(const char *job_id, BlockDriverState *bs,
goto error;
}
- /*
- * If source is in backing chain of target assume that target is going to be
- * used for "image fleecing", i.e. it should represent a kind of snapshot of
- * source at backup-start point in time. And target is going to be read by
- * somebody (for example, used as NBD export) during backup job.
- *
- * In this case, we need to add BDRV_REQ_SERIALISING write flag to avoid
- * intersection of backup writes and third party reads from target,
- * otherwise reading from target we may occasionally read already updated by
- * guest data.
- *
- * For more information see commit f8d59dfb40bb and test
- * tests/qemu-iotests/222
- */
- write_flags = (bdrv_chain_contains(target, bs) ? BDRV_REQ_SERIALISING : 0) |
- (compress ? BDRV_REQ_WRITE_COMPRESSED : 0),
-
cbw = bdrv_cbw_append(bs, target, filter_node_name,
- cluster_size, write_flags, &bcs, errp);
+ cluster_size, compress, &bcs, errp);
if (!cbw) {
goto error;
}
diff --git a/block/block-copy.c b/block/block-copy.c
index 9b4af00614..daa1a2bf9f 100644
--- a/block/block-copy.c
+++ b/block/block-copy.c
@@ -245,7 +245,7 @@ static uint32_t block_copy_max_transfer(BdrvChild *source, BdrvChild *target)
BlockCopyState *block_copy_state_new(BdrvChild *source, BdrvChild *target,
int64_t cluster_size, bool use_copy_range,
- BdrvRequestFlags write_flags, Error **errp)
+ bool compress, Error **errp)
{
BlockCopyState *s;
BdrvDirtyBitmap *copy_bitmap;
@@ -257,6 +257,28 @@ BlockCopyState *block_copy_state_new(BdrvChild *source, BdrvChild *target,
}
bdrv_disable_dirty_bitmap(copy_bitmap);
+ /*
+ * Why we always set BDRV_REQ_SERIALISING write flag:
+ *
+ * Assume source is in backing chain of target assume that target is going
+ * to be used for "image fleecing", i.e. it should represent a kind of
+ * snapshot of source at backup-start point in time. And target is going to
+ * be read by somebody (for example, used as NBD export) during backup job.
+ *
+ * In this case, we need to add BDRV_REQ_SERIALISING write flag to avoid
+ * intersection of backup writes and third party reads from target,
+ * otherwise reading from target we may occasionally read already updated by
+ * guest data.
+ *
+ * For more information see commit f8d59dfb40bb and test
+ * tests/qemu-iotests/222
+ *
+ * Other cases? The only known reasonable case is "just copy to target, and
+ * target is not used for something else". In this case BDRV_REQ_SERIALISING
+ * change nothing, so let's not bother with detecting the "image fleecing"
+ * case and enabling BDRV_REQ_SERIALISING only for it.
+ */
+
s = g_new(BlockCopyState, 1);
*s = (BlockCopyState) {
.source = source,
@@ -264,7 +286,8 @@ BlockCopyState *block_copy_state_new(BdrvChild *source, BdrvChild *target,
.copy_bitmap = copy_bitmap,
.cluster_size = cluster_size,
.len = bdrv_dirty_bitmap_size(copy_bitmap),
- .write_flags = write_flags,
+ .write_flags = BDRV_REQ_SERIALISING |
+ (compress ? BDRV_REQ_WRITE_COMPRESSED : 0),
.mem = shres_create(BLOCK_COPY_MAX_MEM),
};
@@ -277,7 +300,7 @@ BlockCopyState *block_copy_state_new(BdrvChild *source, BdrvChild *target,
*/
s->use_copy_range = false;
s->copy_size = cluster_size;
- } else if (write_flags & BDRV_REQ_WRITE_COMPRESSED) {
+ } else if (compress) {
/* Compression supports only cluster-size writes and no copy-range. */
s->use_copy_range = false;
s->copy_size = cluster_size;
diff --git a/block/copy-before-write.c b/block/copy-before-write.c
index bc795adb87..235251a640 100644
--- a/block/copy-before-write.c
+++ b/block/copy-before-write.c
@@ -170,7 +170,7 @@ BlockDriverState *bdrv_cbw_append(BlockDriverState *source,
BlockDriverState *target,
const char *filter_node_name,
uint64_t cluster_size,
- BdrvRequestFlags write_flags,
+ bool compress,
BlockCopyState **bcs,
Error **errp)
{
@@ -216,7 +216,7 @@ BlockDriverState *bdrv_cbw_append(BlockDriverState *source,
state->cluster_size = cluster_size;
state->bcs = block_copy_state_new(top->backing, state->target,
- cluster_size, false, write_flags, errp);
+ cluster_size, false, compress, errp);
if (!state->bcs) {
error_prepend(errp, "Cannot create block-copy-state: ");
goto fail;
--
2.29.2