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[PATCH v3 08/35] block-copy: always set BDRV_REQ_SERIALISING flag
From: |
Vladimir Sementsov-Ogievskiy |
Subject: |
[PATCH v3 08/35] block-copy: always set BDRV_REQ_SERIALISING flag |
Date: |
Tue, 1 Jun 2021 19:49:59 +0300 |
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 | 21 +--------------------
block/block-copy.c | 29 ++++++++++++++++++++++++++---
block/copy-before-write.c | 4 ++--
5 files changed, 31 insertions(+), 28 deletions(-)
diff --git a/block/copy-before-write.h b/block/copy-before-write.h
index 5977b7aa31..f37e2249ae 100644
--- a/block/copy-before-write.h
+++ b/block/copy-before-write.h
@@ -34,7 +34,7 @@ BlockDriverState *bdrv_cbw_append(BlockDriverState *source,
const char *filter_node_name,
uint64_t cluster_size,
BackupPerf *perf,
- 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 ac91821b08..84f9a5f02c 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;
@@ -504,26 +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, perf,
- write_flags, &bcs, errp);
+ cluster_size, perf, compress, &bcs, errp);
if (!cbw) {
goto error;
}
diff --git a/block/block-copy.c b/block/block-copy.c
index c2e5090412..57dfef61f3 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 0dc5a107cf..4337076c1c 100644
--- a/block/copy-before-write.c
+++ b/block/copy-before-write.c
@@ -171,7 +171,7 @@ BlockDriverState *bdrv_cbw_append(BlockDriverState *source,
const char *filter_node_name,
uint64_t cluster_size,
BackupPerf *perf,
- BdrvRequestFlags write_flags,
+ bool compress,
BlockCopyState **bcs,
Error **errp)
{
@@ -218,7 +218,7 @@ BlockDriverState *bdrv_cbw_append(BlockDriverState *source,
state->cluster_size = cluster_size;
state->bcs = block_copy_state_new(top->backing, state->target,
cluster_size, perf->use_copy_range,
- write_flags, errp);
+ compress, errp);
if (!state->bcs) {
error_prepend(errp, "Cannot create block-copy-state: ");
goto fail;
--
2.29.2
- [PATCH v3 01/35] block: rename bdrv_replace_child to bdrv_replace_child_tran, (continued)
- [PATCH v3 01/35] block: rename bdrv_replace_child to bdrv_replace_child_tran, Vladimir Sementsov-Ogievskiy, 2021/06/01
- [PATCH v3 02/35] block: comment graph-modifying function not updating permissions, Vladimir Sementsov-Ogievskiy, 2021/06/01
- [PATCH v3 03/35] block: introduce bdrv_replace_child_bs(), Vladimir Sementsov-Ogievskiy, 2021/06/01
- [PATCH v3 09/35] block/block-copy: introduce block_copy_set_copy_opts(), Vladimir Sementsov-Ogievskiy, 2021/06/01
- [PATCH v3 04/35] block: introduce blk_replace_bs, Vladimir Sementsov-Ogievskiy, 2021/06/01
- [PATCH v3 10/35] block/backup: set copy_range and compress after filter insertion, Vladimir Sementsov-Ogievskiy, 2021/06/01
- [PATCH v3 05/35] qdev-properties: PropertyInfo: add realized_set_allowed field, Vladimir Sementsov-Ogievskiy, 2021/06/01
- [PATCH v3 06/35] qdev: allow setting drive property for realized device, Vladimir Sementsov-Ogievskiy, 2021/06/01
- [PATCH v3 07/35] block: rename backup-top to copy-before-write, Vladimir Sementsov-Ogievskiy, 2021/06/01
- [PATCH v3 11/35] block/backup: move cluster size calculation to block-copy, Vladimir Sementsov-Ogievskiy, 2021/06/01
- [PATCH v3 08/35] block-copy: always set BDRV_REQ_SERIALISING flag,
Vladimir Sementsov-Ogievskiy <=
- [PATCH v3 14/35] block/copy-before-write: use file child instead of backing, Vladimir Sementsov-Ogievskiy, 2021/06/01
- [PATCH v3 13/35] block/copy-before-write: drop extra bdrv_unref on failure path, Vladimir Sementsov-Ogievskiy, 2021/06/01
- [PATCH v3 15/35] block/copy-before-write: bdrv_cbw_append(): replace child at last, Vladimir Sementsov-Ogievskiy, 2021/06/01
- [PATCH v3 12/35] block/copy-before-write: relax permission requirements when no parents, Vladimir Sementsov-Ogievskiy, 2021/06/01
- [PATCH v3 16/35] block/copy-before-write: introduce cbw_init(), Vladimir Sementsov-Ogievskiy, 2021/06/01
- [PATCH v3 17/35] block/copy-before-write: cbw_init(): rename variables, Vladimir Sementsov-Ogievskiy, 2021/06/01
- [PATCH v3 19/35] block/copy-before-write: bdrv_cbw_append(): drop unused compress arg, Vladimir Sementsov-Ogievskiy, 2021/06/01
- [PATCH v3 18/35] block/copy-before-write: cbw_init(): use file child after attaching, Vladimir Sementsov-Ogievskiy, 2021/06/01
- [PATCH v3 21/35] block/copy-before-write: initialize block-copy bitmap, Vladimir Sementsov-Ogievskiy, 2021/06/01
- [PATCH v3 20/35] block/copy-before-write: cbw_init(): use options, Vladimir Sementsov-Ogievskiy, 2021/06/01