03.07.2018 21:07, Vladimir Sementsov-Ogievskiy wrote:
Serialized writes should be used in copy-on-write of backup(sync=none)
for image fleecing scheme.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsement...@virtuozzo.com>
---
include/block/block.h | 5 ++++-
block/io.c | 4 ++++
2 files changed, 8 insertions(+), 1 deletion(-)
diff --git a/include/block/block.h b/include/block/block.h
index e5c7759a0c..107113aad5 100644
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -58,8 +58,11 @@ typedef enum {
* content. */
BDRV_REQ_WRITE_UNCHANGED = 0x40,
+ /* Force request serializing. Only for writes. */
+ BDRV_REQ_SERIALISING = 0x80,
+
/* Mask of valid flags */
- BDRV_REQ_MASK = 0x7f,
+ BDRV_REQ_MASK = 0xff,
} BdrvRequestFlags;
typedef struct BlockSizes {
diff --git a/block/io.c b/block/io.c
index 1a2272fad3..d5ba078514 100644
--- a/block/io.c
+++ b/block/io.c
@@ -1572,6 +1572,10 @@ static int coroutine_fn bdrv_aligned_pwritev(BdrvChild
*child,
max_transfer = QEMU_ALIGN_DOWN(MIN_NON_ZERO(bs->bl.max_transfer, INT_MAX),
align);
+ if (flags & BDRV_REQ_SERIALISING) {
+ mark_request_serialising(req, bdrv_get_cluster_size(bs));
+ }
+
waited = wait_serialising_requests(req);
assert(!waited || !req->serialising);
Kevin, about this assertion, introduced in 28de2dcd88de "block: Assert
serialisation assumptions in pwritev"? Will not it fail with fleecing
scheme? I'm afraid it will, when we will wait for client read with our
request, marked serializing a moment ago...
Can we just switch it to assert(!waited || !req->partial);, setting
req->partial in bdrv_co_pwritev for parts of unaligned requests? And
allow new flag only for aligned requests?
Other ideas?
assert(req->overlap_offset <= offset);
--
Best regards,
Vladimir
