06.08.2020 16:57, Stefan Reiter wrote:
Since commit 42ac214406e0 (block/block-copy: refactor task creation)
block_copy_task_create calculates the area to be copied via
bdrv_dirty_bitmap_next_dirty_area, but that can return an unaligned byte
count if the backing image's last cluster end is not aligned to the
Hmm, I assume you mean not "backing image" but just "image"? Backing seems
unrelated, the problem is just unaligned image
bitmap's granularity.
Always ALIGN_UP the resulting bytes value to satisfy block_copy_do_copy,
which requires the 'bytes' parameter to be aligned to cluster size.
Signed-off-by: Stefan Reiter
---
This causes backups with unaligned image sizes to fail on the last block in my
testing (e.g. a backup job with 4k cluster size fails on a drive with 4097
bytes).
Ohh. Sorry for this :(
I think, we want this case covered by some iotest.. Are you going to add a
test? Or I can do it..
Alternatively one could remove the
assert(QEMU_IS_ALIGNED(bytes, s->cluster_size));
from block_copy_do_copy, but I'd wager that's there for a reason?
Looking at the code I think, that the reason is just a convention. It may be
changed, but it will need an audit of the code. For me your fix looks the
correct thing to do.
block/block-copy.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/block/block-copy.c b/block/block-copy.c
index f7428a7c08..023cb03200 100644
--- a/block/block-copy.c
+++ b/block/block-copy.c
@@ -142,6 +142,8 @@ static BlockCopyTask *block_copy_task_create(BlockCopyState
*s,
return NULL;
}
For readability, I'd also add an assertion:
assert(QEMU_IS_ALIGNED(offset, s->cluster_size));
+bytes = QEMU_ALIGN_UP(bytes, s->cluster_size);
+
/* region is dirty, so no existent tasks possible in it */
assert(!find_conflicting_task(s, offset, bytes));
Thanks for fixing!
Reviewed-by: Vladimir Sementsov-Ogievskiy
--
Best regards,
Vladimir
