[Qemu-devel] [PULL 11/20] block: fix race in bdrv_co_discard with drive-mirror

[Stefan Hajnoczi <stefanha@redhat.com>]

From: "Denis V. Lunev" <den@openvz.org>

Actually we must set dirty bitmap dirty after we have written all our
zeroes for correct processing in drive mirror code. In the other case
we can face not zeroes in this area in mirror_iteration.

Signed-off-by: Denis V. Lunev <den@openvz.org>
Reviewed-by: Vladimir Sementsov-Ogievskiy<vsementsov@virtuozzo.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-id: 1466093381-6120-3-git-send-email-den@openvz.org
CC: Stefan Hajnoczi <stefanha@redhat.com>
CC: Kevin Wolf <kwolf@redhat.com>
CC: Max Reitz <mreitz@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 block/io.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/block/io.c b/block/io.c
index 3527d91..8ab6f95 100644
--- a/block/io.c
+++ b/block/io.c
@@ -2349,7 +2349,6 @@ int coroutine_fn bdrv_co_discard(BlockDriverState *bs, int64_t sector_num,
 
     tracked_request_begin(&req, bs, sector_num << BDRV_SECTOR_BITS,
                           nb_sectors << BDRV_SECTOR_BITS, BDRV_TRACKED_DISCARD);
-    bdrv_set_dirty(bs, sector_num, nb_sectors);
 
     max_discard = MIN_NON_ZERO(bs->bl.max_discard, BDRV_REQUEST_MAX_SECTORS);
     while (nb_sectors > 0) {
@@ -2398,6 +2397,8 @@ int coroutine_fn bdrv_co_discard(BlockDriverState *bs, int64_t sector_num,
     }
     ret = 0;
 out:
+    bdrv_set_dirty(bs, req.offset >> BDRV_SECTOR_BITS,
+                   req.bytes >> BDRV_SECTOR_BITS);
     tracked_request_end(&req);
     return ret;
 }
-- 
2.5.5