block: fix race in bdrv_co_discard with drive-mirror

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>

diff --git a/block/io.c b/block/io.c
index 3527d91aa03fe0e19346619ac260bec17c4bbb9c..8ab6f95477c9116e8291ef6be37c3a5a0d42ca0f 100644 (file)
--- 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;
 }