[Qemu-block] [PATCH 2/3] block: fix race in bdrv_co_discard with drive-mirror

[Denis V. Lunev]

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 dirty area there in mirror_iteration.

Signed-off-by: Denis V. Lunev <address@hidden>
CC: Vladimir Sementsov-Ogievskiy<address@hidden>
CC: Stefan Hajnoczi <address@hidden>
CC: Fam Zheng <address@hidden>
CC: Kevin Wolf <address@hidden>
CC: Max Reitz <address@hidden>
---
 block/io.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/block/io.c b/block/io.c
index b51f681..513bd99 100644
--- a/block/io.c
+++ b/block/io.c
@@ -2265,7 +2265,6 @@ int coroutine_fn bdrv_co_discard(BlockDriverState *bs, 
int64_t sector_num,
 
     tracked_request_begin(&req, bs, NULL, 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) {
@@ -2314,6 +2313,8 @@ 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;
 }
-- 
2.5.0