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snapshot: add bdrv_drain_all() to bdrv_snapshot_delete() to avoid concurrency problem 

If there are still pending i/o while deleting snapshot,
because deleting snapshot is done in non-coroutine context, and
the pending i/o read/write (bdrv_co_do_rw) is done in coroutine context,
so it's possible to cause concurrency problem between above two operations.
Add bdrv_drain_all() to bdrv_snapshot_delete() to avoid this problem.

Signed-off-by: Zhang Haoyu <zhanghy@sangfor.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Message-id: 201410211637596311287@sangfor.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Zhang Haoyu 2014-10-21 16:38:01 +08:00 committed by Stefan Hajnoczi
parent 573742a543
commit 3432a1929e
1 changed files with 4 additions and 0 deletions
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4
block/snapshot.c
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@ -236,6 +236,10 @@ int bdrv_snapshot_delete(BlockDriverState *bs,
error_setg(errp, "snapshot_id and name are both NULL"); error_setg(errp, "snapshot_id and name are both NULL");
return -EINVAL; return -EINVAL;
} }
/* drain all pending i/o before deleting snapshot */
bdrv_drain_all();
if (drv->bdrv_snapshot_delete) { if (drv->bdrv_snapshot_delete) {
return drv->bdrv_snapshot_delete(bs, snapshot_id, name, errp); return drv->bdrv_snapshot_delete(bs, snapshot_id, name, errp);
} }