Commit 3432a192 authored Oct 21, 2014 by Zhang Haoyu Committed by Stefan Hajnoczi Nov 03, 2014

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>

parent 573742a5

block/snapshot.c

+4 −0

Original line number	Diff line number	Diff line
		@@ -236,6 +236,10 @@ int bdrv_snapshot_delete(BlockDriverState *bs,
		error_setg(errp, "snapshot_id and name are both NULL");
		return -EINVAL;
		}

		/* drain all pending i/o before deleting snapshot */
		bdrv_drain_all();

		if (drv->bdrv_snapshot_delete) {
		return drv->bdrv_snapshot_delete(bs, snapshot_id, name, errp);
		}