| Message ID | 201410211637596311287@sangfor.com |
|---|---|
| State | New |
| Headers | show |
On 10/21/2014 10:38 AM, Zhang Haoyu wrote: > 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> > --- > block/snapshot.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/block/snapshot.c b/block/snapshot.c > index 85c52ff..ebc386a 100644 > --- a/block/snapshot.c > +++ b/block/snapshot.c > @@ -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); > } > Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
On Tue, Oct 21, 2014 at 04:38:01PM +0800, Zhang Haoyu wrote: > 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> > --- > block/snapshot.c | 4 ++++ > 1 file changed, 4 insertions(+) Thanks, applied to my block tree: https://github.com/stefanha/qemu/commits/block Stefan
diff --git a/block/snapshot.c b/block/snapshot.c index 85c52ff..ebc386a 100644 --- a/block/snapshot.c +++ b/block/snapshot.c @@ -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); }
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> --- block/snapshot.c | 4 ++++ 1 file changed, 4 insertions(+)