* [Qemu-devel] [PATCH bugfix] snapshot: add bdrv_drain_all() to bdrv_snapshot_delete() to avoid concurrency problem
@ 2014-10-21 8:38 Zhang Haoyu
2014-10-21 11:12 ` Paolo Bonzini
2014-10-28 15:18 ` Stefan Hajnoczi
0 siblings, 2 replies; 3+ messages in thread
From: Zhang Haoyu @ 2014-10-21 8:38 UTC (permalink / raw)
To: qemu-devel; +Cc: Kevin Wolf, qemu-stable, Stefan Hajnoczi, Max Reitz
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);
}
--
1.7.12.4
^ permalink raw reply related [flat|nested] 3+ messages in thread* Re: [Qemu-devel] [PATCH bugfix] snapshot: add bdrv_drain_all() to bdrv_snapshot_delete() to avoid concurrency problem
2014-10-21 8:38 [Qemu-devel] [PATCH bugfix] snapshot: add bdrv_drain_all() to bdrv_snapshot_delete() to avoid concurrency problem Zhang Haoyu
@ 2014-10-21 11:12 ` Paolo Bonzini
2014-10-28 15:18 ` Stefan Hajnoczi
1 sibling, 0 replies; 3+ messages in thread
From: Paolo Bonzini @ 2014-10-21 11:12 UTC (permalink / raw)
To: Zhang Haoyu, qemu-devel
Cc: Kevin Wolf, qemu-stable, Stefan Hajnoczi, Max Reitz
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>
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [Qemu-devel] [PATCH bugfix] snapshot: add bdrv_drain_all() to bdrv_snapshot_delete() to avoid concurrency problem
2014-10-21 8:38 [Qemu-devel] [PATCH bugfix] snapshot: add bdrv_drain_all() to bdrv_snapshot_delete() to avoid concurrency problem Zhang Haoyu
2014-10-21 11:12 ` Paolo Bonzini
@ 2014-10-28 15:18 ` Stefan Hajnoczi
1 sibling, 0 replies; 3+ messages in thread
From: Stefan Hajnoczi @ 2014-10-28 15:18 UTC (permalink / raw)
To: Zhang Haoyu
Cc: Kevin Wolf, Max Reitz, qemu-devel, Stefan Hajnoczi, qemu-stable
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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
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^ permalink raw reply [flat|nested] 3+ messages in thread
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2014-10-21 8:38 [Qemu-devel] [PATCH bugfix] snapshot: add bdrv_drain_all() to bdrv_snapshot_delete() to avoid concurrency problem Zhang Haoyu
2014-10-21 11:12 ` Paolo Bonzini
2014-10-28 15:18 ` Stefan Hajnoczi
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