* [PATCH] virtio_blk: use synchronous quiesce in virtblk_freeze_priv()
@ 2026-09-10 16:31 Cong Zhang
2026-09-11 2:22 ` Jason Wang
0 siblings, 1 reply; 3+ messages in thread
From: Cong Zhang @ 2026-09-10 16:31 UTC (permalink / raw)
To: Michael S. Tsirkin, Jason Wang, Eugenio Pérez, Xuan Zhuo,
Paolo Bonzini, Stefan Hajnoczi, Jens Axboe, Ming Lei
Cc: linux-arm-msm, virtualization, linux-block, linux-kernel,
Cong Zhang
Replace blk_mq_quiesce_queue_nowait() with blk_mq_quiesce_queue() in
virtblk_freeze_priv().
Keep the existing freeze and unfreeze order. The synchronous call waits
for dispatch code that was already running. The queue remains quiesced
until virtblk_restore_priv() calls blk_mq_unquiesce_queue().
Fixes: 7678abee0867 ("virtio-blk: don't keep queue frozen during system suspend")
Signed-off-by: Cong Zhang <cong.zhang@oss.qualcomm.com>
---
blk_mq_run_work_fn() can call blk_mq_sched_dispatch_requests() through
blk_mq_run_dispatch_ops(). The dispatcher checks QUEUE_FLAG_QUIESCED
while the flag is clear. It can then be preempted before it gets a
request. At that time, it has no queue usage reference, so
blk_mq_freeze_queue() does not wait for it.
virtblk_freeze_priv() then calls blk_mq_quiesce_queue_nowait() and
blk_mq_unfreeze_queue(). A new request can enter the queue. The old
dispatcher can run again, use its old flag check, get the new request,
and call virtio_queue_rq(). At the same time, virtblk_freeze_priv() can
reset the device, delete the virtqueues, and free vblk->vqs. The old
dispatcher can then use a deleted virtqueue or a NULL vblk->vqs, and the
kernel can crash.
---
drivers/block/virtio_blk.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
index 32bf3ba07a9d..7a570591e040 100644
--- a/drivers/block/virtio_blk.c
+++ b/drivers/block/virtio_blk.c
@@ -1595,7 +1595,7 @@ static int virtblk_freeze_priv(struct virtio_device *vdev)
/* Ensure no requests in virtqueues before deleting vqs. */
memflags = blk_mq_freeze_queue(q);
- blk_mq_quiesce_queue_nowait(q);
+ blk_mq_quiesce_queue(q);
blk_mq_unfreeze_queue(q, memflags);
/* Ensure we don't receive any more interrupts */
---
base-commit: 50d05c7c76c96b90462f24debacca971d2e86713
change-id: 20260910-virtblk_sync_quiesce-9b2c88d45416
Best regards,
--
Cong Zhang <cong.zhang@oss.qualcomm.com>
^ permalink raw reply related [flat|nested] 3+ messages in thread* Re: [PATCH] virtio_blk: use synchronous quiesce in virtblk_freeze_priv()
2026-09-10 16:31 [PATCH] virtio_blk: use synchronous quiesce in virtblk_freeze_priv() Cong Zhang
@ 2026-09-11 2:22 ` Jason Wang
2026-09-11 9:05 ` Cong Zhang
0 siblings, 1 reply; 3+ messages in thread
From: Jason Wang @ 2026-09-11 2:22 UTC (permalink / raw)
To: Cong Zhang
Cc: Michael S. Tsirkin, Eugenio Pérez, Xuan Zhuo, Paolo Bonzini,
Stefan Hajnoczi, Jens Axboe, Ming Lei, linux-arm-msm,
virtualization, linux-block, linux-kernel
On Fri, Sep 11, 2026 at 12:31 AM Cong Zhang <cong.zhang@oss.qualcomm.com> wrote:
>
> Replace blk_mq_quiesce_queue_nowait() with blk_mq_quiesce_queue() in
> virtblk_freeze_priv().
>
> Keep the existing freeze and unfreeze order. The synchronous call waits
> for dispatch code that was already running. The queue remains quiesced
> until virtblk_restore_priv() calls blk_mq_unquiesce_queue().
>
> Fixes: 7678abee0867 ("virtio-blk: don't keep queue frozen during system suspend")
>
Do we need this for -stable?
> Signed-off-by: Cong Zhang <cong.zhang@oss.qualcomm.com>
> ---
> blk_mq_run_work_fn() can call blk_mq_sched_dispatch_requests() through
> blk_mq_run_dispatch_ops(). The dispatcher checks QUEUE_FLAG_QUIESCED
> while the flag is clear. It can then be preempted before it gets a
> request. At that time, it has no queue usage reference, so
> blk_mq_freeze_queue() does not wait for it.
>
> virtblk_freeze_priv() then calls blk_mq_quiesce_queue_nowait() and
> blk_mq_unfreeze_queue(). A new request can enter the queue. The old
> dispatcher can run again, use its old flag check, get the new request,
> and call virtio_queue_rq(). At the same time, virtblk_freeze_priv() can
> reset the device, delete the virtqueues, and free vblk->vqs. The old
> dispatcher can then use a deleted virtqueue or a NULL vblk->vqs, and the
> kernel can crash.
> ---
> drivers/block/virtio_blk.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
> index 32bf3ba07a9d..7a570591e040 100644
> --- a/drivers/block/virtio_blk.c
> +++ b/drivers/block/virtio_blk.c
> @@ -1595,7 +1595,7 @@ static int virtblk_freeze_priv(struct virtio_device *vdev)
>
> /* Ensure no requests in virtqueues before deleting vqs. */
> memflags = blk_mq_freeze_queue(q);
> - blk_mq_quiesce_queue_nowait(q);
> + blk_mq_quiesce_queue(q);
> blk_mq_unfreeze_queue(q, memflags);
>
> /* Ensure we don't receive any more interrupts */
>
> ---
> base-commit: 50d05c7c76c96b90462f24debacca971d2e86713
> change-id: 20260910-virtblk_sync_quiesce-9b2c88d45416
>
> Best regards,
> --
> Cong Zhang <cong.zhang@oss.qualcomm.com>
>
Other than this,
Acked-by: Jason Wang <jasowangio@gmail.com>
Thanks
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [PATCH] virtio_blk: use synchronous quiesce in virtblk_freeze_priv()
2026-09-11 2:22 ` Jason Wang
@ 2026-09-11 9:05 ` Cong Zhang
0 siblings, 0 replies; 3+ messages in thread
From: Cong Zhang @ 2026-09-11 9:05 UTC (permalink / raw)
To: Jason Wang
Cc: Michael S. Tsirkin, Eugenio Pérez, Xuan Zhuo, Paolo Bonzini,
Stefan Hajnoczi, Jens Axboe, Ming Lei, linux-arm-msm,
virtualization, linux-block, linux-kernel
On 9/11/2026 10:22 AM, Jason Wang wrote:
> On Fri, Sep 11, 2026 at 12:31 AM Cong Zhang <cong.zhang@oss.qualcomm.com> wrote:
>>
>> Replace blk_mq_quiesce_queue_nowait() with blk_mq_quiesce_queue() in
>> virtblk_freeze_priv().
>>
>> Keep the existing freeze and unfreeze order. The synchronous call waits
>> for dispatch code that was already running. The queue remains quiesced
>> until virtblk_restore_priv() calls blk_mq_unquiesce_queue().
>>
>> Fixes: 7678abee0867 ("virtio-blk: don't keep queue frozen during system suspend")
>>
>
> Do we need this for -stable?
>
Good point, I will add this in V2.
>> Signed-off-by: Cong Zhang <cong.zhang@oss.qualcomm.com>
>> ---
>> blk_mq_run_work_fn() can call blk_mq_sched_dispatch_requests() through
>> blk_mq_run_dispatch_ops(). The dispatcher checks QUEUE_FLAG_QUIESCED
>> while the flag is clear. It can then be preempted before it gets a
>> request. At that time, it has no queue usage reference, so
>> blk_mq_freeze_queue() does not wait for it.
>>
>> virtblk_freeze_priv() then calls blk_mq_quiesce_queue_nowait() and
>> blk_mq_unfreeze_queue(). A new request can enter the queue. The old
>> dispatcher can run again, use its old flag check, get the new request,
>> and call virtio_queue_rq(). At the same time, virtblk_freeze_priv() can
>> reset the device, delete the virtqueues, and free vblk->vqs. The old
>> dispatcher can then use a deleted virtqueue or a NULL vblk->vqs, and the
>> kernel can crash.
>> ---
>> drivers/block/virtio_blk.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
>> index 32bf3ba07a9d..7a570591e040 100644
>> --- a/drivers/block/virtio_blk.c
>> +++ b/drivers/block/virtio_blk.c
>> @@ -1595,7 +1595,7 @@ static int virtblk_freeze_priv(struct virtio_device *vdev)
>>
>> /* Ensure no requests in virtqueues before deleting vqs. */
>> memflags = blk_mq_freeze_queue(q);
>> - blk_mq_quiesce_queue_nowait(q);
>> + blk_mq_quiesce_queue(q);
>> blk_mq_unfreeze_queue(q, memflags);
>>
>> /* Ensure we don't receive any more interrupts */
>>
>> ---
>> base-commit: 50d05c7c76c96b90462f24debacca971d2e86713
>> change-id: 20260910-virtblk_sync_quiesce-9b2c88d45416
>>
>> Best regards,
>> --
>> Cong Zhang <cong.zhang@oss.qualcomm.com>
>>
>
> Other than this,
>
> Acked-by: Jason Wang <jasowangio@gmail.com>
>
> Thanks
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2026-09-11 9:05 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2026-09-10 16:31 [PATCH] virtio_blk: use synchronous quiesce in virtblk_freeze_priv() Cong Zhang
2026-09-11 2:22 ` Jason Wang
2026-09-11 9:05 ` Cong Zhang
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox