On Sat, Sep 12, 2026 at 04:52:44PM +0800, Cong Zhang 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")
>
> Signed-off-by: Cong Zhang <[email protected]>
> ---
> 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.
> ---
> Changes in v2:
> - Cc [email protected].
> - Link to v1:
> https://lore.kernel.org/[email protected]
> ---
> drivers/block/virtio_blk.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)Modulo Michael's comments about the commit message: Reviewed-by: Stefan Hajnoczi <[email protected]>
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