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Tsirkin" To: Cong Zhang Cc: Jason Wang , Eugenio =?iso-8859-1?Q?P=E9rez?= , Xuan Zhuo , Paolo Bonzini , Stefan Hajnoczi , Jens Axboe , Ming Lei , linux-arm-msm@vger.kernel.org, virtualization@lists.linux.dev, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH v2] virtio_blk: use synchronous quiesce in virtblk_freeze_priv() Message-ID: <20260912050459-mutt-send-email-mst@kernel.org> References: <20260912-virtblk_sync_quiesce-v2-1-09a001549b72@oss.qualcomm.com> Precedence: bulk X-Mailing-List: virtualization@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 In-Reply-To: <20260912-virtblk_sync_quiesce-v2-1-09a001549b72@oss.qualcomm.com> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: knzBOqwN2XfJw8Y5AfqvHFgiadvPEYw2gJQytSJP1zE_1789204190 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline 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(). This repeatition of the code in english is not what we need in the commit log. Suggested format: The following issue was observed by ...: currently .... because ... this is a problem because ... and we can not ... because ... to fix ... so that ... tested by ...: before ... after ... > Fixes: 7678abee0867 ("virtio-blk: don't keep queue frozen during system suspend") > > Signed-off-by: Cong Zhang no empty lines between tags please > --- > 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. this kind of thing belongs in the commit log. > --- > Changes in v2: > - Cc stable@vger.kernel.org. which is no longer there? > - Link to v1: https://lore.kernel.org/20260911-virtblk_sync_quiesce-v1-1-a883f8f31258@oss.qualcomm.com > --- > 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