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Tsirkin" , Jason Wang , Eugenio Perez , Xuan Zhuo , Paolo Bonzini , Stefan Hajnoczi , Jens Axboe , Ming Lei Cc: linux-arm-msm@vger.kernel.org, virtualization@lists.linux.dev, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org References: <20260928-virtblk_sync_quiesce-v3-1-a037e6e2fdf5@oss.qualcomm.com> Content-Language: en-US From: Cong Zhang In-Reply-To: <20260928-virtblk_sync_quiesce-v3-1-a037e6e2fdf5@oss.qualcomm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYxMDE2MDA0MiBTYWx0ZWRfX/Lcll1t5u860 W6ZVP/Vz70MUvEb32CDUHvHcnyeqA9JbgZDf5ZYSst8d0FRyFMT52s3k/yAMZPxpyKRtsWPHOzm 0JslZPSQTbBDiROOghfb5UnUZUYBua/6Qb2RUcMApYyeYUOzCNPn9jWYYrTODg6m5HM0lskKoQW k/Ky+X5eNbcrQqVj+H3A0PcYOwH5YAUz8fz6Hnm01jsANH3+sU9DJI8TiP6CU+AISTieFdTS0SK hlf3cc5aB/Cngiv8O17A7TBx76Sb7fyQznPsOFbsH201QDcjfSOGA3iavNA2m/dVkNGk9ZikZie 9lfFIezHSBXJP6qXNSF/of6sDffiIKK6nQrjnXv4UAdASTgrmkjJ3VB7xgzHI3QGP/KVxfNY25n n2pMlXxlgXwyqWa2gMnZK9II7LkVjpIxWoJsM6R5pXTYB2cpPr00rrPwTN7K1cCMiUsKCwRDgBo C2A2L1R40ITmlGhG24Q== X-Proofpoint-Spam-Info: AW1haW4tMjYxMDE2MDA0MiBTYWx0ZWRfX5J0E+EPRiZ6n alklhflOzx0nlQiiElMTrtcDreCkEGOGhlRGCG+J6uKlJUMAyacPcCWwueh5is5L9YuZfDRHKza sOz1tHJaq2ZHtDbmqY8y1chbZqhLOMQ= X-Authority-Analysis: v=2.4 cv=PqsG/AM3 c=1 sm=1 tr=0 ts=6ad20038 cx=c_pps a=WW5sKcV1LcKqjgzy2JUPuA==:117 a=Uz3yg00KUFJ2y2WijEJ4bw==:17 a=IkcTkHD0fZMA:10 a=660iZSQnnn4A:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=u7WPNUs3qKkmUXheDGA7:22 a=yx91gb_oNiZeI1HMLzn7:22 a=VwQbUJbxAAAA:8 a=EUspDBNiAAAA:8 a=pGLkceISAAAA:8 a=20KFwNOVAAAA:8 a=BM0rjV1Hin7eb0uZrgEA:9 a=QEXdDO2ut3YA:10 a=OpyuDcXvxspvyRM73sMx:22 X-Proofpoint-ORIG-GUID: 91aE9gvFZ88kUOK4vIjMJjQmW2X63-V3 X-Proofpoint-GUID: 91aE9gvFZ88kUOK4vIjMJjQmW2X63-V3 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1176,Hydra:6.1.134,FMLib:17.12.100.49 definitions=2026-10-16_01,2026-10-14_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 bulkscore=0 priorityscore=1501 lowpriorityscore=0 impostorscore=0 phishscore=0 clxscore=1015 malwarescore=0 suspectscore=0 adultscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2610080000 definitions=main-2610160042 Gentle reminder on this patch. Any feedback would be appreciated. On 9/28/2026 7:58 PM, Cong Zhang wrote: > 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. > > Fix this by using blk_mq_quiesce_queue(), which waits for dispatch code > that was already running. Keep the existing freeze and unfreeze order. > 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") > Cc: stable@vger.kernel.org > Acked-by: Jason Wang > Reviewed-by: Stefan Hajnoczi > Signed-off-by: Cong Zhang > --- > Changes in v3: > - Move the race description into the commit log. > - Remove the blank line between tags. > - Add Cc: stable@vger.kernel.org to the commit trailers. > - Link to v2: https://lore.kernel.org/20260912-virtblk_sync_quiesce-v2-1-09a001549b72@oss.qualcomm.com > > Changes in v2: > - Cc stable@vger.kernel.org. > - 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 >