| Message ID | 1520042049-8874-1-git-send-email-jianchao.w.wang@oracle.com (mailing list archive) |
|---|---|
| State | Accepted |
| Headers | show |
Hi Martin Can you take your precious time to review this ? Thanks in advice. Jianchao On 03/03/2018 09:54 AM, Jianchao Wang wrote: > In scsi core, __scsi_queue_insert should just put request back on > the queue and retry using the same command as before. However, for > blk-mq, scsi_mq_requeue_cmd is employed here which will unprepare > the request. To align with the semantics of __scsi_queue_insert, > use blk_mq_requeue_request with kick_requeue_list == true and put > the reference of scsi_device. > > Cc: Christoph Hellwig <hch@lst.de> > Signed-off-by: Jianchao Wang <jianchao.w.wang@oracle.com> > Reviewed-by: Bart Van Assche <bart.vanassche@wdc.com> > --- > Changelog: > V3 -> V4: > - modify the comment and make it more clearly > > V2 -> V3: > - add comment to explain why we need a put_device in > __scsi_queue_insert > - add reviewed-by > > V1 -> V2: > - add put_device on scsi_device->sdev_gendev > drivers/scsi/scsi_lib.c | 14 +++++++++++++- > 1 file changed, 13 insertions(+), 1 deletion(-) > > diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c > index a86df9c..6ce33f6 100644 > --- a/drivers/scsi/scsi_lib.c > +++ b/drivers/scsi/scsi_lib.c > @@ -191,7 +191,19 @@ static void __scsi_queue_insert(struct scsi_cmnd *cmd, int reason, bool unbusy) > */ > cmd->result = 0; > if (q->mq_ops) { > - scsi_mq_requeue_cmd(cmd); > + /* > + * Before a SCSI command is dispatched, > + * get_device(&sdev->sdev_gendev) is called and the host, > + * target and device busy counters are increased. Since > + * requeuing a request causes these actions to be repeated and > + * since scsi_device_unbusy() has already been called, > + * put_device(&device->sdev_gendev) must still be called. Call > + * put_device() after blk_mq_requeue_request() to avoid that > + * removal of the SCSI device can start before requeueing has > + * happened. > + */ > + blk_mq_requeue_request(cmd->request, true); > + put_device(&device->sdev_gendev); > return; > } > spin_lock_irqsave(q->queue_lock, flags); >
Jianchao, > In scsi core, __scsi_queue_insert should just put request back on > the queue and retry using the same command as before. However, for > blk-mq, scsi_mq_requeue_cmd is employed here which will unprepare > the request. To align with the semantics of __scsi_queue_insert, > use blk_mq_requeue_request with kick_requeue_list == true and put > the reference of scsi_device. Applied to 4.17/scsi-queue, thank you!
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c index a86df9c..6ce33f6 100644 --- a/drivers/scsi/scsi_lib.c +++ b/drivers/scsi/scsi_lib.c @@ -191,7 +191,19 @@ static void __scsi_queue_insert(struct scsi_cmnd *cmd, int reason, bool unbusy) */ cmd->result = 0; if (q->mq_ops) { - scsi_mq_requeue_cmd(cmd); + /* + * Before a SCSI command is dispatched, + * get_device(&sdev->sdev_gendev) is called and the host, + * target and device busy counters are increased. Since + * requeuing a request causes these actions to be repeated and + * since scsi_device_unbusy() has already been called, + * put_device(&device->sdev_gendev) must still be called. Call + * put_device() after blk_mq_requeue_request() to avoid that + * removal of the SCSI device can start before requeueing has + * happened. + */ + blk_mq_requeue_request(cmd->request, true); + put_device(&device->sdev_gendev); return; } spin_lock_irqsave(q->queue_lock, flags);