* [PATCH V3] scsi: core: use blk_mq_requeue_request in __scsi_queue_insert
@ 2018-03-02 3:31 Jianchao Wang
2018-03-02 16:31 ` Bart Van Assche
0 siblings, 1 reply; 3+ messages in thread
From: Jianchao Wang @ 2018-03-02 3:31 UTC (permalink / raw)
To: jejb, martin.petersen
Cc: Bart.VanAssche, linux-scsi, linux-kernel, Christoph Hellwig
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:
V2 -> V3:
- add commit 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 | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index a86df9c..d2f1838 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -191,7 +191,13 @@ 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);
+ /*
+ * scsi_device.sdev_gendev will be get every time in .get_budget and
+ * be put in scsi_end_request. Hence we need to put the reference
+ * here when we decide to requeue request.
+ */
+ blk_mq_requeue_request(cmd->request, true);
+ put_device(&device->sdev_gendev);
return;
}
spin_lock_irqsave(q->queue_lock, flags);
--
2.7.4
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH V3] scsi: core: use blk_mq_requeue_request in __scsi_queue_insert
2018-03-02 3:31 [PATCH V3] scsi: core: use blk_mq_requeue_request in __scsi_queue_insert Jianchao Wang
@ 2018-03-02 16:31 ` Bart Van Assche
2018-03-03 1:41 ` jianchao.wang
0 siblings, 1 reply; 3+ messages in thread
From: Bart Van Assche @ 2018-03-02 16:31 UTC (permalink / raw)
To: jejb, martin.petersen, jianchao.w.wang; +Cc: linux-scsi, linux-kernel, hch
On Fri, 2018-03-02 at 11:31 +0800, Jianchao Wang wrote:
> diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
> index a86df9c..d2f1838 100644
> --- a/drivers/scsi/scsi_lib.c
> +++ b/drivers/scsi/scsi_lib.c
> @@ -191,7 +191,13 @@ 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);
> + /*
> + * scsi_device.sdev_gendev will be get every time in .get_budget and
> + * be put in scsi_end_request. Hence we need to put the reference
> + * here when we decide to requeue request.
> + */
> + blk_mq_requeue_request(cmd->request, true);
> + put_device(&device->sdev_gendev);
> return;
> }
> spin_lock_irqsave(q->queue_lock, flags);
Please consider to change the new comment into something like the following:
"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."
Thanks,
Bart.
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH V3] scsi: core: use blk_mq_requeue_request in __scsi_queue_insert
2018-03-02 16:31 ` Bart Van Assche
@ 2018-03-03 1:41 ` jianchao.wang
0 siblings, 0 replies; 3+ messages in thread
From: jianchao.wang @ 2018-03-03 1:41 UTC (permalink / raw)
To: Bart Van Assche, jejb, martin.petersen; +Cc: linux-scsi, linux-kernel, hch
Hi Bart
Thanks for your kindly response and directive.
On 03/03/2018 12:31 AM, Bart Van Assche wrote:
> On Fri, 2018-03-02 at 11:31 +0800, Jianchao Wang wrote:
>> diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
>> index a86df9c..d2f1838 100644
>> --- a/drivers/scsi/scsi_lib.c
>> +++ b/drivers/scsi/scsi_lib.c
>> @@ -191,7 +191,13 @@ 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);
>> + /*
>> + * scsi_device.sdev_gendev will be get every time in .get_budget and
>> + * be put in scsi_end_request. Hence we need to put the reference
>> + * here when we decide to requeue request.
>> + */
>> + blk_mq_requeue_request(cmd->request, true);
>> + put_device(&device->sdev_gendev);
>> return;
>> }
>> spin_lock_irqsave(q->queue_lock, flags);
>
> Please consider to change the new comment into something like the following:
> "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."
Yes, your comment is more detailed and clearly.
Sincerely
Jianchao
^ permalink raw reply [flat|nested] 3+ messages in thread
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2018-03-02 3:31 [PATCH V3] scsi: core: use blk_mq_requeue_request in __scsi_queue_insert Jianchao Wang
2018-03-02 16:31 ` Bart Van Assche
2018-03-03 1:41 ` jianchao.wang
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