2023-05-15 07:18:02

by Wenchao Hao

Subject: [PATCH 2/2] scsi: core: decrease scsi_device's iorequest_cnt if dispatch failed

If scsi_dispatch_cmd() failed, the SCSI command was not sent to the target,
scsi_queue_rq() would return BLK_STS_RESOURCE and the related request
would be requeued. The timeout of this request would not fire, no one would
increase iodone_cnt.

The above flow would result the iodone_cnt smaller than iorequest_cnt.
So decrease the iorequest_cnt if dispatch failed to workaround the issue.

Link:https://lore.kernel.org/linux-scsi/[email protected]/T/#t

Signed-off-by: Wenchao Hao <[email protected]>
---
drivers/scsi/scsi_lib.c | 2 ++
1 file changed, 2 insertions(+)

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 03964b26f3f2..0226c9279cef 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -1485,6 +1485,7 @@ static int scsi_dispatch_cmd(struct scsi_cmnd *cmd)
*/
SCSI_LOG_MLQUEUE(3, scmd_printk(KERN_INFO, cmd,
"queuecommand : device blocked\n"));
+ atomic_dec(&cmd->device->iorequest_cnt);
return SCSI_MLQUEUE_DEVICE_BUSY;
}

@@ -1517,6 +1518,7 @@ static int scsi_dispatch_cmd(struct scsi_cmnd *cmd)
trace_scsi_dispatch_cmd_start(cmd);
rtn = host->hostt->queuecommand(host, cmd);
if (rtn) {
+ atomic_dec(&cmd->device->iorequest_cnt);
trace_scsi_dispatch_cmd_error(cmd, rtn);
if (rtn != SCSI_MLQUEUE_DEVICE_BUSY &&
rtn != SCSI_MLQUEUE_TARGET_BUSY)
--
2.32.0

2023-05-15 09:02:57

by Ming Lei

Subject: Re: [PATCH 2/2] scsi: core: decrease scsi_device's iorequest_cnt if dispatch failed

On Mon, May 15, 2023 at 03:01:56PM +0800, Wenchao Hao wrote:
> If scsi_dispatch_cmd() failed, the SCSI command was not sent to the target,
> scsi_queue_rq() would return BLK_STS_RESOURCE and the related request
> would be requeued. The timeout of this request would not fire, no one would
> increase iodone_cnt.
>
> The above flow would result the iodone_cnt smaller than iorequest_cnt.
> So decrease the iorequest_cnt if dispatch failed to workaround the issue.
>
> Link:https://lore.kernel.org/linux-scsi/[email protected]/T/#t
>
> Signed-off-by: Wenchao Hao <[email protected]>
> ---
> drivers/scsi/scsi_lib.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
> index 03964b26f3f2..0226c9279cef 100644
> --- a/drivers/scsi/scsi_lib.c
> +++ b/drivers/scsi/scsi_lib.c
> @@ -1485,6 +1485,7 @@ static int scsi_dispatch_cmd(struct scsi_cmnd *cmd)
> */
> SCSI_LOG_MLQUEUE(3, scmd_printk(KERN_INFO, cmd,
> "queuecommand : device blocked\n"));
> + atomic_dec(&cmd->device->iorequest_cnt);
> return SCSI_MLQUEUE_DEVICE_BUSY;
> }
>
> @@ -1517,6 +1518,7 @@ static int scsi_dispatch_cmd(struct scsi_cmnd *cmd)
> trace_scsi_dispatch_cmd_start(cmd);
> rtn = host->hostt->queuecommand(host, cmd);
> if (rtn) {
> + atomic_dec(&cmd->device->iorequest_cnt);
> trace_scsi_dispatch_cmd_error(cmd, rtn);
> if (rtn != SCSI_MLQUEUE_DEVICE_BUSY &&
> rtn != SCSI_MLQUEUE_TARGET_BUSY)

Looks fine, so the command is accounted in case that it is consumed by
scsi stack, otherwise the counter has to be undone.

Reviewed-by: Ming Lei <[email protected]>


Thanks,
Ming