Re: [PATCH] scsi: core: Log SCSI command age with errors

From: Laurence Oberman
Date: Mon Sep 23 2019 - 09:02:42 EST


On Mon, 2019-09-23 at 11:31 +0530, Milan P. Gandhi wrote:
> Couple of users had requested to print the SCSI command age along
> with command failure errors. This is a small change, but allows
> users to get more important information about the command that was
> failed, it would help the users in debugging the command failures:
>
> Signed-off-by: Milan P. Gandhi <mgandhi@xxxxxxxxxx>
> ---
> diff --git a/drivers/scsi/scsi_logging.c
> b/drivers/scsi/scsi_logging.c
> index ecc5918e372a..ca2182bc53c6 100644
> --- a/drivers/scsi/scsi_logging.c
> +++ b/drivers/scsi/scsi_logging.c
> @@ -437,6 +437,7 @@ void scsi_print_result(const struct scsi_cmnd
> *cmd, const char *msg,
> const char *mlret_string = scsi_mlreturn_string(disposition);
> const char *hb_string = scsi_hostbyte_string(cmd->result);
> const char *db_string = scsi_driverbyte_string(cmd->result);
> + unsigned long cmd_age = (jiffies - cmd->jiffies_at_alloc) / HZ;
>
> logbuf = scsi_log_reserve_buffer(&logbuf_len);
> if (!logbuf)
> @@ -478,10 +479,15 @@ void scsi_print_result(const struct scsi_cmnd
> *cmd, const char *msg,
>
> if (db_string)
> off += scnprintf(logbuf + off, logbuf_len - off,
> - "driverbyte=%s", db_string);
> + "driverbyte=%s ", db_string);
> else
> off += scnprintf(logbuf + off, logbuf_len - off,
> - "driverbyte=0x%02x", driver_byte(cmd-
> >result));
> + "driverbyte=0x%02x ",
> + driver_byte(cmd->result));
> +
> + off += scnprintf(logbuf + off, logbuf_len - off,
> + "cmd-age=%lus", cmd_age);
> +
> out_printk:
> dev_printk(KERN_INFO, &cmd->device->sdev_gendev, "%s", logbuf);
> scsi_log_release_buffer(logbuf);
>

This looks to be a useful debug addition to me, and the code looks
correct.
I believe this has also been tested by Milan in our lab.

Reviewed-by: Laurence Oberman <loberman@xxxxxxxxxx>