On Sun, 2011-05-08 at 21:00 +0200, Mikulas Patocka wrote:
> [ the maintainer is not responding, so I'm sending this to other people ]
>
> sym53c8xx_2: avoid data corruption when disk rejects commands with QUEUE
> FULL
Could you describe the corruption, with logs? The behaviour you list
below should may cause disk errors to the filesystem, but it shouldn't
cause corruption.
> When the controller encounters an error (including QUEUE FULL or BUSY
> status), it aborts all not yet submitted requests in the function
> sym_dequeue_from_squeue.
This would be a driver bug: QUEUE_FULL or BUSY should never cause aborts
of outstanding commands.
> This function aborts them with DID_SOFT_ERROR.
>
> If the disk has a full tag queue, the request that caused the overflow is
> aborted with QUEUE FULL status (and the scsi midlayer properly retries it
> until it is accepted by the disk), but other requests are aborted with
> DID_SOFT_ERROR --- for them, the midlayer does just a few retries and then
> signals the error up to sd.
>
> The result is that disk returning QUEUE FULL causes request failures.
>
> The error was reproduced on 53c895 with COMPAQ BD03685A24 disk (rebranded
> ST336607LC) with command queue 48 or 64 tags. The disk has 64 tags, but
> under some access patterns it return QUEUE FULL when there are less than
> 64 pending tags. The SCSI specification allows returning QUEUE FULL
> anytime and it is up to the host to retry.
>
> Signed-off-by: Mikulas Patocka <mpatocka@xxxxxxxxxx>
>
> ---
> drivers/scsi/sym53c8xx_2/sym_hipd.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> Index: linux-2.6.36-rc5-fast/drivers/scsi/sym53c8xx_2/sym_hipd.c
> ===================================================================
> --- linux-2.6.36-rc5-fast.orig/drivers/scsi/sym53c8xx_2/sym_hipd.c 2010-09-27 10:25:59.000000000 +0200
> +++ linux-2.6.36-rc5-fast/drivers/scsi/sym53c8xx_2/sym_hipd.c 2010-09-27 10:26:27.000000000 +0200
> @@ -3000,7 +3000,11 @@ sym_dequeue_from_squeue(struct sym_hcb *
> if ((target == -1 || cp->target == target) &&
> (lun == -1 || cp->lun == lun) &&
> (task == -1 || cp->tag == task)) {
> +#ifdef SYM_OPT_HANDLE_DEVICE_QUEUEING
> sym_set_cam_status(cp->cmd, DID_SOFT_ERROR);
> +#else
> + sym_set_cam_status(cp->cmd, DID_REQUEUE);
> +#endif
This isn't a good idea ... that return code causes retries for ever. I
think the correct fix is just to make the QUEUE_FULL handling in the
driver work.
James
--
To unsubscribe from this list: send the line "unsubscribe linux-scsi" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
