Re: [Patch] scsi_error: should not get sense for timeout IO in scsi error handler

[Hannes Reinecke <hare@suse.de>]

On 07/31/2015 11:52 AM, jiang.biao2@zte.com.cn wrote:
> scsi_error: should not get sense for timeout IO in scsi error handler
> 
> When an IO timeout occurs, the IO will be aborted in
> scsi_abort_command() and SCSI_EH_ABORT_SCHEDULED will be set. Because
> of that, the SCSI_EH_CANCEL_CMD will be clear in scsi_eh_scmd_add().
> So when scsi error handler starts, it will get sense for this
> timeout IO and the scmd of the IO request will be reused. In that
> case, the scmd may be double released when racing with io_done(),
> which will result in crash.
> SO SCSI_EH_ABORT_SCHEDULED should also be checked when getting sense.
> The bug maybe reproduced when the link between host and disk is
> unstable.
> 
> Signed-off-by: Jiang Biao <jiang.biao2@zte.com.cn>
> Signed-off-by: Long Chun <long.chun@zte.com.cn>
> Reviewed-by: Tan Hu <tan.hu@zte.com.cn>
> Reviewed-by: Chen Donghai <chen.donghai@zte.com.cn>
> Reviewed-by: Cai Qu <cai.qu@zte.com.cn>
> 
> diff -uprN drivers/scsi/scsi_error.c drivers_new/scsi/scsi_error.c
> --- scsi/scsi_error.c   2015-07-31 16:03:18.000000000 +0800
> +++ scsi_new/scsi_error.c       2015-07-31 16:29:25.000000000 +0800
> @@ -1156,9 +1156,14 @@ int scsi_eh_get_sense(struct list_head *
>         struct Scsi_Host *shost;
>         int rtn;
> 
> +       /*
> +        * If SCSI_EH_ABORT_SCHEDULED has been set, it is timeout IO,
> +        * should not get sense.
> +        */
>         list_for_each_entry_safe(scmd, next, work_q, eh_entry) {
>                 if ((scmd->eh_eflags & SCSI_EH_CANCEL_CMD) ||
> -                   SCSI_SENSE_VALID(scmd))
> +                   (scmd->eh_eflags & SCSI_EH_ABORT_SCHEDULED) ||
> +                    SCSI_SENSE_VALID(scmd))
>                         continue;
> 
>                 shost = scmd->device->host;
> --
_Actually_ you need to test for both, SCSI_EH_CANCEL_CMD _and_
SCSI_EH_ABORT_SCHEDULED.
Not every driver is required to implement and/or support
asynchronous command aborts, and those will be setting
SCSI_EH_CANCEL_CMD even though they've run into a timeout.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		               zSeries & Storage
hare@suse.de			               +49 911 74053 688
SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: F. Imendörffer, J. Smithard, J. Guild, D. Upmanyu, G. Norton
HRB 21284 (AG Nürnberg)
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