> -----Original Message-----
> From: Christoph Hellwig [mailto:h...@lst.de]
> Sent: Saturday, 13 September, 2014 6:40 PM
> To: Jens Axboe
> Cc: Elliott, Robert (Server Storage); linux-scsi@vger.kernel.org; linux-
> ker...@vger.kernel.org
> Subject: blk-mq timeout handling fixes
>
> This series fixes various issues with timeout handling that Robert
> ran into when testing scsi-mq heavily. He tested an earlier version,
> and couldn't reproduce the issues anymore, although the series changed
> quite significantly since and should probably be retested.
>
> In summary we not only start the blk-mq timer inside the drivers
> ->queue_rq method after the request has been fully setup, and we
> also tell the drivers if we're timing out a reserved (internal)
> request or a real one. Many drivers including will need to handle
> those internal ones differently, e.g. for scsi-mq we don't even
> have a scsi command structure allocated for the reserved commands.
I have rerun a variety of tests on:
* Jens' for-next tree that went into 3.17rc5
* plus this series
* plus two patches for infinite recursion on flushes from
Ming and then Christoph
and have not been able to trigger the scsi_times_out req->special
NULL pointer dereference that prompted this series.
Testing includes:
* concurrent heavy workload generators:
* fio high iodepth direct 512 byte random reads (> 1M IOPS)
* programs generating large bursts of paged writes
* mkfs.ext4 (followed by e2fsck)
* mkfs.xfs (followed by xfs_check)
* ddpt
* watch -n 0 sync to generate flushes
* scsi_logging_level MLCOMPLETE set to 0 or 1
* scsi_lib.c patched to put all the ACTION_FAIL messages
under level 1 so they can be squelched (massive error
prints cause more timeouts themselves)
* 4 hpsa and 16 mpt3sas devices (all made from SAS SSDs)
* lockless hpsa driver
* injecting errors
* device removal
* device generating infinite errors
* device generating a brief number of errors
The filesystems don't always recover properly, but nothing in
the block or scsi midlayers crashed.
So, you may add this to the series:
Tested-by: Robert Elliott <elli...@hp.com>
---
Rob Elliott HP Server Storage
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