Messages in this thread | | | Date | Mon, 9 May 2011 13:07:38 +0200 (CEST) | From | Mikulas Patocka <> | Subject | Re: [PATCH] sym53c8xx_2: avoid data corruption when disk rejects commands with QUEUE FULL |
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On Sun, 8 May 2011, James Bottomley wrote:
> 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?
sd 0:0:0:0: [sda] Unhandled error code sd 0:0:0:0: [sda] Result: hostbyte=DID_SOFT_ERROR driverbyte=DRIVER_OK sd 0:0:0:0: [sda] CDB: Write(10): 2a 00 00 01 37 9a 00 00 02 00 lost page write due to I/O error on sda1 sd 0:0:0:0: [sda] Unhandled error code sd 0:0:0:0: [sda] Result: hostbyte=DID_SOFT_ERROR driverbyte=DRIVER_OK sd 0:0:0:0: [sda] CDB: Write(10): 2a 00 00 01 38 10 00 00 10 00 lost page write due to I/O error on sda1 ...
> The behaviour you list below should may cause disk errors to the > filesystem, but it shouldn't cause corruption.
It causes disk write errors, and in most filesystems, write errors result in data corruption --- i.e. some metadata are written, other metadata aren't, and the result is a corrupted filesystem.
> > 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.
Yes, it is a driver bug.
> > 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@redhat.com> > > > > --- > > 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.
If the disk returns QUEUE_FULL, we should retry forever.
> I think the correct fix is just to make the QUEUE_FULL handling in the > driver work.
When I enabled SYM_OPT_HANDLE_DEVICE_QUEUEING, I got crashes.
> James
Mikulas
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