Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752596Ab1EILHk (ORCPT ); Mon, 9 May 2011 07:07:40 -0400 Received: from artax.karlin.mff.cuni.cz ([195.113.26.195]:52861 "EHLO artax.karlin.mff.cuni.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752477Ab1EILHj (ORCPT ); Mon, 9 May 2011 07:07:39 -0400 Date: Mon, 9 May 2011 13:07:38 +0200 (CEST) From: Mikulas Patocka To: James Bottomley cc: Matthew Wilcox , linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] sym53c8xx_2: avoid data corruption when disk rejects commands with QUEUE FULL In-Reply-To: <1304886595.4865.3.camel@mulgrave.site> Message-ID: References: <1304886595.4865.3.camel@mulgrave.site> User-Agent: Alpine 2.00 (DEB 1167 2008-08-23) X-Personality-Disorder: Schizoid MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3678 Lines: 91 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 > > > > --- > > 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/