From mboxrd@z Thu Jan 1 00:00:00 1970 From: Hannes Reinecke Subject: Re: [PATCH] Check return value of fc_block_scsi_eh() Date: Fri, 15 Oct 2010 10:39:21 +0200 Message-ID: <4CB81339.8010105@suse.de> References: <20101013114228.96669354D8@ochil.suse.de> <4CB618A5.8030108@cs.wisc.edu> <4CB6A712.3090705@suse.de> <4CB753D7.6080608@cs.wisc.edu> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Received: from cantor.suse.de ([195.135.220.2]:49831 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751451Ab0JOIjY (ORCPT ); Fri, 15 Oct 2010 04:39:24 -0400 In-Reply-To: <4CB753D7.6080608@cs.wisc.edu> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: Mike Christie Cc: James Bottomley , linux-scsi@vger.kernel.org Mike Christie wrote: > On 10/14/2010 01:45 AM, Hannes Reinecke wrote: >> Mike Christie wrote: >>> On 10/13/2010 06:42 AM, Hannes Reinecke wrote: >>>> >>>> fc_block_scsi_eh() might return with status FAST_IO_FAIL >>>> indicating I/O has been terminated due to fast_io_fail timeout. >>>> In this case the rport is still blocked, so any error recovery >>>> will be failing on this port. >>>> Hence each driver needs to check if the return value from >>>> fc_block_scsi_eh() is something other than SUCCESS, in which >>>> case it should just return with that status. >>>> And we need to update the error handler to deal with a >>>> status of FAST_IO_FAIL, too. >>>> And fc_block_scsi_eh() should return SUCCESS on success, >>>> not 0. Otherwise the calling routine will become confused >>>> when reusing that value. >>>> >>> >>> Is this patch supposed to fix the problem I described or is there m= ore >>> patches to follow or do you think I am being too paranoid? It seems= the >>> patch alone is going to make the problem worse in the drivers you a= re >>> speeding up failure in. In the drivers now checking fc_block_scsi_e= h and >>> returning when fast io fail is returned then the scsi eh >>> scsi_eh_flush_done_q's scsi_finish_command/scsi_queue_insert proces= sing >>> is going to get done faster and more likely to conflict with the >>> termiante_rport_io callback processing, right? >> >> No, this patch does _not_ fix the race you've described, it just >> fixes the problem of fc_block_scsi_eh() returning FAST_IO_FAIL, >> which screws the error handler in drivers not checking the return va= lue. >> So it's partially covered by your patchset. >> >> However, in your patchset you're missing two issues: >> - The current implementation of fc_block_scsi_eh() return '0' on >> success. This screws over drivers which re-uses this value; >> check eg. lpfc_abort_handler(). So we should be returning >> 'SUCCESS' here. >=20 > Yeah, my patchset is actually backwards. I converted the other driver= s > to check for 0 (forgot to fix lpfc though). I think your patch patch > where we return SUCCESS is better than what I was doing. >=20 >=20 >> - scsi_error needs to be fixed up to handle FAST_IO_FAIL. >> Any of the functions called from scsi_abort_eh_cmnd() can return >> FAST_IO_FAIL, in which case escalating to the next function >> becomes pointless. >=20 > There is a problem with fnic (it is also a bug in my patches). If fni= c's > terminate_rport_io fails to abort the cmds, it is relying on the scsi= eh > callouts to clean things up. So if fc_scsi_block_eh returns non-succe= ss > then we cannot return immediately from the callout. The drivers scsi = eh > callout may still need to clean up the command internally. >=20 Maybe it's better to change fnic to modify the FAST_IO_FAIL return value from fc_block_scsi_eh() and return FAILED here. > iSCSI/qla4xxx also needs to be changed to return SUCCESS instead of > zero. Luckily there is only one driver using it so far. >=20 Yes, that would be preferable. >> >> I guess it would make sense to merge these two patchsets, either >> having two patchsets (one for the FAST_IO_FAIL changes and one for >> the rport race) or indeed merge them both into one. >> I'm okay with either of it. >> >=20 > My patches for the race do not work though. When you replied to my > thread I thought you mean you were going to fix that too :) >=20 > I have been thinking of how to fix the race. I will make my patches o= ver > yours since your return SUCCESS fix is better. Ok, I'll be sending an updated patch. Cheers, Hannes --=20 Dr. Hannes Reinecke zSeries & Storage hare@suse.de +49 911 74053 688 SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 N=FCrnberg GF: Markus Rex, HRB 16746 (AG N=FCrnberg) -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" i= n the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html