From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Stewart, Sean" Subject: Re: [PATCH] scsi_dh_alua: Requeue another not ready check condition at ML Date: Fri, 28 Feb 2014 20:20:28 +0000 Message-ID: <1393618828.13153.11.camel@ict-vth-stewarts01.ict.englab.netapp.com> References: <8255ED565A0EAA4A960625E27D49DBF24AC8B21D@SACEXCMBX04-PRD.hq.netapp.com> <530FED5B.60803@cs.wisc.edu> <5310A7EF.7060902@suse.de> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 8BIT Return-path: Received: from mx11.netapp.com ([216.240.18.76]:16381 "EHLO mx11.netapp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752043AbaB1UUe convert rfc822-to-8bit (ORCPT ); Fri, 28 Feb 2014 15:20:34 -0500 In-Reply-To: <5310A7EF.7060902@suse.de> Content-Language: en-US Content-ID: <754D48FDA100764E965C4DDF38564A20@hq.netapp.com> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: Hannes Reinecke Cc: Mike Christie , "Stewart, Sean" , "linux-scsi@vger.kernel.org" , "dm-devel@redhat.com" , "James.Bottomley@HansenPartnership.com" On Fri, 2014-02-28 at 16:14 +0100, Hannes Reinecke wrote: > On 02/28/2014 02:58 AM, Mike Christie wrote: > > On 02/27/2014 06:14 PM, Stewart, Sean wrote: > >> This allows the sd driver to retry commands like read capacity until a > >> LUN is ready, rather than giving up after three retries. > >> > >> In NetApp E-Series, a controller can return not ready like this when it > >> quiesces I/O on the controller that just came on the network, during a > >> firmware upgrade procedure, and retrying the command at the midlayer > >> will allow the discovery to complete, successfully. > >> > >> Signed-off-by: Sean Stewart > >> --- > >> drivers/scsi/device_handler/scsi_dh_alua.c | 5 +++++ > >> 1 file changed, 5 insertions(+) > >> > >> diff --git a/drivers/scsi/device_handler/scsi_dh_alua.c b/drivers/scsi/device_handler/scsi_dh_alua.c > >> index 5248c88..95d87fe 100644 > >> --- a/drivers/scsi/device_handler/scsi_dh_alua.c > >> +++ b/drivers/scsi/device_handler/scsi_dh_alua.c > >> @@ -454,6 +454,11 @@ static int alua_check_sense(struct scsi_device *sdev, > >> { > >> switch (sense_hdr->sense_key) { > >> case NOT_READY: > >> + if (sense_hdr->asc == 0x04 && sense_hdr->ascq == 0x01) > >> + /* > >> + * LUN Not Ready -- In process of becoming ready > >> + */ > >> + return ADD_TO_MLQUEUE; > > > > It seems like the check_sense callout is being used to work around > > scsi-ml in a lot of the additions that are not alua specific. If this is > > meant for a specific target then it should not be here. If this is > > non-alua specific behavior then it should also not be here either. This sounds reasonable to me. Originally, our target would return a vendor-specific check condition, and I knew we wouldn't be able to get the alua handler to retry that. I also saw if we could get this condition to return 02/04/0A so we'd be covered, but it wouldn't accurately describe what's going on, so we set the target to return 02/04/01. In any case, without having the device handler do ADD_TO_MLQUEUE, I see the command come back with the check condition, return SUCCESS, then the read_capacity_10 function burns through it's three retries: int retries = 3, reset_retries = READ_CAPACITY_RETRIES_ON_RESET; I captured this with scsi midlayer debugging to show what's going on. Feb 28 13:51:44 wica-fo-stone kernel: sd 2:0:2:0: Send: 0xffff880420259cc0 Feb 28 13:51:44 wica-fo-stone kernel: sd 2:0:2:0: CDB: Read Capacity(10): 25 00 00 00 00 00 00 00 00 00 Feb 28 13:51:45 wica-fo-stone kernel: sd 2:0:2:0: Done: 0xffff880420259cc0 SUCCESS The same scsi_cmnd comes back with SUCCESS twice more, then: Feb 28 13:51:46 wica-fo-stone kernel: sd 2:0:2:0: [sdd] READ CAPACITY failed > > > > If the IO was not a REQ_TYPE_BLOCK_PC request, then it would retried by > > scsi_io_completion. Same with the other ones like inquiry data changed, > > report luns data changed, etc. > > > > Are we sure we don't want to fix the REQ_TYPE_BLOCK_PC/scsi_execute* > > users to retry, or to add some new flag that those users can use that > > tells scsi-ml to retry like it normally would so callers do not have to > > check for all these errors, or just add these to scsi_decide_disposition? > > > Yes, that's definitely a better idea. I've stumbled across this > issue several times now. Same.. This actually seems to have come up a lot. We had basically the same problem when we have a new VID/PID, but a customer uses an OS without the VID/PID in the RDAC handler. It can cause a lot of headaches. I think it should be possible for us to approach this in such a way that a transient state on the target won't render the SCSI disk unusable (as is done here). So, by a flag, do you mean we could add something to the request flags field? We could use this to signify a command that should keep retrying in the way that I'm looking for here (commands related to initial discovery, like read capacities, are what I'm thinking of). Thanks, Sean