From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.5 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9805BC433E0 for ; Wed, 29 Jul 2020 18:25:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 87F062084D for ; Wed, 29 Jul 2020 18:25:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727008AbgG2SZU (ORCPT ); Wed, 29 Jul 2020 14:25:20 -0400 Received: from netrider.rowland.org ([192.131.102.5]:58697 "HELO netrider.rowland.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1726385AbgG2SZR (ORCPT ); Wed, 29 Jul 2020 14:25:17 -0400 Received: (qmail 1581829 invoked by uid 1000); 29 Jul 2020 14:25:15 -0400 Date: Wed, 29 Jul 2020 14:25:15 -0400 From: Alan Stern To: Martin Kepplinger Cc: James Bottomley , Bart Van Assche , Can Guo , martin.petersen@oracle.com, linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org, kernel@puri.sm Subject: Re: [PATCH] scsi: sd: add runtime pm to open / release Message-ID: <20200729182515.GB1580638@rowland.harvard.edu> References: <20200706164135.GE704149@rowland.harvard.edu> <20200728200243.GA1511887@rowland.harvard.edu> <20200729143213.GC1530967@rowland.harvard.edu> <1596033995.4356.15.camel@linux.ibm.com> <1596034432.4356.19.camel@HansenPartnership.com> <1596037482.4356.37.camel@HansenPartnership.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-scsi-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-scsi@vger.kernel.org On Wed, Jul 29, 2020 at 06:43:48PM +0200, Martin Kepplinger wrote: > > > Am 29. Juli 2020 17:44:42 MESZ schrieb James Bottomley : > >On Wed, 2020-07-29 at 17:40 +0200, Martin Kepplinger wrote: > >> On 29.07.20 16:53, James Bottomley wrote: > >> > On Wed, 2020-07-29 at 07:46 -0700, James Bottomley wrote: > >> > > On Wed, 2020-07-29 at 10:32 -0400, Alan Stern wrote: > >[...] > >> > > > This error report comes from the SCSI layer, not the block > >> > > > layer. > >> > > > >> > > That sense code means "NOT READY TO READY CHANGE, MEDIUM MAY HAVE > >> > > CHANGED" so it sounds like it something we should be > >> > > ignoring. Usually this signals a problem, like you changed the > >> > > medium manually (ejected the CD). But in this case you can tell > >> > > us to expect this by setting > >> > > > >> > > sdev->expecting_cc_ua > >> > > > >> > > And we'll retry. I think you need to set this on all resumed > >> > > devices. > >> > > >> > Actually, it's not quite that easy, we filter out this ASC/ASCQ > >> > combination from the check because we should never ignore medium > >> > might have changed events on running devices. We could ignore it > >> > if we had a flag to say the power has been yanked (perhaps an > >> > additional sdev flag you set on resume) but we would still miss the > >> > case where you really had powered off the drive and then changed > >> > the media ... if you can regard this as the user's problem, then we > >> > might have a solution. > >> > > >> > James > >> > > >> > >> oh I see what you mean now, thanks for the ellaboration. > >> > >> if I do the following change, things all look normal and runtime pm > >> works. I'm not 100% sure if just setting expecting_cc_ua in resume() > >> is "correct" but that looks like it is what you're talking about: > >> > >> (note that this is of course with the one block layer diff applied > >> that Alan posted a few emails back) > >> > >> > >> --- a/drivers/scsi/scsi_error.c > >> +++ b/drivers/scsi/scsi_error.c > >> @@ -554,16 +554,8 @@ int scsi_check_sense(struct scsi_cmnd *scmd) > >> * so that we can deal with it there. > >> */ > >> if (scmd->device->expecting_cc_ua) { > >> - /* > >> - * Because some device does not queue unit > >> - * attentions correctly, we carefully check > >> - * additional sense code and qualifier so as > >> - * not to squash media change unit attention. > >> - */ > >> - if (sshdr.asc != 0x28 || sshdr.ascq != 0x00) > >> { > >> - scmd->device->expecting_cc_ua = 0; > >> - return NEEDS_RETRY; > >> - } > >> + scmd->device->expecting_cc_ua = 0; > >> + return NEEDS_RETRY; > > > >Well, yes, but you can't do this because it would lose us media change > >events in the non-suspend/resume case which we really don't want. > >That's why I was suggesting a new flag. > > > >James > > also if I set expecting_cc_ua in resume() only, like I did? That wouldn't make any difference. The information sent by your card reader has sshdr.asc == 0x28 and sshdr.ascq == 0x00 (you can see it in the log). So because of the code here in scsi_check_sense(), which you can't change, the Unit Attention sent by the card reader would not be retried even if you do set the flag in resume(). Alan Stern