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From: James Bottomley <James.Bottomley@HansenPartnership.com>
To: Martin Kepplinger <martin.kepplinger@puri.sm>,
	Alan Stern <stern@rowland.harvard.edu>
Cc: Bart Van Assche <bvanassche@acm.org>,
	Can Guo <cang@codeaurora.org>,
	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
Date: Wed, 29 Jul 2020 08:44:42 -0700
Message-ID: <1596037482.4356.37.camel@HansenPartnership.com> (raw)
In-Reply-To: <d9bb92e9-23fa-306f-c7f2-71a81ab28811@puri.sm>

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


  reply index

Thread overview: 68+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-23 11:10 Martin Kepplinger
2020-06-24 13:33 ` Bart Van Assche
2020-06-25  8:16   ` Martin Kepplinger
2020-06-25 14:52     ` Alan Stern
2020-06-26  3:53     ` Bart Van Assche
2020-06-26 15:07     ` Bart Van Assche
2020-06-26 15:44       ` Alan Stern
2020-06-28  2:37         ` Bart Van Assche
2020-06-28 13:10           ` Alan Stern
2020-06-29  9:42         ` Martin Kepplinger
2020-06-29 16:15           ` Alan Stern
2020-06-29 16:56             ` Bart Van Assche
2020-06-29 17:40               ` Alan Stern
2020-06-30  3:33             ` Martin Kepplinger
2020-06-30 13:38               ` Alan Stern
2020-06-30 15:59             ` Bart Van Assche
2020-06-30 18:02               ` Alan Stern
2020-06-30 19:23                 ` Bart Van Assche
2020-06-30 19:38                   ` Alan Stern
2020-06-30 23:31                     ` Bart Van Assche
2020-07-01  0:49                       ` Alan Stern
2020-07-06 16:41                         ` Alan Stern
2020-07-28  7:02                           ` Martin Kepplinger
2020-07-28 20:02                             ` Alan Stern
2020-07-29 14:12                               ` Martin Kepplinger
2020-07-29 14:32                                 ` Alan Stern
2020-07-29 14:44                                   ` Martin K. Petersen
2020-07-29 14:56                                     ` Alan Stern
2020-07-29 14:46                                   ` James Bottomley
2020-07-29 14:53                                     ` James Bottomley
2020-07-29 15:40                                       ` Martin Kepplinger
2020-07-29 15:44                                         ` James Bottomley [this message]
2020-07-29 16:43                                           ` Martin Kepplinger
2020-07-29 18:25                                             ` Alan Stern
2020-07-29 18:29                                               ` James Bottomley
2020-07-30  8:52                                                 ` Martin Kepplinger
2020-07-30  8:54                                                   ` Martin Kepplinger
2020-07-30 15:10                                                   ` Alan Stern
2020-08-04  9:39                                                     ` Martin Kepplinger
2020-08-07  9:51                                                       ` Martin Kepplinger
2020-08-07 14:30                                                         ` Alan Stern
2020-08-08  6:59                                                           ` Martin Kepplinger
2020-08-08 15:05                                                             ` Alan Stern
2020-08-09  9:20                                                               ` Martin Kepplinger
2020-08-09 15:26                                                                 ` Alan Stern
2020-08-10 12:03                                                                   ` Martin Kepplinger
2020-08-10 14:13                                                                     ` Alan Stern
2020-08-11  7:55                                                                       ` Martin Kepplinger
2020-08-11 13:48                                                                         ` Alan Stern
2020-08-23 14:57                                                                         ` [PATCH] block: Fix bug in runtime-resume handling Alan Stern
2020-08-24 17:48                                                                           ` Bart Van Assche
2020-08-24 20:13                                                                             ` Alan Stern
2020-08-26  7:48                                                                               ` Martin Kepplinger
2020-08-27 17:42                                                                                 ` Martin Kepplinger
2020-08-27 20:29                                                                                   ` Alan Stern
2020-08-29  7:24                                                                                     ` Martin Kepplinger
2020-08-29 15:26                                                                                       ` Alan Stern
2020-08-29 16:33                                                                                         ` Martin Kepplinger
2020-08-29 18:56                                                                                           ` Alan Stern
2020-08-30  0:38                                                                                             ` Bart Van Assche
2020-08-30  1:06                                                                                               ` Alan Stern
2020-07-29 15:40                                       ` [PATCH] scsi: sd: add runtime pm to open / release Alan Stern
2020-07-29 15:49                                         ` James Bottomley
2020-07-29 16:17                                           ` Alan Stern
2020-07-29 15:52                                         ` Martin Kepplinger
2020-07-29 18:10                                   ` Douglas Gilbert
2020-07-30  8:05             ` Martin Kepplinger
2020-07-30 15:14               ` Alan Stern

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