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From: Martin Kepplinger <martin.kepplinger@puri.sm>
To: Alan Stern <stern@rowland.harvard.edu>
Cc: James Bottomley <James.Bottomley@hansenpartnership.com>,
	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: Fri, 7 Aug 2020 11:51:21 +0200
Message-ID: <425990b3-4b0b-4dcf-24dc-4e7e60d5869d@puri.sm> (raw)
In-Reply-To: <9b80ca7c-39f8-e52d-2535-8b0baf93c7d1@puri.sm>

On 04.08.20 11:39, Martin Kepplinger wrote:
> On 30.07.20 17:10, Alan Stern wrote:
>> On Thu, Jul 30, 2020 at 10:52:14AM +0200, Martin Kepplinger wrote:
>>> Maybe I should just start a new discussion with a patch, but the below
>>> is what makes sense to me (when I understand you correctly) and seems to
>>> work. I basically add a new flag, so that the old flags behave unchanged
>>> and only call it during *runtime* resume for SD cards:
>>>
>>>
>>> --- a/drivers/scsi/scsi_error.c
>>> +++ b/drivers/scsi/scsi_error.c
>>> @@ -553,15 +553,21 @@ int scsi_check_sense(struct scsi_cmnd *scmd)
>>>                  * information that we should pass up to the upper-level
>>> driver
>>>                  * so that we can deal with it there.
>>>                  */
>>> -               if (scmd->device->expecting_cc_ua) {
>>> +               if (scmd->device->expecting_cc_ua ||
>>> +                   scmd->device->expecting_media_change) {
>>>                         /*
>>>                          * 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.
>>> +                        * not to squash media change unit attention;
>>> +                        * unless expecting_media_change is set, indicating
>>> +                        * that the media (most likely) didn't change
>>> +                        * but a device only believes so (for example
>>> +                        * because of suspend/resume).
>>>                          */
>>> -                       if (sshdr.asc != 0x28 || sshdr.ascq != 0x00) {
>>> -                               scmd->device->expecting_cc_ua = 0;
>>> +                       if ((sshdr.asc != 0x28 || sshdr.ascq != 0x00) ||
>>> +                           scmd->device->expecting_media_change) {
>>> +                               scmd->device->expecting_media_change = 0;
>>>                                 return NEEDS_RETRY;
>>>                         }
>>>                 }
>>> diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
>>> index d90fefffe31b..b647fab2b663 100644
>>> --- a/drivers/scsi/sd.c
>>> +++ b/drivers/scsi/sd.c
>>> @@ -114,6 +114,7 @@ static void sd_shutdown(struct device *);
>>>  static int sd_suspend_system(struct device *);
>>>  static int sd_suspend_runtime(struct device *);
>>>  static int sd_resume(struct device *);
>>> +static int sd_resume_runtime(struct device *);
>>>  static void sd_rescan(struct device *);
>>>  static blk_status_t sd_init_command(struct scsi_cmnd *SCpnt);
>>>  static void sd_uninit_command(struct scsi_cmnd *SCpnt);
>>> @@ -574,7 +575,7 @@ static const struct dev_pm_ops sd_pm_ops = {
>>>         .poweroff               = sd_suspend_system,
>>>         .restore                = sd_resume,
>>>         .runtime_suspend        = sd_suspend_runtime,
>>> -       .runtime_resume         = sd_resume,
>>> +       .runtime_resume         = sd_resume_runtime,
>>>  };
>>>
>>>  static struct scsi_driver sd_template = {
>>> @@ -3652,6 +3653,21 @@ static int sd_resume(struct device *dev)
>>>         return ret;
>>>  }
>>>
>>> +static int sd_resume_runtime(struct device *dev)
>>> +{
>>> +       struct scsi_disk *sdkp = dev_get_drvdata(dev);
>>> +
>>> +       /* Some SD cardreaders report media change when resuming from
>>> suspend
>>> +        * because they can't keep track during suspend. */
>>> +
>>> +       /* XXX This is not unproblematic though: We won't notice when a card
>>> +        * was really changed during runtime suspend! We basically rely
>>> on users
>>> +        * to unmount or suspend before doing so. */
>>> +       sdkp->device->expecting_media_change = 1;
>>> +
>>> +       return sd_resume(dev);
>>> +}
>>> +
>>>  /**
>>>   *     init_sd - entry point for this driver (both when built in or when
>>>   *     a module).
>>> diff --git a/include/scsi/scsi_device.h b/include/scsi/scsi_device.h
>>> index bc5909033d13..8c8f053f71c8 100644
>>> --- a/include/scsi/scsi_device.h
>>> +++ b/include/scsi/scsi_device.h
>>> @@ -169,6 +169,8 @@ struct scsi_device {
>>>                                  * this device */
>>>         unsigned expecting_cc_ua:1; /* Expecting a CHECK_CONDITION/UNIT_ATTN
>>>                                      * because we did a bus reset. */
>>> +       unsigned expecting_media_change:1; /* Expecting media change
>>> ASC/ASCQ
>>> +                                             when it actually doesn't
>>> change */
>>>         unsigned use_10_for_rw:1; /* first try 10-byte read / write */
>>>         unsigned use_10_for_ms:1; /* first try 10-byte mode sense/select */
>>>         unsigned set_dbd_for_ms:1; /* Set "DBD" field in mode sense */
>>
>> That's pretty much what James was suggesting, except for one thing: You 
>> must not set sdkp->device->expecting_media_change to 1 for all devices 
>> in sd_runtime_resume().  Only for devices which may generate a spurious 
>> Unit Attention following runtime resume -- and maybe not even for all of 
>> them, depending on what the user wants.
>>
>> Alan Stern
>>
> 
> when I mount the SD card myself or via Nautilus, things work. When I put
> sth like:
> 
> /dev/sda1 /mnt/sda1 auto auto,nofail 0 2
> 
> into fstab, I *still* get (constantly) when accessing the files:
> 
> [   50.838061] sd 0:0:0:0: [sda] tag#0 device offline or changed
> 
> why could that be? is there another place we would add such a new flag
> (not only resume())?
> 
>                               martin
> 


it's really strange: below is the change I'm trying. Of course that's
only for testing the functionality, nothing how a patch could look like.

While I remember it had worked, now (weirdly since I tried that mounting
via fstab) it doesn't anymore!

What I understand (not much): I handle the error with "retry" via the
new flag, but scsi_decide_disposition() returns SUCCESS because of "no
more retries"; but it's the first and only time it's called.

How can this be? What am I missing?



--- a/drivers/scsi/scsi_error.c
+++ b/drivers/scsi/scsi_error.c
@@ -565,6 +565,13 @@ int scsi_check_sense(struct scsi_cmnd *scmd)
 				return NEEDS_RETRY;
 			}
 		}
+		if (scmd->device->expecting_media_change) {
+			if (sshdr.asc == 0x28 && sshdr.ascq == 0x00) {
+				scmd->device->expecting_media_change = 0;
+				return NEEDS_RETRY;
+			}
+		}
+
 		/*
 		 * we might also expect a cc/ua if another LUN on the target
 		 * reported a UA with an ASC/ASCQ of 3F 0E -
diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index d90fefffe31b..bb583e403b81 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -3642,6 +3642,8 @@ static int sd_resume(struct device *dev)
 	if (!sdkp)	/* E.g.: runtime resume at the start of sd_probe() */
 		return 0;

+	sdkp->device->expecting_media_change = 1;
+
 	if (!sdkp->device->manage_start_stop)
 		return 0;

diff --git a/include/scsi/scsi_device.h b/include/scsi/scsi_device.h
index bc5909033d13..f5fc1af68e00 100644
--- a/include/scsi/scsi_device.h
+++ b/include/scsi/scsi_device.h
@@ -169,6 +169,7 @@ struct scsi_device {
 				 * this device */
 	unsigned expecting_cc_ua:1; /* Expecting a CHECK_CONDITION/UNIT_ATTN
 				     * because we did a bus reset. */
+	unsigned expecting_media_change:1;
 	unsigned use_10_for_rw:1; /* first try 10-byte read / write */
 	unsigned use_10_for_ms:1; /* first try 10-byte mode sense/select */
 	unsigned set_dbd_for_ms:1; /* Set "DBD" field in mode sense */

  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
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 [this message]
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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