Re: [PATCH] scsi: sd: add runtime pm to open / release

Martin Kepplinger
2020-08-04T09:40:40Z

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