linux-kernel - Re: [PATCH] sd: do not set changed flag on all unit attention conditions

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Date:	Mon, 16 Jul 2012 19:20:22 +0200
From:	Paolo Bonzini <pbonzini@...hat.com>
To:	James Bottomley <James.Bottomley@...senPartnership.com>
CC:	linux-kernel@...r.kernel.org, linux-scsi@...r.kernel.org
Subject: Re: [PATCH] sd: do not set changed flag on all unit attention conditions

Il 16/07/2012 18:18, James Bottomley ha scritto:
>> > diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
>> > index b583277..6d8ca08 100644
>> > --- a/drivers/scsi/scsi_lib.c
>> > +++ b/drivers/scsi/scsi_lib.c
>> > @@ -843,8 +843,11 @@ void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes)
>> >  	} else if (sense_valid && !sense_deferred) {
>> >  		switch (sshdr.sense_key) {
>> >  		case UNIT_ATTENTION:
>> > -			if (cmd->device->removable) {
>> > -				/* Detected disc change.  Set a bit
>> > +			if (cmd->device->removable &&
>> > +			    (sshdr.asc == 0x3a ||
>> > +			     (sshdr.asc == 0x28 && sshdr.ascq == 0x00))) {
>> > +				/* "No medium" or "Medium may have changed."
>> > +				 * This means a disc change.  Set a bit
> This type of change would likely cause a huge cascade of errors in real
> removable media devices.  Under the MMC standards, which a lot of the
> older removable discs seem to follow, UNIT ATTENTION indicates either
> medium change or device reset (which we check for and eat lower down);
> we can't rely on them giving proper SBC-2 sense codes.  If you want to
> pretend to be removable media, you have to conform to its standards.

Would you accept a patch doing the opposite, i.e. passing some sense
codes such as PARAMETERS CHANGED and TARGET OPERATING CONDITIONS HAVE
CHANGED?

Paolo
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