linux-kernel - Re: scsi_error: do not allow IO errors with certain ILLEGAL

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Message-ID: <yq1d39iipra.fsf@sermon.lab.mkp.net>
Date:	Mon, 13 Feb 2012 12:53:29 -0500
From:	"Martin K. Petersen" <martin.petersen@...cle.com>
To:	Mike Snitzer <snitzer@...hat.com>
Cc:	"Martin K. Petersen" <martin.petersen@...cle.com>,
	linux-scsi@...r.kernel.org,
	James Bottomley <jbottomley@...allels.com>,
	Hannes Reinecke <hare@...e.de>, linux-kernel@...r.kernel.org
Subject: Re: scsi_error: do not allow IO errors with certain ILLEGAL_REQUEST sense to be retryable

>>>>> "Mike" == Mike Snitzer <snitzer@...hat.com> writes:

Mike> So that makes 3 different _prominent_ storage vendors, that I am
Mike> aware of, that are bitten by their broken storage (relative to
Mike> discard and properly advertising which variant they actually
Mike> support).  I'd much rather deal with the storage vendors (or their
Mike> customers) reporting that discards aren't working than mutual
Mike> customers reporting that they cannot even install to the storage.

More graceful handling of the sense data aside, we do have a couple of
options:

 1. Now that the provisioning portion seems to be stable in SBC-3 we can
    nuke the interim spec heuristics and only support devices that
    report the right thing. This may disable provisioning for some
    existing users whose arrays run non-compliant firmware.

 2. We can add another layer of heuristics based on the RSOC wrapper I
    introduced for write same. Maybe you could send me sg_opcodes output
    for the arrays in question?

Mike> The ultimate fix is clear: storage vendors need to fix their
Mike> storage (2 of the 3 have, 1 is working on it).  But a Linux-only
Mike> workaround for this series of unfortunate events (particularly as
Mike> it happens with multipath in the mix) is to have SCSI classify
Mike> certain ILLEGAL_REQUEST as the TARGET_ERROR that they are.

I don't have a fundamental problem with your patch. But since we
explicitly handle ILLEGAL REQUEST with 0x20 and 0x24 in sd.c I wonder
what's broken? We should disable discard support if the WRITE SAME w/
UNMAP fails.

I'll see if I can figure out what's going on unless you beat me to it...

-- 
Martin K. Petersen	Oracle Linux Engineering
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