linux-kernel - Re: Wrong DIF guard tag on ext2 write

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Message-ID: <yq1iq64kv9f.fsf@sermon.lab.mkp.net>
Date:	Mon, 31 May 2010 10:20:44 -0400
From:	"Martin K. Petersen" <martin.petersen@...cle.com>
To:	Christof Schmitt <christof.schmitt@...ibm.com>
Cc:	linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-fsdevel@...r.kernel.org
Subject: Re: Wrong DIF guard tag on ext2 write

>>>>> "Christof" == Christof Schmitt <christof.schmitt@...ibm.com> writes:

Christof> Since the guard tags are created in Linux, it seems that the
Christof> data attached to the write request changes between the
Christof> generation in bio_integrity_generate and the call to
Christof> sd_prep_fn.

Yep, known bug.  Page writeback locking is messed up for buffer_head
users.  The extNfs folks volunteered to look into this a while back but
I don't think they have found the time yet.

Christof> Using ext3 or ext4 instead of ext2 does not show the problem.

Last I looked there were still code paths in ext3 and ext4 that
permitted pages to be changed during flight.  I guess you've just been
lucky.

-- 
Martin K. Petersen	Oracle Linux Engineering
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