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

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Message-ID: <20100601133341.GK8980@think>
Date:	Tue, 1 Jun 2010 09:33:41 -0400
From:	Chris Mason <chris.mason@...cle.com>
To:	James Bottomley <James.Bottomley@...e.de>
Cc:	Christof Schmitt <christof.schmitt@...ibm.com>,
	Boaz Harrosh <bharrosh@...asas.com>,
	"Martin K. Petersen" <martin.petersen@...cle.com>,
	linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-fsdevel@...r.kernel.org
Subject: Re: Wrong DIF guard tag on ext2 write

On Tue, Jun 01, 2010 at 01:27:56PM +0000, James Bottomley wrote:
> On Tue, 2010-06-01 at 12:30 +0200, Christof Schmitt wrote:
> > What is the best strategy to continue with the invalid guard tags on
> > write requests? Should this be fixed in the filesystems?
> 
> For write requests, as long as the page dirty bit is still set, it's
> safe to drop the request, since it's already going to be repeated.  What
> we probably want is an error code we can return that the layer that sees
> both the request and the page flags can make the call.

I'm afraid this isn't entirely true.  The FS tends to do this:

change the page
<---------> truck sized race right here where the page is clean
mark the page dirty

-chris
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