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

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Message-ID: <20100601142822.GW9453@laptop>
Date:	Wed, 2 Jun 2010 00:28:22 +1000
From:	Nick Piggin <npiggin@...e.de>
To:	"Martin K. Petersen" <martin.petersen@...cle.com>
Cc:	James Bottomley <James.Bottomley@...e.de>,
	Chris Mason <chris.mason@...cle.com>,
	Christof Schmitt <christof.schmitt@...ibm.com>,
	Boaz Harrosh <bharrosh@...asas.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 09:50:29AM -0400, Martin K. Petersen wrote:
> >>>>> "James" == James Bottomley <James.Bottomley@...e.de> writes:
> 
> James> Would it be too much work in the fs to mark the page dirty before
> James> you begin altering it (and again after you finish, just in case
> James> some cleaner noticed and initiated a write)?  Or some other flag
> James> that indicates page under modification?  All the process
> James> controlling the writeout (which is pretty high up in the stack)
> James> needs to know is if we triggered the check error by altering the
> James> page while it was in flight.
> 
> James> I agree that a block based retry would close all the holes ... it
> James> just doesn't look elegant to me that the fs will already be
> James> repeating the I/O if it changed the page and so will block.
> 
> I experimented with this approach a while back.  However, I quickly got
> into a situation where frequently updated blocks never made it to disk
> because the page was constantly being updated.  And all writes failed
> with a guard tag error.

What if you bounce in the case of a first guard error?

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