linux-ext4 - Re: [PATCH RFC] ext3 data=guarded v3

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Message-Id: <1239906340.6091.5.camel@marge.simson.net>
Date:	Thu, 16 Apr 2009 20:25:40 +0200
From:	Mike Galbraith <efault@....de>
To:	Chris Mason <chris.mason@...cle.com>
Cc:	Jan Kara <jack@...e.cz>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Theodore Ts'o <tytso@....edu>,
	Linux Kernel Developers List <linux-kernel@...r.kernel.org>,
	Ext4 Developers List <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH RFC] ext3 data=guarded v3

On Thu, 2009-04-16 at 13:12 -0400, Chris Mason wrote:
> On Thu, 2009-04-16 at 10:56 -0400, Chris Mason wrote:
> > On Thu, 2009-04-16 at 13:39 +0200, Mike Galbraith wrote:
> > > On Wed, 2009-04-15 at 13:22 -0400, Chris Mason wrote:
> > > > Hello everyone,
> > > 
> > > Greetings,
> > > 
> > > > This passed a longer stress test and generally seems to be working.  I
> > > > don't think anyone would recommend it as a default for 2.6.30, but it
> > > > may be a good idea to have a review party and decide if it is safe enough
> > > > to include so people can experiment with it.
> > > 
> > > I know you didn't say RFT, but I did some anyway, and found a 100%
> > > repeatable corruption scenario wrt git+umount.
> > > 
> > 
> > Well, that's a surprise.  I can trigger it here too, trying to figure
> > out how this is different from the fsx and fsstress hammering.  It looks
> > like git is just going good old fashioned writes, so I must be losing
> > one or two of them.
> 
> Ah ok, it is just a missed i_size update.  Basically because file_write
> doesn't wait for page writeback to finish, someone can be updating
> i_size at the same time the end_io handler for the last page is running.
> 
> Git triggers this when it does the sha1flush just before closing the
> file.

A brief note (preferably with 8x10 color glossies with circles and
arrows) on how you figured that out so quick would be a good LKML
archive investment :)

	-Mike

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