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

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Date:	Thu, 16 Apr 2009 13:12:56 -0400
From:	Chris Mason <chris.mason@...cle.com>
To:	Mike Galbraith <efault@....de>
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 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.

I'm testing the fixes here, will resend in a little bit.

Thanks!

-chris


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