linux-kernel - Re: Apparent serious progressive ext4 data corruption bug in 3.6.3 (and other stable branches?)

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Date:	Sun, 28 Oct 2012 21:35:58 -0500
From:	Eric Sandeen <sandeen@...hat.com>
To:	"Theodore Ts'o" <tytso@....edu>, Nix <nix@...eri.org.uk>,
	linux-ext4@...r.kernel.org, linux-kernel@...r.kernel.org,
	gregkh@...uxfoundation.org
Subject: Re: Apparent serious progressive ext4 data corruption bug in 3.6.3
 (and other stable branches?)

On 10/28/12 9:34 PM, Theodore Ts'o wrote:
> On Sun, Oct 28, 2012 at 09:24:19PM -0500, Eric Sandeen wrote:
>> Yeah, I knew it wasn't ;)  I did resend 
>> [PATCH] ext4: fix unjournaled inode bitmap modification
>> which is a bit more involved.
> 
> Yeah, sorry, I didn't see your updated patch at first, since this mail
> thread is one complicated tangle.  :-(
> 
>> That'll get_write_access on the same buffer over and over, I suppose
>> it's ok, but the patch I sent tries to minimize that, and call
>> ext4_handle_release_buffer if we're not going to use it (which is
>> a no-op today anyway and not normally used I guess...)
> 
> Well, it's really rare that we will go through that loop more than
> once; it only happens if we have multiple processes race against each
> other trying to grab the same inode.
> 
>> If ext4_handle_release_buffer() is dead code now, and repeated calls
>> via repeat_in_this_group: are no big deal, then your version looks fine.
> 
> Yeah, I think it's pretty much dead code.  At least, I can't think of
> a good reason why we would want to actually try to handle
> ext4_handle_release_buffer() to claw back the transaciton credit.  And
> if we do, we'll have to do a sweep through the entire ext4 codebase
> anyway.

Yeah, seems that way.

Then your simpler version is probably the way to go.

Thanks,
-Eric

> 						- Ted
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