linux-ext4 - Re: [PATCH] libext2fs: write only core inode in update

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Date:	Wed, 17 Jun 2009 16:36:30 -0500
From:	Eric Sandeen <sandeen@...hat.com>
To:	number9652 <number9652@...oo.com>
CC:	Theodore Tso <tytso@....edu>,
	ext4 development <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH] libext2fs: write only core inode in update_path()

number9652 wrote:
>> number9652 wrote:
>>> --- On Wed, 6/17/09, Eric Sandeen wrote: right way to fix it,
>>> however.  I am concerned
>> that I may have
>>> basically broken write_inode_full on any inode with
>> extents.  For
>>> example, there is another call to write_inode_full in
>> extent.c that
>>> might exhibit this same problem.  I think the
>> right fix would be to
>>> return to reading the full inode into memory in the
>> extent_open
>> 
>> If this is the case (that it's broken now), then we really need 
>> something in the regression suite to catch it - all tests pass in
>> 1.41.6 ....
>> 
>> -Eric
>> 
> I was too general in my statement above about what it broke.  I think
> (didn't test) if a program follows this path: 
> extent_open(...,*handle) write_inode_full(...,handle->inode,...) that
> it will read uninitialized memory in write_inode_full.  It seems
> clear that all previously written code assumes that this path is
> valid, and fixing all that to not assume that would seemingly be much
> more than just what your patch fixes and require more time to test.
> If you only use read/write_inode_full, everything is still okay.
> 
> I think that in this case, even when only using the handle to read
> the inode, we want to have the full inode available (by
> handle->inode) so it is possible (for example) to check the file
> creation time with the returned handle structure.

Seems reasonable to me ...

FWIW, I have Yet Another Case where resize is corrupting the larger
inode, even with this fix and/or my fix.

Still digging into it, sigh.

-Eric
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