linux-ext4 - Re: [PATCH] libext2fs: reset handle after inserting new extent

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Date:	Tue, 07 Jul 2009 09:22:18 -0500
From:	Eric Sandeen <sandeen@...hat.com>
To:	Theodore Tso <tytso@....edu>
CC:	ext4 development <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH] libext2fs: reset handle after inserting new extent

Theodore Tso wrote:
> On Mon, Jul 06, 2009 at 05:15:07PM -0500, Eric Sandeen wrote:
>> Commit 53422e8a5644e22ea3f6e0efba82a765b72e4308 moved
>> the new extent insertion in ext2fs_extent_set_bmap prior
>> to the modification of the original extent, but the
>> insert function left the handle pointing a the new
>> extent; this left us modifying the -new- extent not
>> the original one, and winding up with a corrupt extent
>> tree something like:
>>
>> BLOCKS:
>> (0-1):588791-588792, (0):588791
>>
>> We need to move back to the previous extent prior
>> to modification, if we inserted a new one.
> 
> Hmm, I just thought of something awful; what if the insert resulted in
> a node split?  Instead of using ext2fs_extent_get(EXT2_EXTENT_PREV),
> we may need to use ext2fs_extent_goto() to seek to the correct logical
> block instead.
> 
> 						- Ted

Hm....

so PREV doesn't go to the node for the previous logical block, but to
what, the node to the left at this level?  Guess I need to read more
carefully...

-Eric
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