From: Ashish Sangwan <ashishsangwan2@gmail.com>
Subject: Re: [PATCH] ext4: fix extent tree corruption that incurred by hole punch
Date: Mon, 10 Dec 2012 11:52:39 +0530
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Cc: "Theodore Ts'o" <tytso@mit.edu>,
	ext4 development <linux-ext4@vger.kernel.org>,
	Eric Sandeen <sandeen@redhat.com>
To: Forrest Liu <forrestl@synology.com>
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> Hi Ashish,
>
> First, create a file lager than 4GB, and then punch out every even blocks;
> Use ex command in debugfs to dump extents, belowing is the result.
>
> Level Entries           Logical              Physical Length Flags
>  0/ 3   1/  1       1 - 1048575     40013             1048575
>  1/ 3   1/  5       1 -  231160     40012             231160
>  2/ 3   1/340       1 -     680     40011                680
>  3/ 3   1/340       1 -       1   2228225 -   2228225      1
>  3/ 3   2/340       3 -       3   2228227 -   2228227      1
>  3/ 3   3/340       5 -       5   2228229 -   2228229      1
>
>
> punch out 231159, 231157, ..., 1..
>
>
> Level Entries           Logical              Physical Length Flags
>  0/ 3   1/  1       1 - 1048575     40013             1048575
>  1/ 3   1/  4  231161 -  462320   2457604             231160
>  2/ 3   1/340  231161 -  231840   2457606                680
>  3/ 3   1/340  231161 -  231161   2459385 -   2459385      1
>
>
> Then, we get incorrect logical index, if only do correction in ext4_ext_rm_leaf.

Ok, In your patch we can do without varibale border and instead use:
path->p_idx->ei_block = (path+1)->p_idx->ei_block;

Rest of the patch seems Ok.

Thanks,
Ashish
>
>
> Thanks,
> Forrest