linux-ext4 - Re: [PATCH-e2fsprogs-resend] filefrag: fix fm_start in filefrag

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Date:	Thu, 2 Jul 2009 00:24:59 -0400
From:	Theodore Tso <tytso@....edu>
To:	Peng Tao <bergwolf@...il.com>
Cc:	linux-ext4@...r.kernel.org, Andreas Dilger <adilger@....com>
Subject: Re: [PATCH-e2fsprogs-resend] filefrag: fix fm_start in
	filefrag_fiemap loop

On Thu, Jun 04, 2009 at 09:18:40AM +0800, Peng Tao wrote:
> When used with -v and the targeted file has more than 144 extents(double of
> the length of fm_extents array provided by buf), filefrag_fiemap loops and
> calls fiemap ioctl() multiple times to calculate the actual number of extents
> in a file. Each call to fiemap ioctl() uses  fm_start as the starting logical
> offset. The patch fixes fm_start in each loop( except for the first one) and
> makes the extent calculation correct for files with more that 144 extents.  
> 
> To produce the problem, first run filefrag -v on a highly fragmented file.
> Then change the buf size in filefrag_fiemap to make it large enough to have
> all the extent mapped in a single loop and run filefrag -v after recompiling.
> The former will produce a much smaller extent count because of the false
> fm_start used in the loop. And the two will produce different extent output
> since the 145th extent.

Thanks, applied.

						- Ted
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