2009-06-04 01:19:11

by Peng Tao

Subject: [PATCH-e2fsprogs-resend] filefrag: fix fm_start in filefrag_fiemap loop

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.

Signed-off-by: Peng Tao <[email protected]>
---
misc/filefrag.c | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/misc/filefrag.c b/misc/filefrag.c
index 6bea2cd..7786646 100644
--- a/misc/filefrag.c
+++ b/misc/filefrag.c
@@ -239,7 +239,7 @@ int filefrag_fiemap(int fd, int blk_shift, int *num_extents)
n++;
}

- fiemap->fm_start += fm_ext[i-1].fe_logical +
+ fiemap->fm_start = fm_ext[i-1].fe_logical +
fm_ext[i-1].fe_length;
} while (last == 0);

--
1.6.2.GIT

2009-07-02 04:25:01

by Theodore Ts'o

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