On Mon, Oct 06, 2014 at 07:05:39PM +0800, Xiaoguang Wang wrote:
> When using FIBMAP and '-e' option is specified, the calculation for fiemap_extent
> is wrong, we wrongly updated fm_ext.fe_logical for every iteration, please see the
> code in the end of 'for' loop in fm_ext.fe_logical().
>
> In an ext2 file system(block size is 1024 bytes),
> dd if=/dev/zero of=testfile bs=1k count=15
> Using debugfs, corresponding physical blocks are "2049 2050 2051 2052 2053 2054
> 2055 2056 2057 2058 2059 2060 1025 2061 2062 2063", 1025 is this indirect block.
> Before this patch, filefrag's output would be:
> filefrag -B -e testfile
> Filesystem type is: ef53
> Filesystem cylinder groups approximately 16
> File size of testfile is 15360 (15 blocks of 1024 bytes)
> ext: logical_offset: physical_offset: length: expected: flags:
> 0: 1.. 2: 2050.. 2051: 2: 2051: merged
> 1: 3.. 4: 2052.. 2053: 2: 2053: merged
> 2: 5.. 6: 2054.. 2055: 2: 2055: merged
> 3: 7.. 8: 2056.. 2057: 2: 2057: merged
> 4: 9.. 10: 2058.. 2059: 2: 2059: merged
> 5: 11.. 12: 2060.. 2061: 2: 2062: merged
> 6: 13.. 14: 2062.. 2063: 2: 2063: merged,eof
> 7: 14.. 14: 2063.. 2063: 1: 2063: merged,eof
> This output is not reasonable.
It's just plain whacky. Why would logical offset 14 be listed twice? :)
> Fix this bug and try to make it readable. After this patch, the output would be:
> ./filefrag -B -e mntpoint/testfile
> Filesystem type is: ef53
> Filesystem cylinder groups approximately 16
> File size of mntpoint/testfile is 15360 (15 blocks of 1024 bytes)
> ext: logical_offset: physical_offset: length: expected: flags:
> 0: 0.. 11: 2049.. 2060: 12: 2062: merged
> 1: 12.. 14: 2061.. 2063: 3: 2063: merged,eof
> mntpoint/testfile: 2 extents found, perfection would be 1 extent
Where'd the indirect block end up, if not in the middle of 2049-2063?
> Signed-off-by: Xiaoguang Wang <wangxg.fnst@xxxxxxxxxxxxxx>
> ---
> misc/filefrag.c | 37 +++++++++++++++++++++++--------------
> 1 file changed, 23 insertions(+), 14 deletions(-)
>
> diff --git a/misc/filefrag.c b/misc/filefrag.c
> index c1a8684..e9f7e68 100644
> --- a/misc/filefrag.c
> +++ b/misc/filefrag.c
> @@ -315,32 +315,41 @@ static int filefrag_fibmap(int fd, int blk_shift, int *num_extents,
> return rc;
> if (block == 0)
> continue;
> + count++;
> +
> if (*num_extents == 0) {
> (*num_extents)++;
> if (force_extent) {
> print_extent_header();
> + fm_ext.fe_logical = logical;
> fm_ext.fe_physical = block * st->st_blksize;
> + fm_ext.fe_length = st->st_blksize;
> }
> + last_block = block;
> + continue;
> }
> - count++;
> - if (force_extent && last_block != 0 &&
> - (block != last_block + 1 ||
> - fm_ext.fe_logical + fm_ext.fe_length != logical)) {
> - print_extent_info(&fm_ext, *num_extents - 1,
> - (last_block + 1) * st->st_blksize,
> - blk_shift, st);
> - fm_ext.fe_length = 0;
> - (*num_extents)++;
> +
> + if (force_extent) {
> + if (block != last_block + 1 ||
> + fm_ext.fe_length + fm_ext.fe_logical != logical) {
> + print_extent_info(&fm_ext, *num_extents - 1,
> + (last_block + 1) *
> + st->st_blksize,
> + blk_shift, st);
> + fm_ext.fe_logical = logical;
> + fm_ext.fe_physical = block * st->st_blksize;
> + fm_ext.fe_length = st->st_blksize;
> + (*num_extents)++;
> + } else {
> + fm_ext.fe_length += st->st_blksize;
> + }
> } else if (last_block && (block != last_block + 1)) {
> - if (verbose)
> + if (verbose) {
> printf("Discontinuity: Block %ld is at %lu (was "
> "%lu)\n", i, block, last_block + 1);
> - fm_ext.fe_length = 0;
> + }
The { } is not needed for a single line if statement.
> (*num_extents)++;
> }
> - fm_ext.fe_logical = logical;
> - fm_ext.fe_physical = block * st->st_blksize;
> - fm_ext.fe_length += st->st_blksize;
> last_block = block;
Otherwise, I think this looks decent.
--D
> }
>
> --
> 1.8.2.1
>
> --
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