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 <bergwolf@gmail.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
n++;
}
- fiemap->fm_start += fm_ext[i-1].fe_logical +
- fm_ext[i-1].fe_length;
+ fiemap->fm_start = (fm_ext[i-1].fe_logical +
+ fm_ext[i-1].fe_length);
} while (last == 0);
*num_extents = tot_extents;