On Jun 03, 2009 09:21 +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. > > BTW, should I resend the patch to include the above explanation? Yes, please do. I verified that the code as modified (just '=') is also present in the Lustre fiemap patch, so I'm not sure how it got += there. Possibly from an older version of the patch. > > On Jun 03, 2009 02:03 +0800, Peng Tao wrote: > >> Signed-off-by: Peng Tao <bergwolf@xxxxxxxxx> > >> --- > >> 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 Cheers, Andreas -- Andreas Dilger Sr. Staff Engineer, Lustre Group Sun Microsystems of Canada, Inc. -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
