filefrag: fix report of number of extents

filefrag has several bugs:

1.
$ touch f1
$ filefrag f1
f1: 1 extent found  ----> bug!
$ filefrag -v f1
Filesystem type is: ef53
File size of f1 is 0 (0 blocks, blocksize 4096)
f1: 0 extents found

2.
$ truncate -s 1m f2
$ filefrag f2
f2: 1 extent found  ----> bug!
$ filefrag -v f2
Filesystem type is: ef53
File size of f2 is 1048576 (256 blocks, blocksize 4096)
f2: 0 extents found

3.
$ for i in `seq 11 -2 0`; do dd if=/dev/zero of=f4 bs=4k count=1 seek=$i conv=notrunc oflag=sync &>/dev/null; done
$ ll f4
-rw-r--r-- 1 root root 49152 Jun  9 15:09 f4
$ filefrag f4
f4: 7 extents found
$ filefrag -v f4
Filesystem type is: ef53
File size of f4 is 49152 (12 blocks, blocksize 4096)
 ext logical physical expected length flags
   0       1  1109993               1
   1       3  1109992  1109994      1
   2       5  1109991  1109993      1
   3       7  1109990  1109992      1
   4       9  1109989  1109991      1
   5      11  1108207  1109990      1 eof
f4: 7 extents found  -----------------------> but we only have 6 extents, bug!

All of these bugs come from the fact that we've made a mistake on
calculating total extents:

o   we set 1 as default for 'total extents', and this will report 1
    extent found even when we don't get any extent from fiemap.
o   if our first extent does not start from 0(logical addr), total
    extents will be one more than what it should be.

Addresses-Red-Hat-Bugzilla: #840848

Reviewed-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: Liu Bo <liubo2009@cn.fujitsu.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

diff --git a/misc/filefrag.c b/misc/filefrag.c
index 0583e91..af008fb 100644 (file)
--- a/misc/filefrag.c
+++ b/misc/filefrag.c
@@ -175,7 +175,7 @@ static int filefrag_fiemap(int fd, int blk_shift, int *num_extents)
        unsigned int i;
        static int fiemap_incompat_printed;
        int fiemap_header_printed = 0;
-       int tot_extents = 1, n = 0;
+       int tot_extents = 0, n = 0;
        int last = 0;
        int rc;
 
@@ -201,25 +201,17 @@ static int filefrag_fiemap(int fd, int blk_shift, int *num_extents)
                        return rc;
                }
 
+               /* If 0 extents are returned, then more ioctls are not needed */
+               if (fiemap->fm_mapped_extents == 0)
+                       break;
+
                if (verbose && !fiemap_header_printed) {
-                       /*
-                        * No extents on first call?
-                        * Skip header and show 0 extents.
-                        */
-                       if (fiemap->fm_mapped_extents == 0) {
-                               *num_extents = 0;
-                               goto out;
-                       }
                        printf(" ext %*s %*s %*s length flags\n", logical_width,
                               "logical", physical_width, "physical",
                               physical_width, "expected");
                        fiemap_header_printed = 1;
                }
 
-               /* If 0 extents are returned, then more ioctls are not needed */
-               if (fiemap->fm_mapped_extents == 0)
-                       break;
-
                for (i = 0; i < fiemap->fm_mapped_extents; i++) {
                        __u64 phy_blk, logical_blk;
                        unsigned long ext_len;
@@ -228,10 +220,13 @@ static int filefrag_fiemap(int fd, int blk_shift, int *num_extents)
                        ext_len = fm_ext[i].fe_length >> blk_shift;
                        logical_blk = fm_ext[i].fe_logical >> blk_shift;
 
-                       if (logical_blk && phy_blk != expected)
+                       if (logical_blk && phy_blk != expected) {
                                tot_extents++;
-                       else
+                       } else {
                                expected = 0;
+                               if (!tot_extents)
+                                       tot_extents = 1;
+                       }
                        if (verbose)
                                print_extent_info(&fm_ext[i], n, expected,
                                                  blk_shift);