fiemap: Fix semantics of max_extents (-n arguments)

Currently the semantics of the -n argument are a bit idiosyncratic. We want the
argument to be the limit of extents that are going to be output by the tool. This
is clearly broken now as evident from the following example on a fragmented file:

xfs_io -c "fiemap -v -n 5" test-dir/fragmented-file
test-dir/fragmented-file:
 EXT: FILE-OFFSET      BLOCK-RANGE          TOTAL FLAGS
   0: [0..15]:         hole                    16
   1: [16..23]:        897847296..897847303     8   0x0
   2: [24..31]:        hole                     8
   3: [32..39]:        897851392..897851399     8   0x0

So we want at most 5 extents printed, yet we get 4. So we always print n - 1
extents.

With this modification the output looks like:

xfs_io -c "fiemap -v -n 5" test-dir/fragmented-file
test-dir/fragmented-file:
 EXT: FILE-OFFSET      BLOCK-RANGE          TOTAL FLAGS
   0: [0..15]:         hole                    16
   1: [16..23]:        897847296..897847303     8   0x0
   2: [24..31]:        hole                     8
   3: [32..39]:        897851392..897851399     8   0x0
   4: [40..47]:        hole                     8

Signed-off-by: Nikolay Borisov <nborisov@suse.com>
[sandeen: fix initialization of max_extents]
Reviewed-by: Eric Sandeen <sandeen@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Eric Sandeen <sandeen@sandeen.net>

diff --git a/io/fiemap.c b/io/fiemap.c
index 44a64870d7113b726e5fddd0730235aa403ec4f6..e6fd66da753dd0380dee2860656621b27fe3af0a 100644 (file)
--- a/io/fiemap.c
+++ b/io/fiemap.c
@@ -26,7 +26,7 @@
 #define EXTENT_BATCH 32
 
 static cmdinfo_t fiemap_cmd;
-static int max_extents = 0;
+static int max_extents = -1;
 
 static void
 fiemap_help(void)
@@ -122,7 +122,7 @@ print_verbose(
                cur_extent++;
        }
 
-       if ((cur_extent + 1) == max_extents)
+       if (cur_extent == max_extents)
                return 1;
 
        snprintf(lbuf, sizeof(lbuf), "[%llu..%llu]:", lstart,
@@ -157,7 +157,7 @@ print_plain(
                cur_extent++;
        }
 
-       if ((cur_extent + 1) == max_extents)
+       if (cur_extent == max_extents)
                return 1;
 
        printf("\t%d: [%llu..%llu]: %llu..%llu", cur_extent,
@@ -264,7 +264,7 @@ fiemap_f(
 
        printf("%s:\n", file->name);
 
-       while (!last && ((cur_extent + 1) != max_extents)) {
+       while (!last && (cur_extent != max_extents)) {
 
                memset(fiemap, 0, map_size);
                fiemap->fm_flags = fiemap_flags;
@@ -314,12 +314,12 @@ fiemap_f(
                                break;
                        }
 
-                       if ((cur_extent + 1) == max_extents)
+                       if (cur_extent == max_extents)
                                break;
                }
        }
 
-       if ((cur_extent + 1) == max_extents)
+       if (cur_extent  == max_extents)
                goto out;
 
        memset(&st, 0, sizeof(st));