[rtems commit] Make bit addressing consistent in rtems_rfs_group.c

[Chris Johns]

Module:    rtems
Branch:    master
Commit:    0c2241c0a923e4ec704fca9bad6bf0a2516ab6bb
Changeset: http://git.rtems.org/rtems/commit/?id=0c2241c0a923e4ec704fca9bad6bf0a2516ab6bb

Author:    Fan Deng <enetor at gmail.com>
Date:      Tue Oct 10 16:11:49 2017 -0700

Make bit addressing consistent in rtems_rfs_group.c

This change fixes https://devel.rtems.org/ticket/3089.

Briefly, rtems_rfs_group.c contains conflicting conversions between
block numbers and group number and bit offset pairs. This caused the
actual bit stored on the bitmask to be one bit displaced from its
intended location.

For more details, please see the associated ticket.

Tested by inspecting the written bitmasks with and without this change.

---

 cpukit/libfs/src/rfs/rtems-rfs-group.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/cpukit/libfs/src/rfs/rtems-rfs-group.c b/cpukit/libfs/src/rfs/rtems-rfs-group.c
index c319dc5..976bac2 100644
--- a/cpukit/libfs/src/rfs/rtems-rfs-group.c
+++ b/cpukit/libfs/src/rfs/rtems-rfs-group.c
@@ -167,7 +167,17 @@ rtems_rfs_group_bitmap_alloc (rtems_rfs_file_system* fs,
     goal -= RTEMS_RFS_ROOT_INO;
   }
   else
+  {
     size = fs->group_blocks;
+    /*
+     * It is possible for 'goal' to be zero. Any newly created inode will have
+     * its 'last_data_block' set to zero, which is then used as 'goal' to
+     * allocate new blocks. When that happens, we simply set 'goal' to zero and
+     * continue the search from there.
+     */
+    if (goal >= RTEMS_RFS_ROOT_INO)
+        goal -= RTEMS_RFS_ROOT_INO;
+  }
 
   group_start = goal / size;
   bit = (rtems_rfs_bitmap_bit) (goal % size);
@@ -324,8 +334,9 @@ rtems_rfs_group_bitmap_test (rtems_rfs_file_system* fs,
   }
   else
   {
-    if (no >= rtems_rfs_fs_blocks (fs))
+    if ((no < RTEMS_RFS_ROOT_INO) || (no >= rtems_rfs_fs_blocks (fs)))
         return EINVAL;
+    no -= RTEMS_RFS_ROOT_INO;
     size = fs->group_blocks;
   }