[rtems commit] For PR 2164 - RFS File System - fix bitmap_create_search loop bug

[Chris Johns]

Module:    rtems
Branch:    master
Commit:    a9619f3cb6b181f781aaf1f77931b32d0137145f
Changeset: http://git.rtems.org/rtems/commit/?id=a9619f3cb6b181f781aaf1f77931b32d0137145f

Author:    Alan Cudmore <alan.cudmore at gmail.com>
Date:      Wed Dec 18 12:00:42 2013 -0500

For PR 2164 - RFS File System - fix bitmap_create_search loop bug

This is for the RFS file system. There is a bug in the
rtems_rfs_bitmap_create_search loop. It is supposed to iterate
over the range of bits in a search element ( usually 32 bits ),
so it should loop through bits 0 through 31. Instead it loops
through 0 - 32, causing some blocks not to be allocated. As in
PR 2163, this depends on the block size and number of blocks in
a file system. Block sizes and group sizes that are powers of 2
seem to work fine ( 512 byte blocks, 4096 block groups, etc ).
When the block sizes are not powers of 2, then this loop error
causes some of the blocks at the end of a group to be skipped,
preventing 100% of the blocks from being used. A simple test
for this and PR2163 is to create a RAM disk with block size
3900 and at least 1 full group ( 31200 blocks ). A file system
with these sizes will not be able to allocate 100% of the blocks.

---

 cpukit/libfs/src/rfs/rtems-rfs-bitmaps.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/cpukit/libfs/src/rfs/rtems-rfs-bitmaps.c b/cpukit/libfs/src/rfs/rtems-rfs-bitmaps.c
index c4050b2..b8bd0b3 100644
--- a/cpukit/libfs/src/rfs/rtems-rfs-bitmaps.c
+++ b/cpukit/libfs/src/rfs/rtems-rfs-bitmaps.c
@@ -599,7 +599,8 @@ rtems_rfs_bitmap_create_search (rtems_rfs_bitmap_control* control)
 
     size -= available;
 
-    if (bit == rtems_rfs_bitmap_element_bits ())
+    /* Iterate from 0 to 1 less than the number of bits in an element */
+    if (bit == (rtems_rfs_bitmap_element_bits () - 1))
     {
       bit = 0;
       search_map++;