b=5733,5638

b=5733,5638
Alex's patches to fix small bugs in extents and mballoc:

1) extents-related fixes:
   1) callback's API used in ext3_ext_walk_space() changes a bit to
      reflect that callback can be given >2^16 extent len (hole)
   2) fsfilt_ext3 has changed to use updated callback API
   3) minor race in ext3_ext_new_extent_cb() fixed

2) mballoc-related fixes:
   1) free space searching has changed to be more smart
   2) three possible races have been fixed
   3) lots of minor fixes
   4) mballoc doesn't regenerate buddies in clean umount case