[PATCH 2/3] xfs: remove bitfield based superblock updates

[Christoph Hellwig]

This breaks generic/230 for me on an x86-64 VM:

--- tests/generic/230.out	2013-11-11 10:38:59.000000000 +0000
+++ /root/xfstests/results//generic/230.out.bad	2014-09-26 09:47:37.000000000 +0000
@@ -23,11 +23,8 @@
 Write 900k...
 Rewrite 1001k...
 Write 1000k...
-pwrite64: Disk quota exceeded
 Write 4096...
-pwrite64: Disk quota exceeded
 Touch 3+4
 Touch 5+6
 touch: cannot touch 'SCRATCH_MNT/file6': Disk quota exceeded
 Touch 5
-touch: cannot touch 'SCRATCH_MNT/file5': Disk quota exceeded