[XFS] write barrier support  Issue all log sync operations as ordered
writes.  In addition flush the disk cache on fsync if the sync cached
operation didn't sync the log to disk (this requires some additional
bookeping in the transaction and log code). If the device doesn't claim to
support barriers, the filesystem has an extern log volume or the trial
superblock write with barriers enabled failed we disable barriers and
print a warning.  We should probably fail the mount completely, but that
could lead to nasty boot failures for the root filesystem.  Not enabled by
default yet, needs more destructive testing first.

SGI-PV: 912426
SGI-Modid: xfs-linux:xfs-kern:198723a

Signed-off-by: Christoph Hellwig <hch@sgi.com>
Signed-off-by: Nathan Scott <nathans@sgi.com>
diff --git a/fs/xfs/xfs_clnt.h b/fs/xfs/xfs_clnt.h
index b3215ff..c93cb28 100644
--- a/fs/xfs/xfs_clnt.h
+++ b/fs/xfs/xfs_clnt.h
@@ -99,7 +99,7 @@
 						 * enforcement */
 #define XFSMNT_NOUUID		0x01000000	/* Ignore fs uuid */
 #define XFSMNT_DMAPI		0x02000000	/* enable dmapi/xdsm */
-#define XFSMNT_NOLOGFLUSH	0x04000000	/* Don't flush for log blocks */
+#define XFSMNT_BARRIER		0x04000000	/* use write barriers */
 #define XFSMNT_IDELETE		0x08000000	/* inode cluster delete */
 #define XFSMNT_SWALLOC		0x10000000	/* turn on stripe width
 						 * allocation */