[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>

1 files changed, 5 insertions, 0 deletions

diff --git a/fs/xfs/linux-2.6/xfs_buf.c b/fs/xfs/linux-2.6/xfs_buf.c
index 188cbbd5b74a..4663f7dbff1c 100644
--- a/fs/xfs/linux-2.6/xfs_buf.c
+++ b/fs/xfs/linux-2.6/xfs_buf.c
@@ -1295,6 +1295,11 @@ _pagebuf_ioapply(
                 rw = (pb->pb_flags & PBF_READ) ? READ : WRITE;
         }
 
+        if (pb->pb_flags & PBF_ORDERED) {
+                ASSERT(!(pb->pb_flags & PBF_READ));
+                rw = WRITE_BARRIER;
+        }
+
         /* Special code path for reading a sub page size pagebuf in --
          * we populate up the whole page, and hence the other metadata
          * in the same page.  This optimization is only valid when the