xfs: improve metadata I/O merging in the elevator

Change all async metadata buffers to use [READ|WRITE]_META I/O types
so that the I/O doesn't get issued immediately. This allows merging of
adjacent metadata requests but still prioritises them over bulk data.
This shows a 10-15% improvement in sequential create speed of small
files.

Don't include the log buffers in this classification - leave them as
sync types so they are issued immediately.

Signed-off-by: Dave Chinner <dgc@sgi.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Alex Elder <aelder@sgi.com>

1 files changed, 5 insertions, 1 deletions

diff --git a/fs/xfs/linux-2.6/xfs_buf.c b/fs/xfs/linux-2.6/xfs_buf.c
index b4c7d4248aac..162359b664ca 100644
--- a/fs/xfs/linux-2.6/xfs_buf.c
+++ b/fs/xfs/linux-2.6/xfs_buf.c
@@ -1149,10 +1149,14 @@ _xfs_buf_ioapply(
         if (bp->b_flags & XBF_ORDERED) {
                 ASSERT(!(bp->b_flags & XBF_READ));
                 rw = WRITE_BARRIER;
-        } else if (bp->b_flags & _XBF_RUN_QUEUES) {
+        } else if (bp->b_flags & XBF_LOG_BUFFER) {
                 ASSERT(!(bp->b_flags & XBF_READ_AHEAD));
                 bp->b_flags &= ~_XBF_RUN_QUEUES;
                 rw = (bp->b_flags & XBF_WRITE) ? WRITE_SYNC : READ_SYNC;
+        } else if (bp->b_flags & _XBF_RUN_QUEUES) {
+                ASSERT(!(bp->b_flags & XBF_READ_AHEAD));
+                bp->b_flags &= ~_XBF_RUN_QUEUES;
+                rw = (bp->b_flags & XBF_WRITE) ? WRITE_META : READ_META;
         } else {
                 rw = (bp->b_flags & XBF_WRITE) ? WRITE :
                      (bp->b_flags & XBF_READ_AHEAD) ? READA : READ;