xfs: use proper interfaces for on-stack plugging

Add proper blk_start_plug/blk_finish_plug pairs for the two places where
we issue buffer I/O, and remove the blk_flush_plug in xfs_buf_lock and
xfs_buf_iowait, given that context switches already flush the per-process
plugging lists.

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

1 files changed, 9 insertions, 11 deletions

diff --git a/fs/xfs/linux-2.6/xfs_buf.c b/fs/xfs/linux-2.6/xfs_buf.c
index 2eef165f4f39..478ca1547ee5 100644
--- a/fs/xfs/linux-2.6/xfs_buf.c
+++ b/fs/xfs/linux-2.6/xfs_buf.c
@@ -915,8 +915,6 @@ xfs_buf_lock(
 
         if (atomic_read(&bp->b_pin_count) && (bp->b_flags & XBF_STALE))
                 xfs_log_force(bp->b_target->bt_mount, 0);
-        if (atomic_read(&bp->b_io_remaining))
-                blk_flush_plug(current);
         down(&bp->b_sema);
         XB_SET_OWNER(bp);
 
@@ -1305,8 +1303,6 @@ xfs_buf_iowait(
 {
         trace_xfs_buf_iowait(bp, _RET_IP_);
 
-        if (atomic_read(&bp->b_io_remaining))
-                blk_flush_plug(current);
         wait_for_completion(&bp->b_iowait);
 
         trace_xfs_buf_iowait_done(bp, _RET_IP_);
@@ -1743,8 +1739,8 @@ xfsbufd(
         do {
                 long    age = xfs_buf_age_centisecs * msecs_to_jiffies(10);
                 long    tout = xfs_buf_timer_centisecs * msecs_to_jiffies(10);
-                int     count = 0;
                 struct list_head tmp;
+                struct blk_plug plug;
 
                 if (unlikely(freezing(current))) {
                         set_bit(XBT_FORCE_SLEEP, &target->bt_flags);
@@ -1760,16 +1756,15 @@ xfsbufd(
 
                 xfs_buf_delwri_split(target, &tmp, age);
                 list_sort(NULL, &tmp, xfs_buf_cmp);
+
+                blk_start_plug(&plug);
                 while (!list_empty(&tmp)) {
                         struct xfs_buf *bp;
                         bp = list_first_entry(&tmp, struct xfs_buf, b_list);
                         list_del_init(&bp->b_list);
                         xfs_bdstrat_cb(bp);
-                        count++;
                 }
-                if (count)
-                        blk_flush_plug(current);
-
+                blk_finish_plug(&plug);
         } while (!kthread_should_stop());
 
         return 0;
@@ -1789,6 +1784,7 @@ xfs_flush_buftarg(
         int             pincount = 0;
         LIST_HEAD(tmp_list);
         LIST_HEAD(wait_list);
+        struct blk_plug plug;
 
         xfs_buf_runall_queues(xfsconvertd_workqueue);
         xfs_buf_runall_queues(xfsdatad_workqueue);
@@ -1803,6 +1799,8 @@ xfs_flush_buftarg(
          * we do that after issuing all the IO.
          */
         list_sort(NULL, &tmp_list, xfs_buf_cmp);
+
+        blk_start_plug(&plug);
         while (!list_empty(&tmp_list)) {
                 bp = list_first_entry(&tmp_list, struct xfs_buf, b_list);
                 ASSERT(target == bp->b_target);
@@ -1813,10 +1811,10 @@ xfs_flush_buftarg(
                 }
                 xfs_bdstrat_cb(bp);
         }
+        blk_finish_plug(&plug);
 
         if (wait) {
-                /* Expedite and wait for IO to complete. */
-                blk_flush_plug(current);
+                /* Wait for IO to complete. */
                 while (!list_empty(&wait_list)) {
                         bp = list_first_entry(&wait_list, struct xfs_buf, b_list);