gfs2: Don't get stuck with I/O plugged in gfs2_ail1_flush

In gfs2_ail1_flush, we're using I/O plugging to give the block layer a
better chance of merging I/O requests.  If we're too aggressive here, we
can end up waiting on I/O to complete while still plugged.  Fix that in
a way similar to writeback_sb_inodes, except that we can't use
blk_flush_plug because blk_flush_plug_list is not exported.

Signed-off-by: Bob Peterson <rpeterso@redhat.com>
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>

diff --git a/fs/gfs2/log.c b/fs/gfs2/log.c
index a6fbde9..16937eb 100644 (file)
--- a/fs/gfs2/log.c
+++ b/fs/gfs2/log.c
@@ -91,7 +91,7 @@ void gfs2_remove_from_ail(struct gfs2_bufdata *bd)
 
 static int gfs2_ail1_start_one(struct gfs2_sbd *sdp,
                               struct writeback_control *wbc,
-                              struct gfs2_trans *tr)
+                              struct gfs2_trans *tr, struct blk_plug *plug)
 __releases(&sdp->sd_ail_lock)
 __acquires(&sdp->sd_ail_lock)
 {
@@ -133,6 +133,11 @@ __acquires(&sdp->sd_ail_lock)
                        continue;
                spin_unlock(&sdp->sd_ail_lock);
                ret = generic_writepages(mapping, wbc);
+               if (need_resched()) {
+                       blk_finish_plug(plug);
+                       cond_resched();
+                       blk_start_plug(plug);
+               }
                spin_lock(&sdp->sd_ail_lock);
                if (ret == -ENODATA) /* if a jdata write into a new hole */
                        ret = 0; /* ignore it */
@@ -207,7 +212,7 @@ restart:
        list_for_each_entry_reverse(tr, head, tr_list) {
                if (wbc->nr_to_write <= 0)
                        break;
-               ret = gfs2_ail1_start_one(sdp, wbc, tr);
+               ret = gfs2_ail1_start_one(sdp, wbc, tr, &plug);
                if (ret) {
                        if (ret == -EBUSY)
                                goto restart;