GFS2: Alter point of entry to glock lru list for glocks with an address_space

Rather than allowing the glocks to be scheduled for possible
reclaim as soon as they have exited the journal, this patch
delays their entry to the list until the glocks in question
are no longer in use.

This means that we will rely on the vm for writeback of all
dirty data and metadata from now on. When glocks are added
to the lru list they should be freeable much faster since all
the I/O required to free them should have already been completed.

This should lead to much better I/O patterns under low memory
conditions.

Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>

1 files changed, 15 insertions, 18 deletions

diff --git a/fs/gfs2/glock.c b/fs/gfs2/glock.c
index f07643e21bfa..1019183232fe 100644
--- a/fs/gfs2/glock.c
+++ b/fs/gfs2/glock.c
@@ -160,6 +160,19 @@ static int demote_ok(const struct gfs2_glock *gl)
 }
 
 
+void gfs2_glock_add_to_lru(struct gfs2_glock *gl)
+{
+        spin_lock(&lru_lock);
+
+        if (!list_empty(&gl->gl_lru))
+                list_del_init(&gl->gl_lru);
+        else
+                atomic_inc(&lru_count);
+
+        list_add_tail(&gl->gl_lru, &lru_list);
+        spin_unlock(&lru_lock);
+}
+
 /**
  * __gfs2_glock_schedule_for_reclaim - Add a glock to the reclaim list
  * @gl: the glock
@@ -170,24 +183,8 @@ static int demote_ok(const struct gfs2_glock *gl)
 
 static void __gfs2_glock_schedule_for_reclaim(struct gfs2_glock *gl)
 {
-        if (demote_ok(gl)) {
-                spin_lock(&lru_lock);
-
-                if (!list_empty(&gl->gl_lru))
-                        list_del_init(&gl->gl_lru);
-                else
-                        atomic_inc(&lru_count);
-
-                list_add_tail(&gl->gl_lru, &lru_list);
-                spin_unlock(&lru_lock);
-        }
-}
-
-void gfs2_glock_schedule_for_reclaim(struct gfs2_glock *gl)
-{
-        spin_lock(&gl->gl_spin);
-        __gfs2_glock_schedule_for_reclaim(gl);
-        spin_unlock(&gl->gl_spin);
+        if (demote_ok(gl))
+                gfs2_glock_add_to_lru(gl);
 }
 
 /**