GFS2: Use RCU for glock hash table

This has a number of advantages:

 - Reduces contention on the hash table lock
 - Makes the code smaller and simpler
 - Should speed up glock dumps when under load
 - Removes ref count changing in examine_bucket
 - No longer need hash chain lock in glock_put() in common case

There are some further changes which this enables and which
we may do in the future. One is to look at using SLAB_RCU,
and another is to look at using a per-cpu counter for the
per-sb glock counter, since that is touched twice in the
lifetime of each glock (but only used at umount time).

Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

1 files changed, 18 insertions, 21 deletions

diff --git a/fs/gfs2/glock.h b/fs/gfs2/glock.h
index 691851c..afa8bfe 100644
--- a/fs/gfs2/glock.h
+++ b/fs/gfs2/glock.h
@@ -118,7 +118,7 @@ struct lm_lockops {
 	int (*lm_mount) (struct gfs2_sbd *sdp, const char *fsname);
  	void (*lm_unmount) (struct gfs2_sbd *sdp);
 	void (*lm_withdraw) (struct gfs2_sbd *sdp);
-	void (*lm_put_lock) (struct kmem_cache *cachep, struct gfs2_glock *gl);
+	void (*lm_put_lock) (struct gfs2_glock *gl);
 	int (*lm_lock) (struct gfs2_glock *gl, unsigned int req_state,
 			unsigned int flags);
 	void (*lm_cancel) (struct gfs2_glock *gl);
@@ -174,7 +174,7 @@ int gfs2_glock_get(struct gfs2_sbd *sdp,
 		   int create, struct gfs2_glock **glp);
 void gfs2_glock_hold(struct gfs2_glock *gl);
 void gfs2_glock_put_nolock(struct gfs2_glock *gl);
-int gfs2_glock_put(struct gfs2_glock *gl);
+void gfs2_glock_put(struct gfs2_glock *gl);
 void gfs2_holder_init(struct gfs2_glock *gl, unsigned int state, unsigned flags,
 		      struct gfs2_holder *gh);
 void gfs2_holder_reinit(unsigned int state, unsigned flags,
@@ -223,25 +223,22 @@ static inline int gfs2_glock_nq_init(struct gfs2_glock *gl,
 	return error;
 }
 
-/*  Lock Value Block functions  */
-
-int gfs2_lvb_hold(struct gfs2_glock *gl);
-void gfs2_lvb_unhold(struct gfs2_glock *gl);
-
-void gfs2_glock_cb(struct gfs2_glock *gl, unsigned int state);
-void gfs2_glock_complete(struct gfs2_glock *gl, int ret);
-void gfs2_reclaim_glock(struct gfs2_sbd *sdp);
-void gfs2_gl_hash_clear(struct gfs2_sbd *sdp);
-void gfs2_glock_finish_truncate(struct gfs2_inode *ip);
-void gfs2_glock_thaw(struct gfs2_sbd *sdp);
-
-int __init gfs2_glock_init(void);
-void gfs2_glock_exit(void);
-
-int gfs2_create_debugfs_file(struct gfs2_sbd *sdp);
-void gfs2_delete_debugfs_file(struct gfs2_sbd *sdp);
-int gfs2_register_debugfs(void);
-void gfs2_unregister_debugfs(void);
+extern void gfs2_glock_cb(struct gfs2_glock *gl, unsigned int state);
+extern void gfs2_glock_complete(struct gfs2_glock *gl, int ret);
+extern void gfs2_reclaim_glock(struct gfs2_sbd *sdp);
+extern void gfs2_gl_hash_clear(struct gfs2_sbd *sdp);
+extern void gfs2_glock_finish_truncate(struct gfs2_inode *ip);
+extern void gfs2_glock_thaw(struct gfs2_sbd *sdp);
+extern void gfs2_glock_schedule_for_reclaim(struct gfs2_glock *gl);
+extern void gfs2_glock_free(struct rcu_head *rcu);
+
+extern int __init gfs2_glock_init(void);
+extern void gfs2_glock_exit(void);
+
+extern int gfs2_create_debugfs_file(struct gfs2_sbd *sdp);
+extern void gfs2_delete_debugfs_file(struct gfs2_sbd *sdp);
+extern int gfs2_register_debugfs(void);
+extern void gfs2_unregister_debugfs(void);
 
 extern const struct lm_lockops gfs2_dlm_ops;