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>
diff --git a/fs/gfs2/incore.h b/fs/gfs2/incore.h
index a79790c..720c1e6 100644
--- a/fs/gfs2/incore.h
+++ b/fs/gfs2/incore.h
@@ -15,6 +15,8 @@
#include <linux/workqueue.h>
#include <linux/dlm.h>
#include <linux/buffer_head.h>
+#include <linux/rcupdate.h>
+#include <linux/rculist_bl.h>
#define DIO_WAIT 0x00000010
#define DIO_METADATA 0x00000020
@@ -201,7 +203,7 @@
};
struct gfs2_glock {
- struct hlist_node gl_list;
+ struct hlist_bl_node gl_list;
unsigned long gl_flags; /* GLF_... */
struct lm_lockname gl_name;
atomic_t gl_ref;
@@ -234,6 +236,7 @@
atomic_t gl_ail_count;
struct delayed_work gl_work;
struct work_struct gl_delete;
+ struct rcu_head gl_rcu;
};
#define GFS2_MIN_LVB_SIZE 32 /* Min size of LVB that gfs2 supports */