[GFS2] Use hlist for glock hash chains

This results in smaller list heads, so that we can have more chains
in the same amount of memory (twice as many). I've multiplied the
size of the table by four though - this is because we are saving
memory by not having one lock per chain any more. So we land up
using about the same amount of memory for the hash table as we
did before I started these changes, the difference being that we
now have four times as many hash chains.

The reason that I say "about the same amount of memory" is that the
actual amount now depends upon the NR_CPUS and some of the config
variables, so that its not exact and in some cases we do use more
memory. Eventually we might want to scale the hash table size
according to the size of physical ram as measured on module load.

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

3 files changed, 18 insertions, 14 deletions

diff --git a/fs/gfs2/glock.c b/fs/gfs2/glock.c
index b5effb9e4a3..cf54b0b001f 100644
--- a/fs/gfs2/glock.c
+++ b/fs/gfs2/glock.c
@@ -40,7 +40,7 @@ struct greedy {
 };
 
 struct gfs2_gl_hash_bucket {
-        struct list_head hb_list;
+        struct hlist_head hb_list;
 };
 
 typedef void (*glock_examiner) (struct gfs2_glock * gl);
@@ -49,7 +49,7 @@ static int gfs2_dump_lockstate(struct gfs2_sbd *sdp);
 static int dump_glock(struct gfs2_glock *gl);
 static int dump_inode(struct gfs2_inode *ip);
 
-#define GFS2_GL_HASH_SHIFT      13
+#define GFS2_GL_HASH_SHIFT      15
 #define GFS2_GL_HASH_SIZE       (1 << GFS2_GL_HASH_SHIFT)
 #define GFS2_GL_HASH_MASK       (GFS2_GL_HASH_SIZE - 1)
 
@@ -210,7 +210,7 @@ int gfs2_glock_put(struct gfs2_glock *gl)
 
 	write_lock(gl_lock_addr(gl->gl_hash));
 	if (kref_put(&gl->gl_ref, kill_glock)) {
-		list_del_init(&gl->gl_list);
+		hlist_del(&gl->gl_list);
 		write_unlock(gl_lock_addr(gl->gl_hash));
 		BUG_ON(spin_is_locked(&gl->gl_spin));
 		glock_free(gl);
@@ -259,8 +259,9 @@ static struct gfs2_glock *search_bucket(unsigned int hash,
 					const struct lm_lockname *name)
 {
 	struct gfs2_glock *gl;
+	struct hlist_node *h;
 
-	list_for_each_entry(gl, &gl_hash_table[hash].hb_list, gl_list) {
+	hlist_for_each_entry(gl, h, &gl_hash_table[hash].hb_list, gl_list) {
 		if (!lm_name_equal(&gl->gl_name, name))
 			continue;
 		if (gl->gl_sbd != sdp)
@@ -368,7 +369,7 @@ int gfs2_glock_get(struct gfs2_sbd *sdp, u64 number,
 		glock_free(gl);
 		gl = tmp;
 	} else {
-		list_add_tail(&gl->gl_list, &gl_hash_table[hash].hb_list);
+		hlist_add_head(&gl->gl_list, &gl_hash_table[hash].hb_list);
 		write_unlock(gl_lock_addr(hash));
 	}
 
@@ -1895,15 +1896,15 @@ static int examine_bucket(glock_examiner examiner, struct gfs2_sbd *sdp,
 {
 	struct gfs2_glock *gl, *prev = NULL;
 	int has_entries = 0;
-	struct list_head *head = &gl_hash_table[hash].hb_list;
+	struct hlist_head *head = &gl_hash_table[hash].hb_list;
 
 	read_lock(gl_lock_addr(hash));
-	/* Can't use list_for_each_entry - don't want prefetch here */
-	if (list_empty(head))
+	/* Can't use hlist_for_each_entry - don't want prefetch here */
+	if (hlist_empty(head))
 		goto out;
 	has_entries = 1;
-	gl = list_entry(head->next, struct gfs2_glock, gl_list);
-	while(&gl->gl_list != head) {
+	gl = list_entry(head->first, struct gfs2_glock, gl_list);
+	while(1) {
 		if (gl->gl_sbd == sdp) {
 			gfs2_glock_hold(gl);
 			read_unlock(gl_lock_addr(hash));
@@ -1913,6 +1914,8 @@ static int examine_bucket(glock_examiner examiner, struct gfs2_sbd *sdp,
 			examiner(gl);
 			read_lock(gl_lock_addr(hash));
 		}
+		if (gl->gl_list.next == NULL)
+			break;
 		gl = list_entry(gl->gl_list.next, struct gfs2_glock, gl_list);
 	}
 out:
@@ -2195,6 +2198,7 @@ out:
 static int gfs2_dump_lockstate(struct gfs2_sbd *sdp)
 {
 	struct gfs2_glock *gl;
+	struct hlist_node *h;
 	unsigned int x;
 	int error = 0;
 
@@ -2202,7 +2206,7 @@ static int gfs2_dump_lockstate(struct gfs2_sbd *sdp)
 
 		read_lock(gl_lock_addr(x));
 
-		list_for_each_entry(gl, &gl_hash_table[x].hb_list, gl_list) {
+		hlist_for_each_entry(gl, h, &gl_hash_table[x].hb_list, gl_list) {
 			if (gl->gl_sbd != sdp)
 				continue;
 
@@ -2225,7 +2229,7 @@ int __init gfs2_glock_init(void)
 {
 	unsigned i;
 	for(i = 0; i < GFS2_GL_HASH_SIZE; i++) {
-		INIT_LIST_HEAD(&gl_hash_table[i].hb_list);
+		INIT_HLIST_HEAD(&gl_hash_table[i].hb_list);
 	}
 #ifdef GL_HASH_LOCK_SZ
 	for(i = 0; i < GL_HASH_LOCK_SZ; i++) {
diff --git a/fs/gfs2/incore.h b/fs/gfs2/incore.h
index 1fed8d1abae..c68d39271ed 100644
--- a/fs/gfs2/incore.h
+++ b/fs/gfs2/incore.h
@@ -161,7 +161,7 @@ enum {
 };
 
 struct gfs2_glock {
-	struct list_head gl_list;
+	struct hlist_node gl_list;
 	unsigned long gl_flags;		/* GLF_... */
 	struct lm_lockname gl_name;
 	struct kref gl_ref;
diff --git a/fs/gfs2/main.c b/fs/gfs2/main.c
index 2bdf246436c..d2867988cc3 100644
--- a/fs/gfs2/main.c
+++ b/fs/gfs2/main.c
@@ -42,7 +42,7 @@ static void gfs2_init_glock_once(void *foo, kmem_cache_t *cachep, unsigned long
 	struct gfs2_glock *gl = foo;
 	if ((flags & (SLAB_CTOR_VERIFY|SLAB_CTOR_CONSTRUCTOR)) ==
 	    SLAB_CTOR_CONSTRUCTOR) {
-		INIT_LIST_HEAD(&gl->gl_list);
+		INIT_HLIST_NODE(&gl->gl_list);
 		spin_lock_init(&gl->gl_spin);
 		INIT_LIST_HEAD(&gl->gl_holders);
 		INIT_LIST_HEAD(&gl->gl_waiters1);