dlm: use rwlock for rsb hash table

The conversion to rhashtable introduced a hash table lock per lockspace,
in place of per bucket locks.  To make this more scalable, switch to
using a rwlock for hash table access.  The common case fast path uses
it as a read lock.
Signed-off-by: Alexander Aring <aahringo@redhat.com>
Signed-off-by: David Teigland <teigland@redhat.com>

fs/dlm/debug_fs.c

@@ -413,7 +413,7 @@ static void *table_seq_start(struct seq_file *seq, loff_t *pos)
 	else
 		list = &ls->ls_keep;
 
-	spin_lock_bh(&ls->ls_rsbtbl_lock);
+	read_lock_bh(&ls->ls_rsbtbl_lock);
 	return seq_list_start(list, *pos);
 }
 
@@ -434,7 +434,7 @@ static void table_seq_stop(struct seq_file *seq, void *iter_ptr)
 {
 	struct dlm_ls *ls = seq->private;
 
-	spin_unlock_bh(&ls->ls_rsbtbl_lock);
+	read_unlock_bh(&ls->ls_rsbtbl_lock);
 }
 
 static const struct seq_operations format1_seq_ops = {

fs/dlm/dir.c

@@ -200,9 +200,9 @@ static struct dlm_rsb *find_rsb_root(struct dlm_ls *ls, const char *name,
 	struct dlm_rsb *r;
 	int rv;
 
-	spin_lock_bh(&ls->ls_rsbtbl_lock);
+	read_lock_bh(&ls->ls_rsbtbl_lock);
 	rv = dlm_search_rsb_tree(&ls->ls_rsbtbl, name, len, &r);
-	spin_unlock_bh(&ls->ls_rsbtbl_lock);
+	read_unlock_bh(&ls->ls_rsbtbl_lock);
 	if (!rv)
 		return r;
 

fs/dlm/dlm_internal.h

@@ -585,7 +585,7 @@ struct dlm_ls {
 	spinlock_t		ls_lkbidr_spin;
 
 	struct rhashtable	ls_rsbtbl;
-	spinlock_t		ls_rsbtbl_lock;
+	rwlock_t		ls_rsbtbl_lock;
 
 	struct list_head	ls_toss;
 	struct list_head	ls_keep;

fs/dlm/lockspace.c

@@ -424,7 +424,7 @@ static int new_lockspace(const char *name, const char *cluster,
 
 	INIT_LIST_HEAD(&ls->ls_toss);
 	INIT_LIST_HEAD(&ls->ls_keep);
-	spin_lock_init(&ls->ls_rsbtbl_lock);
+	rwlock_init(&ls->ls_rsbtbl_lock);
 
 	error = rhashtable_init(&ls->ls_rsbtbl, &dlm_rhash_rsb_params);
 	if (error)

fs/dlm/recover.c

@@ -884,7 +884,7 @@ void dlm_clear_toss(struct dlm_ls *ls)
 	struct dlm_rsb *r, *safe;
 	unsigned int count = 0;
 
-	spin_lock_bh(&ls->ls_rsbtbl_lock);
+	write_lock_bh(&ls->ls_rsbtbl_lock);
 	list_for_each_entry_safe(r, safe, &ls->ls_toss, res_rsbs_list) {
 		list_del(&r->res_rsbs_list);
 		rhashtable_remove_fast(&ls->ls_rsbtbl, &r->res_node,
@@ -897,7 +897,7 @@ void dlm_clear_toss(struct dlm_ls *ls)
 		free_toss_rsb(r);
 		count++;
 	}
-	spin_unlock_bh(&ls->ls_rsbtbl_lock);
+	write_unlock_bh(&ls->ls_rsbtbl_lock);
 
 	if (count)
 		log_rinfo(ls, "dlm_clear_toss %u done", count);

fs/dlm/recoverd.c

@@ -32,7 +32,7 @@ static int dlm_create_masters_list(struct dlm_ls *ls)
 		goto out;
 	}
 
-	spin_lock_bh(&ls->ls_rsbtbl_lock);
+	read_lock_bh(&ls->ls_rsbtbl_lock);
 	list_for_each_entry(r, &ls->ls_keep, res_rsbs_list) {
 		if (r->res_nodeid)
 			continue;
@@ -40,7 +40,7 @@ static int dlm_create_masters_list(struct dlm_ls *ls)
 		list_add(&r->res_masters_list, &ls->ls_masters_list);
 		dlm_hold_rsb(r);
 	}
-	spin_unlock_bh(&ls->ls_rsbtbl_lock);
+	read_unlock_bh(&ls->ls_rsbtbl_lock);
  out:
 	write_unlock_bh(&ls->ls_masters_lock);
 	return error;
@@ -62,14 +62,14 @@ static void dlm_create_root_list(struct dlm_ls *ls, struct list_head *root_list)
 {
 	struct dlm_rsb *r;
 
-	spin_lock_bh(&ls->ls_rsbtbl_lock);
+	read_lock_bh(&ls->ls_rsbtbl_lock);
 	list_for_each_entry(r, &ls->ls_keep, res_rsbs_list) {
 		list_add(&r->res_root_list, root_list);
 		dlm_hold_rsb(r);
 	}
 
 	WARN_ON_ONCE(!list_empty(&ls->ls_toss));
-	spin_unlock_bh(&ls->ls_rsbtbl_lock);
+	read_unlock_bh(&ls->ls_rsbtbl_lock);
 }
 
 static void dlm_release_root_list(struct list_head *root_list)