[Cluster-devel] [PATCH v1 08/11] locks: convert fl_link to a hlist_node

[Jeff Layton <jlayton@redhat.com>]

Testing has shown that iterating over the blocked_list for deadlock
detection turns out to be a bottleneck. In order to alleviate that,
begin the process of turning it into a hashtable. We start by turning
the fl_link into a hlist_node and the global lists into hlists. A later
patch will do the conversion of the blocked_list to a hashtable.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
---
 fs/locks.c         |   32 ++++++++++++++++----------------
 include/linux/fs.h |    2 +-
 2 files changed, 17 insertions(+), 17 deletions(-)

diff --git a/fs/locks.c b/fs/locks.c
index fc35b9e..5ed056b 100644
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -163,8 +163,8 @@ int lease_break_time = 45;
 #define for_each_lock(inode, lockp) \
 	for (lockp = &inode->i_flock; *lockp != NULL; lockp = &(*lockp)->fl_next)
 
-static LIST_HEAD(file_lock_list);
-static LIST_HEAD(blocked_list);
+static HLIST_HEAD(file_lock_list);
+static HLIST_HEAD(blocked_list);
 
 /* Protects the two list heads above */
 static DEFINE_SPINLOCK(file_lock_lock);
@@ -173,7 +173,7 @@ static struct kmem_cache *filelock_cache __read_mostly;
 
 static void locks_init_lock_heads(struct file_lock *fl)
 {
-	INIT_LIST_HEAD(&fl->fl_link);
+	INIT_HLIST_NODE(&fl->fl_link);
 	INIT_LIST_HEAD(&fl->fl_block);
 	init_waitqueue_head(&fl->fl_wait);
 }
@@ -207,7 +207,7 @@ void locks_free_lock(struct file_lock *fl)
 {
 	BUG_ON(waitqueue_active(&fl->fl_wait));
 	BUG_ON(!list_empty(&fl->fl_block));
-	BUG_ON(!list_empty(&fl->fl_link));
+	BUG_ON(!hlist_unhashed(&fl->fl_link));
 
 	locks_release_private(fl);
 	kmem_cache_free(filelock_cache, fl);
@@ -486,7 +486,7 @@ static inline void
 locks_insert_global_blocked(struct file_lock *waiter)
 {
 	spin_lock(&file_lock_lock);
-	list_add(&waiter->fl_link, &blocked_list);
+	hlist_add_head(&waiter->fl_link, &blocked_list);
 	spin_unlock(&file_lock_lock);
 }
 
@@ -494,7 +494,7 @@ static inline void
 locks_delete_global_blocked(struct file_lock *waiter)
 {
 	spin_lock(&file_lock_lock);
-	list_del_init(&waiter->fl_link);
+	hlist_del_init(&waiter->fl_link);
 	spin_unlock(&file_lock_lock);
 }
 
@@ -502,7 +502,7 @@ static inline void
 locks_insert_global_locks(struct file_lock *waiter)
 {
 	spin_lock(&file_lock_lock);
-	list_add_tail(&waiter->fl_link, &file_lock_list);
+	hlist_add_head(&waiter->fl_link, &file_lock_list);
 	spin_unlock(&file_lock_lock);
 }
 
@@ -510,7 +510,7 @@ static inline void
 locks_delete_global_locks(struct file_lock *waiter)
 {
 	spin_lock(&file_lock_lock);
-	list_del_init(&waiter->fl_link);
+	hlist_del_init(&waiter->fl_link);
 	spin_unlock(&file_lock_lock);
 }
 
@@ -705,7 +705,7 @@ static struct file_lock *what_owner_is_waiting_for(struct file_lock *block_fl)
 {
 	struct file_lock *fl, *ret = NULL;
 
-	list_for_each_entry(fl, &blocked_list, fl_link) {
+	hlist_for_each_entry(fl, &blocked_list, fl_link) {
 		if (posix_same_owner(fl, block_fl)) {
 			ret = fl->fl_next;
 			if (likely(ret))
@@ -867,7 +867,7 @@ static int __posix_lock_file(struct inode *inode, struct file_lock *request, str
 				goto out;
 			error = FILE_LOCK_DEFERRED;
 			locks_insert_block(fl, request);
-			if (list_empty(&request->fl_link))
+			if (hlist_unhashed(&request->fl_link))
 				locks_insert_global_blocked(request);
 			goto out;
   		}
@@ -882,10 +882,10 @@ static int __posix_lock_file(struct inode *inode, struct file_lock *request, str
 	 * Now that we know the request is no longer blocked, we can take it
 	 * off the global list. Some callers send down partially initialized
 	 * requests, so we only do this if FL_SLEEP is set. Also, avoid taking
-	 * the lock if the list is empty, as that indicates a request that
+	 * the lock if the hlist is unhashed, as that indicates a request that
 	 * never blocked.
 	 */
-	if ((request->fl_flags & FL_SLEEP) && !list_empty(&request->fl_link))
+	if ((request->fl_flags & FL_SLEEP) && !hlist_unhashed(&request->fl_link))
 		locks_delete_global_blocked(request);
 
 	/*
@@ -2277,11 +2277,11 @@ static int locks_show(struct seq_file *f, void *v)
 {
 	struct file_lock *fl, *bfl;
 
-	fl = list_entry(v, struct file_lock, fl_link);
+	fl = hlist_entry(v, struct file_lock, fl_link);
 
 	lock_get_status(f, fl, *((loff_t *)f->private), "");
 
-	list_for_each_entry(bfl, &blocked_list, fl_link) {
+	hlist_for_each_entry(bfl, &blocked_list, fl_link) {
 		if (bfl->fl_next == fl)
 			lock_get_status(f, bfl, *((loff_t *)f->private), " ->");
 	}
@@ -2295,14 +2295,14 @@ static void *locks_start(struct seq_file *f, loff_t *pos)
 
 	spin_lock(&file_lock_lock);
 	*p = (*pos + 1);
-	return seq_list_start(&file_lock_list, *pos);
+	return seq_hlist_start(&file_lock_list, *pos);
 }
 
 static void *locks_next(struct seq_file *f, void *v, loff_t *pos)
 {
 	loff_t *p = f->private;
 	++*p;
-	return seq_list_next(v, &file_lock_list, pos);
+	return seq_hlist_next(v, &file_lock_list, pos);
 }
 
 static void locks_stop(struct seq_file *f, void *v)
diff --git a/include/linux/fs.h b/include/linux/fs.h
index ccb44ea..07a009e 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -934,7 +934,7 @@ int locks_in_grace(struct net *);
  */
 struct file_lock {
 	struct file_lock *fl_next;	/* singly linked list for this inode  */
-	struct list_head fl_link;	/* doubly linked list of all locks */
+	struct hlist_node fl_link;	/* node in global lists */
 	struct list_head fl_block;	/* circular list of blocked processes */
 	fl_owner_t fl_owner;
 	unsigned int fl_flags;
-- 
1.7.1