[RFC PATCH v6 1/4] dcache: export shrink_dentry_list() and add new helper d_dispose_if_unused()

[Luis Henriques <luis@igalia.com>]

Add and export a new helper d_dispose_if_unused() which is simply a wrapper
around to_shrink_list(), to add an entry to a dispose list if it's not used
anymore.

Also export shrink_dentry_list() to kill all dentries in a dispose list.

Suggested-by: Miklos Szeredi <miklos@szeredi.hu>
Signed-off-by: Luis Henriques <luis@igalia.com>
---
 fs/dcache.c            | 18 ++++++++++++------
 include/linux/dcache.h |  2 ++
 2 files changed, 14 insertions(+), 6 deletions(-)

diff --git a/fs/dcache.c b/fs/dcache.c
index 60046ae23d51..3adefe05583c 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -1086,6 +1086,15 @@ struct dentry *d_find_alias_rcu(struct inode *inode)
 	return de;
 }
 
+void d_dispose_if_unused(struct dentry *dentry, struct list_head *dispose)
+{
+	spin_lock(&dentry->d_lock);
+	if (!dentry->d_lockref.count)
+		to_shrink_list(dentry, dispose);
+	spin_unlock(&dentry->d_lock);
+}
+EXPORT_SYMBOL(d_dispose_if_unused);
+
 /*
  *	Try to kill dentries associated with this inode.
  * WARNING: you must own a reference to inode.
@@ -1096,12 +1105,8 @@ void d_prune_aliases(struct inode *inode)
 	struct dentry *dentry;
 
 	spin_lock(&inode->i_lock);
-	hlist_for_each_entry(dentry, &inode->i_dentry, d_u.d_alias) {
-		spin_lock(&dentry->d_lock);
-		if (!dentry->d_lockref.count)
-			to_shrink_list(dentry, &dispose);
-		spin_unlock(&dentry->d_lock);
-	}
+	hlist_for_each_entry(dentry, &inode->i_dentry, d_u.d_alias)
+		d_dispose_if_unused(dentry, &dispose);
 	spin_unlock(&inode->i_lock);
 	shrink_dentry_list(&dispose);
 }
@@ -1141,6 +1146,7 @@ void shrink_dentry_list(struct list_head *list)
 		shrink_kill(dentry);
 	}
 }
+EXPORT_SYMBOL(shrink_dentry_list);
 
 static enum lru_status dentry_lru_isolate(struct list_head *item,
 		struct list_lru_one *lru, void *arg)
diff --git a/include/linux/dcache.h b/include/linux/dcache.h
index cc3e1c1a3454..4ef41a5debdc 100644
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -265,6 +265,8 @@ extern void d_tmpfile(struct file *, struct inode *);
 
 extern struct dentry *d_find_alias(struct inode *);
 extern void d_prune_aliases(struct inode *);
+extern void d_dispose_if_unused(struct dentry *, struct list_head *);
+extern void shrink_dentry_list(struct list_head *);
 
 extern struct dentry *d_find_alias_rcu(struct inode *);