vfs: new d_init method

Allow filesystem to initialize dentry at allocation time.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/dcache.c b/fs/dcache.c
index d5beef0..6d60a76 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -1569,6 +1569,7 @@
 {
 	struct dentry *dentry;
 	char *dname;
+	int err;
 
 	dentry = kmem_cache_alloc(dentry_cache, GFP_KERNEL);
 	if (!dentry)
@@ -1627,6 +1628,16 @@
 	INIT_LIST_HEAD(&dentry->d_child);
 	d_set_d_op(dentry, dentry->d_sb->s_d_op);
 
+	if (dentry->d_op && dentry->d_op->d_init) {
+		err = dentry->d_op->d_init(dentry);
+		if (err) {
+			if (dname_external(dentry))
+				kfree(external_name(dentry));
+			kmem_cache_free(dentry_cache, dentry);
+			return NULL;
+		}
+	}
+
 	this_cpu_inc(nr_dentry);
 
 	return dentry;