kill kernfs_pin_sb()

unused now and impossible to use safely anyway.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/kernfs/mount.c

@@ -377,36 +377,6 @@ void kernfs_kill_sb(struct super_block *sb)
 	kfree(info);
 }
 
-/**
- * kernfs_pin_sb: try to pin the superblock associated with a kernfs_root
- * @kernfs_root: the kernfs_root in question
- * @ns: the namespace tag
- *
- * Pin the superblock so the superblock won't be destroyed in subsequent
- * operations.  This can be used to block ->kill_sb() which may be useful
- * for kernfs users which dynamically manage superblocks.
- *
- * Returns NULL if there's no superblock associated to this kernfs_root, or
- * -EINVAL if the superblock is being freed.
- */
-struct super_block *kernfs_pin_sb(struct kernfs_root *root, const void *ns)
-{
-	struct kernfs_super_info *info;
-	struct super_block *sb = NULL;
-
-	mutex_lock(&kernfs_mutex);
-	list_for_each_entry(info, &root->supers, node) {
-		if (info->ns == ns) {
-			sb = info->sb;
-			if (!atomic_inc_not_zero(&info->sb->s_active))
-				sb = ERR_PTR(-EINVAL);
-			break;
-		}
-	}
-	mutex_unlock(&kernfs_mutex);
-	return sb;
-}
-
 void __init kernfs_init(void)
 {
 

include/linux/kernfs.h

@@ -357,7 +357,6 @@ struct dentry *kernfs_mount_ns(struct file_system_type *fs_type, int flags,
 			       struct kernfs_root *root, unsigned long magic,
 			       bool *new_sb_created, const void *ns);
 void kernfs_kill_sb(struct super_block *sb);
-struct super_block *kernfs_pin_sb(struct kernfs_root *root, const void *ns);
 
 void kernfs_init(void);