Merge remote-tracking branch 'asoc/topic/component' into asoc-next

[linux-2.6-microblaze.git] / fs / kernfs / mount.c

diff --git a/fs/kernfs/mount.c b/fs/kernfs/mount.c
index d171b98..f973ae9 100644 (file)
--- a/fs/kernfs/mount.c
+++ b/fs/kernfs/mount.c
@@ -211,6 +211,36 @@ void kernfs_kill_sb(struct super_block *sb)
        kernfs_put(root_kn);
 }
 
+/**
+ * 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)
 {
        kernfs_node_cache = kmem_cache_create("kernfs_node_cache",