Merge tag 'configfs-for-4.12' of git://git.infradead.org/users/hch/configfs

Pull configfs updates from Christoph Hellwig:
 "A fix from Nic for a race seen in production (including a stable tag).

  And while I'm sending you this I'm also sneaking in a trivial new
  helper from Bart so that we don't need inter-tree dependencies for the
  next merge window"

* tag 'configfs-for-4.12' of git://git.infradead.org/users/hch/configfs:
  configfs: Introduce config_item_get_unless_zero()
  configfs: Fix race between create_link and configfs_rmdir

2 files changed, 9 insertions, 2 deletions

diff --git a/fs/configfs/item.c b/fs/configfs/item.c
index 8b2a994042dd..a66f6624d899 100644
--- a/fs/configfs/item.c
+++ b/fs/configfs/item.c
@@ -138,6 +138,14 @@ struct config_item *config_item_get(struct config_item *item)
 }
 EXPORT_SYMBOL(config_item_get);
 
+struct config_item *config_item_get_unless_zero(struct config_item *item)
+{
+        if (item && kref_get_unless_zero(&item->ci_kref))
+                return item;
+        return NULL;
+}
+EXPORT_SYMBOL(config_item_get_unless_zero);
+
 static void config_item_cleanup(struct config_item *item)
 {
         struct config_item_type *t = item->ci_type;
diff --git a/fs/configfs/symlink.c b/fs/configfs/symlink.c
index a6ab012a2c6a..c8aabba502f6 100644
--- a/fs/configfs/symlink.c
+++ b/fs/configfs/symlink.c
@@ -83,14 +83,13 @@ static int create_link(struct config_item *parent_item,
         ret = -ENOMEM;
         sl = kmalloc(sizeof(struct configfs_symlink), GFP_KERNEL);
         if (sl) {
-                sl->sl_target = config_item_get(item);
                 spin_lock(&configfs_dirent_lock);
                 if (target_sd->s_type & CONFIGFS_USET_DROPPING) {
                         spin_unlock(&configfs_dirent_lock);
-                        config_item_put(item);
                         kfree(sl);
                         return -ENOENT;
                 }
+                sl->sl_target = config_item_get(item);
                 list_add(&sl->sl_list, &target_sd->s_links);
                 spin_unlock(&configfs_dirent_lock);
                 ret = configfs_create_link(sl, parent_item->ci_dentry,