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

diff --git a/fs/configfs/item.c b/fs/configfs/item.c
index 8b2a994042ddeb2d1b8c00bbee3436e79fff52ad..a66f6624d89943997d1d35ead214aee85857e5d7 100644 (file)
--- 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 a6ab012a2c6acf9815bb8d4d1e29fb4568084b08..c8aabba502f6d7f019890bcdeba2fcdd7a56717f 100644 (file)
--- 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,

diff --git a/include/linux/configfs.h b/include/linux/configfs.h
index 2319b8c108e87b9e87c11cc4c9aa314d24eb0364..c9670904968329ce3032825d55b28a72cb8b223c 100644 (file)
--- a/include/linux/configfs.h
+++ b/include/linux/configfs.h
@@ -74,7 +74,8 @@ extern void config_item_init_type_name(struct config_item *item,
                                       const char *name,
                                       struct config_item_type *type);
 
-extern struct config_item * config_item_get(struct config_item *);
+extern struct config_item *config_item_get(struct config_item *);
+extern struct config_item *config_item_get_unless_zero(struct config_item *);
 extern void config_item_put(struct config_item *);
 
 struct config_item_type {