1 files changed, 24 insertions, 0 deletions

diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
index 3cf8a15af916..345fc89c4286 100644
--- a/fs/cifs/cifsfs.c
+++ b/fs/cifs/cifsfs.c
@@ -91,6 +91,30 @@ struct workqueue_struct	*cifsiod_wq;
 __u8 cifs_client_guid[SMB2_CLIENT_GUID_SIZE];
 #endif
 
+/*
+ * Bumps refcount for cifs super block.
+ * Note that it should be only called if a referece to VFS super block is
+ * already held, e.g. in open-type syscalls context. Otherwise it can race with
+ * atomic_dec_and_test in deactivate_locked_super.
+ */
+void
+cifs_sb_active(struct super_block *sb)
+{
+        struct cifs_sb_info *server = CIFS_SB(sb);
+
+        if (atomic_inc_return(&server->active) == 1)
+                atomic_inc(&sb->s_active);
+}
+
+void
+cifs_sb_deactive(struct super_block *sb)
+{
+        struct cifs_sb_info *server = CIFS_SB(sb);
+
+        if (atomic_dec_and_test(&server->active))
+                deactivate_super(sb);
+}
+
 static int
 cifs_read_super(struct super_block *sb)
 {