ext4: Handle nested ext4_journal_start/stop calls without a journal

This patch fixes a problem with handling nested calls to
ext4_journal_start/ext4_journal_stop, when there is no journal present.

Signed-off-by: Curt Wohlgemuth <curtw@google.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
index 42f81d2..7c8fe80 100644
--- a/fs/ext4/namei.c
+++ b/fs/ext4/namei.c
@@ -2076,7 +2076,8 @@
 	struct ext4_iloc iloc;
 	int err = 0;
 
-	if (!ext4_handle_valid(handle))
+	/* ext4_handle_valid() assumes a valid handle_t pointer */
+	if (handle && !ext4_handle_valid(handle))
 		return 0;
 
 	mutex_lock(&EXT4_SB(inode->i_sb)->s_orphan_lock);