Btrfs: fix number of transaction units required to create symlink

BugLink: http://bugs.launchpad.net/bugs/1553179

commit 9269d12b upstream.

We weren't accounting for the insertion of an inline extent item for the
symlink inode nor that we need to update the parent inode item (through
the call to btrfs_add_nondir()). So fix this by including two more
transaction units.
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>

fs/btrfs/inode.c

@@ -9663,9 +9663,11 @@ static int btrfs_symlink(struct inode *dir, struct dentry *dentry,
 	/*
 	 * 2 items for inode item and ref
 	 * 2 items for dir items
+	 * 1 item for updating parent inode item
+	 * 1 item for the inline extent item
 	 * 1 item for xattr if selinux is on
 	 */
-	trans = btrfs_start_transaction(root, 5);
+	trans = btrfs_start_transaction(root, 7);
 	if (IS_ERR(trans))
 		return PTR_ERR(trans);