Index: linux-2.6.27.21-0.1/fs/ext4/super.c
===================================================================
--- linux-2.6.27.21-0.1.orig/fs/ext4/super.c
+++ linux-2.6.27.21-0.1/fs/ext4/super.c
@@ -74,6 +74,8 @@ static void ext4_write_super_lockfs(stru
 
 struct proc_dir_entry *proc_root_ext4;
 
+static int bigendian_extents;
+
 ext4_fsblk_t ext4_block_bitmap(struct super_block *sb,
 			       struct ext4_group_desc *bg)
 {
@@ -1291,7 +1293,7 @@ enum {
	Opt_stripe, Opt_delalloc, Opt_nodelalloc,
	Opt_block_validity, Opt_noblock_validity,
	Opt_inode_readahead_blks, Opt_journal_ioprio,
-	Opt_discard, Opt_nodiscard,
+	Opt_discard, Opt_nodiscard, Opt_bigendian_extents,
 	Opt_iopen, Opt_noiopen, Opt_iopen_nopriv,
 };
 
@@ -1353,6 +1355,7 @@ static const match_table_t tokens = {
	{Opt_noauto_da_alloc, "noauto_da_alloc"},
	{Opt_discard, "discard"},
	{Opt_nodiscard, "nodiscard"},
+	{Opt_bigendian_extents, "bigendian_extents"},
 	{Opt_err, NULL},
 };
 
@@ -1768,6 +1771,9 @@ set_qf_format:
		case Opt_nodiscard:
			clear_opt(sbi->s_mount_opt, DISCARD);
 			break;
+		case Opt_bigendian_extents:
+			bigendian_extents = 1;
+			break;
 		default:
			ext4_msg(sb, KERN_ERR,
			       "Unrecognized mount option \"%s\" "
@@ -2673,6 +2679,15 @@ static int ext4_fill_super(struct super_
 				 &sbi->s_inode_readahead_blks);
 #endif
 
+#ifdef __BIG_ENDIAN
+	if (bigendian_extents == 0) {
+		printk(KERN_ERR "EXT4-fs: extents feature is not guaranteed to "
+		       "work on big-endian systems. Use \"bigendian_extents\" "
+		       "mount option to override.\n");
+		goto failed_mount;
+	}
+#endif
+
 	bgl_lock_init(sbi->s_blockgroup_lock);
 
	for (i = 0; i < db_count; i++) {