Add a mount option to turn off extents.

Signed-Off-By: Mingming Cao <cmm@us.ibm.com>
---
Index: linux-2.6.21-rc7/fs/ext4/super.c
===================================================================
--- linux-2.6.21-rc7.orig/fs/ext4/super.c	2007-04-17 18:04:27.000000000 -0700
+++ linux-2.6.21-rc7/fs/ext4/super.c	2007-04-17 18:04:44.000000000 -0700
@@ -728,7 +728,7 @@
 	Opt_usrjquota, Opt_grpjquota, Opt_offusrjquota, Opt_offgrpjquota,
 	Opt_jqfmt_vfsold, Opt_jqfmt_vfsv0, Opt_quota, Opt_noquota,
 	Opt_ignore, Opt_barrier, Opt_err, Opt_resize, Opt_usrquota,
-	Opt_grpquota, Opt_extents,
+	Opt_grpquota, Opt_extents, Opt_noextents,
 };
 
 static match_table_t tokens = {
@@ -779,6 +779,7 @@
 	{Opt_usrquota, "usrquota"},
 	{Opt_barrier, "barrier=%u"},
 	{Opt_extents, "extents"},
+	{Opt_noextents, "noextents"},
 	{Opt_err, NULL},
 	{Opt_resize, "resize"},
 };
@@ -1114,6 +1115,9 @@
 		case Opt_extents:
 			set_opt (sbi->s_mount_opt, EXTENTS);
 			break;
+		case Opt_noextents:
+			clear_opt (sbi->s_mount_opt, EXTENTS);
+			break;
 		default:
 			printk (KERN_ERR
 				"EXT4-fs: Unrecognized mount option \"%s\" "