Index: linux-stage/fs/ext4/ext4.h
===================================================================
--- linux-stage.orig/fs/ext4/ext4.h	2011-03-14 16:16:45.000000000 +0800
+++ linux-stage/fs/ext4/ext4.h	2011-03-14 16:17:08.732676431 +0800
@@ -758,7 +758,8 @@
 /*
  * Mount flags
  */
-#define EXT4_MOUNT_OLDALLOC		0x00002  /* Don't use the new Orlov allocator */
+#define EXT4_MOUNT_NO_MBCACHE		0x00001 /* Disable mbcache */
+#define EXT4_MOUNT_OLDALLOC		0x00002 /* Don't use the new Orlov allocator */
 #define EXT4_MOUNT_GRPID		0x00004	/* Create files with directory's group */
 #define EXT4_MOUNT_DEBUG		0x00008	/* Some debugging messages */
 #define EXT4_MOUNT_ERRORS_CONT		0x00010	/* Continue on errors */
Index: linux-stage/fs/ext4/super.c
===================================================================
--- linux-stage.orig/fs/ext4/super.c	2011-03-14 16:16:45.000000000 +0800
+++ linux-stage/fs/ext4/super.c	2011-03-14 16:18:13.831956469 +0800
@@ -1502,6 +1502,7 @@
 	Opt_inode_readahead_blks, Opt_journal_ioprio,
 	Opt_discard, Opt_nodiscard,
 	Opt_mballoc, Opt_bigendian_extents, Opt_force_over_16tb,
+	Opt_no_mbcache,
 	Opt_extents, Opt_noextents,
 };
 
@@ -1574,6 +1575,7 @@
 	{Opt_mballoc, "mballoc"},
 	{Opt_discard, "discard"},
 	{Opt_nodiscard, "nodiscard"},
+	{Opt_no_mbcache, "no_mbcache"},
 	{Opt_extents, "extents"},
 	{Opt_noextents, "noextents"},
 	{Opt_err, NULL},
@@ -2049,6 +2051,9 @@
 			}
 			clear_opt(sbi->s_mount_opt, EXTENTS);
 			break;
+		case Opt_no_mbcache:
+			set_opt(sbi->s_mount_opt, NO_MBCACHE);
+			break;
 		default:
 			ext4_msg(sb, KERN_ERR,
 			       "Unrecognized mount option \"%s\" "
Index: linux-stage/fs/ext4/xattr.c
===================================================================
--- linux-stage.orig/fs/ext4/xattr.c	2011-03-14 16:16:43.000000000 +0800
+++ linux-stage/fs/ext4/xattr.c	2011-03-14 16:17:08.806677883 +0800
@@ -86,7 +86,8 @@
 # define ea_bdebug(f...)
 #endif
 
-static void ext4_xattr_cache_insert(struct buffer_head *);
+static void ext4_xattr_cache_insert(struct super_block *,
+				    struct buffer_head *);
 static struct buffer_head *ext4_xattr_cache_find(struct inode *,
 						 struct ext4_xattr_header *,
 						 struct mb_cache_entry **);
@@ -234,7 +235,7 @@
 		error = -EIO;
 		goto cleanup;
 	}
-	ext4_xattr_cache_insert(bh);
+	ext4_xattr_cache_insert(inode->i_sb, bh);
 	entry = BFIRST(bh);
 	error = ext4_xattr_find_entry(&entry, name_index, name, bh->b_size, 1);
 	if (error == -EIO)
@@ -376,7 +377,7 @@
 		error = -EIO;
 		goto cleanup;
 	}
-	ext4_xattr_cache_insert(bh);
+	ext4_xattr_cache_insert(inode->i_sb, bh);
 	error = ext4_xattr_list_entries(inode, BFIRST(bh), buffer, buffer_size);
 
 cleanup:
@@ -473,7 +474,9 @@
 	struct mb_cache_entry *ce = NULL;
 	int error = 0;
 
-	ce = mb_cache_entry_get(ext4_xattr_cache, bh->b_bdev, bh->b_blocknr);
+	if (!test_opt(inode->i_sb, NO_MBCACHE))
+		ce = mb_cache_entry_get(ext4_xattr_cache, bh->b_bdev,
+					bh->b_blocknr);
 	error = ext4_journal_get_write_access(handle, bh);
 	if (error)
 		goto out;
@@ -700,8 +703,10 @@
 	if (i->value && i->value_len > sb->s_blocksize)
 		return -ENOSPC;
 	if (s->base) {
-		ce = mb_cache_entry_get(ext4_xattr_cache, bs->bh->b_bdev,
-					bs->bh->b_blocknr);
+		if (!test_opt(inode->i_sb, NO_MBCACHE))
+			ce = mb_cache_entry_get(ext4_xattr_cache,
+						bs->bh->b_bdev,
+						bs->bh->b_blocknr);
 		error = ext4_journal_get_write_access(handle, bs->bh);
 		if (error)
 			goto cleanup;
@@ -718,7 +723,7 @@
 				if (!IS_LAST_ENTRY(s->first))
 					ext4_xattr_rehash(header(s->base),
 							  s->here);
-				ext4_xattr_cache_insert(bs->bh);
+				ext4_xattr_cache_insert(sb, bs->bh);
 			}
 			unlock_buffer(bs->bh);
 			if (error == -EIO)
@@ -801,7 +806,8 @@
 				if (error)
 					goto cleanup_dquot;
 			}
-			mb_cache_entry_release(ce);
+			if (ce)
+				mb_cache_entry_release(ce);
 			ce = NULL;
 		} else if (bs->bh && s->base == bs->bh->b_data) {
 			/* We were modifying this block in-place. */
@@ -845,7 +851,7 @@
 			memcpy(new_bh->b_data, s->base, new_bh->b_size);
 			set_buffer_uptodate(new_bh);
 			unlock_buffer(new_bh);
-			ext4_xattr_cache_insert(new_bh);
+			ext4_xattr_cache_insert(sb, new_bh);
 			error = ext4_handle_dirty_metadata(handle,
 							   inode, new_bh);
 			if (error)
@@ -1403,12 +1409,15 @@
  * Returns 0, or a negative error number on failure.
  */
 static void
-ext4_xattr_cache_insert(struct buffer_head *bh)
+ext4_xattr_cache_insert(struct super_block *sb, struct buffer_head *bh)
 {
 	__u32 hash = le32_to_cpu(BHDR(bh)->h_hash);
 	struct mb_cache_entry *ce;
 	int error;
 
+	if (test_opt(sb, NO_MBCACHE))
+		return;
+
 	ce = mb_cache_entry_alloc(ext4_xattr_cache, GFP_NOFS);
 	if (!ce) {
 		ea_bdebug(bh, "out of memory");
@@ -1482,6 +1491,8 @@
 	__u32 hash = le32_to_cpu(header->h_hash);
 	struct mb_cache_entry *ce;
 
+	if (test_opt(inode->i_sb, NO_MBCACHE))
+		return NULL;
 	if (!header->h_hash)
 		return NULL;  /* never share */
 	ea_idebug(inode, "looking for cached blocks [%x]", (int)hash);