Index: linux-stage/fs/ext4/dir.c
===================================================================
--- linux-stage.orig/fs/ext4/dir.c	2011-04-19 01:02:34.000000000 +0800
+++ linux-stage/fs/ext4/dir.c	2011-04-19 01:24:36.000000000 +0800
@@ -242,22 +242,50 @@
	return ret;
 }

+static inline int is_32bit_api(void)
+{
+#ifdef HAVE_IS_COMPAT_TASK
+        return is_compat_task();
+#else
+        return (BITS_PER_LONG == 32);
+#endif
+}
+
 /*
  * These functions convert from the major/minor hash to an f_pos
  * value.
  *
- * Currently we only use major hash numer.  This is unfortunate, but
- * on 32-bit machines, the same VFS interface is used for lseek and
- * llseek, so if we use the 64 bit offset, then the 32-bit versions of
- * lseek/telldir/seekdir will blow out spectacularly, and from within
- * the ext2 low-level routine, we don't know if we're being called by
- * a 64-bit version of the system call or the 32-bit version of the
- * system call.  Worse yet, NFSv2 only allows for a 32-bit readdir
- * cookie.  Sigh.
+ * Up layer (OSD) should specify O_32BITHASH or O_64BITHASH explicitly.
+ * On the other hand, we allow ldiskfs to be mounted directly on both 32-bit
+ * and 64-bit nodes, under such case, neither O_32BITHASH nor O_64BITHASH is
+ * specified.
  */
-#define hash2pos(major, minor)	(major >> 1)
-#define pos2maj_hash(pos)	((pos << 1) & 0xffffffff)
-#define pos2min_hash(pos)	(0)
+static inline loff_t hash2pos(struct file *filp, __u32 major, __u32 minor)
+{
+	if ((filp->f_flags & O_32BITHASH) ||
+	    (!(filp->f_flags & O_64BITHASH) && is_32bit_api()))
+		return (major >> 1);
+	else
+		return (((__u64)(major >> 1) << 32) | (__u64)minor);
+}
+
+static inline __u32 pos2maj_hash(struct file *filp, loff_t pos)
+{
+	if ((filp->f_flags & O_32BITHASH) ||
+	    (!(filp->f_flags & O_64BITHASH) && is_32bit_api()))
+		return ((pos << 1) & 0xffffffff);
+	else
+		return (((pos >> 32) << 1) & 0xffffffff);
+}
+
+static inline __u32 pos2min_hash(struct file *filp, loff_t pos)
+{
+	if ((filp->f_flags & O_32BITHASH) ||
+	    (!(filp->f_flags & O_64BITHASH) && is_32bit_api()))
+		return (0);
+	else
+		return (pos & 0xffffffff);
+}
 
 /*
  * This structure holds the nodes of the red-black tree used to store
@@ -318,15 +346,16 @@
 }
 
 
-static struct dir_private_info *ext4_htree_create_dir_info(loff_t pos)
+static struct dir_private_info *
+ext4_htree_create_dir_info(struct file *filp, loff_t pos)
 {
 	struct dir_private_info *p;
 
 	p = kzalloc(sizeof(struct dir_private_info), GFP_KERNEL);
 	if (!p)
 		return NULL;
-	p->curr_hash = pos2maj_hash(pos);
-	p->curr_minor_hash = pos2min_hash(pos);
+	p->curr_hash = pos2maj_hash(filp, pos);
+	p->curr_minor_hash = pos2min_hash(filp, pos);
 	return p;
 }
 
@@ -422,7 +451,7 @@
 		       "null fname?!?\n");
 		return 0;
 	}
-	curr_pos = hash2pos(fname->hash, fname->minor_hash);
+	curr_pos = hash2pos(filp, fname->hash, fname->minor_hash);
 	while (fname) {
 		error = filldir(dirent, fname->name,
 				fname->name_len, curr_pos,
@@ -447,7 +476,7 @@
 	int	ret;
 
 	if (!info) {
-		info = ext4_htree_create_dir_info(filp->f_pos);
+		info = ext4_htree_create_dir_info(filp, filp->f_pos);
 		if (!info)
 			return -ENOMEM;
 		filp->private_data = info;
@@ -461,8 +490,8 @@
 		free_rb_tree_fname(&info->root);
 		info->curr_node = NULL;
 		info->extra_fname = NULL;
-		info->curr_hash = pos2maj_hash(filp->f_pos);
-		info->curr_minor_hash = pos2min_hash(filp->f_pos);
+		info->curr_hash = pos2maj_hash(filp, filp->f_pos);
+		info->curr_minor_hash = pos2min_hash(filp, filp->f_pos);
 	}
 
 	/*
Index: linux-stage/fs/ext4/ext4.h
===================================================================
--- linux-stage.orig/fs/ext4/ext4.h	2011-04-19 01:02:34.000000000 +0800
+++ linux-stage/fs/ext4/ext4.h	2011-04-19 01:02:34.000000000 +0800
@@ -55,6 +55,14 @@
 #define ext4_debug(f, a...)	do {} while (0)
 #endif
 
+#ifndef O_32BITHASH
+# define O_32BITHASH	0x10000000
+#endif
+
+#ifndef O_64BITHASH
+# define O_64BITHASH	0x20000000
+#endif
+
 #define HAVE_DISK_INODE_VERSION
 
 /* data type for block offset of block group */