Index: linux-2.6.31-rc5/drivers/mtd/devices/block2mtd.c
===================================================================
--- linux-2.6.31-rc5.orig/drivers/mtd/devices/block2mtd.c	2009-08-03 16:33:55.846298216 +0900
+++ linux-2.6.31-rc5/drivers/mtd/devices/block2mtd.c	2009-08-03 16:34:29.986318468 +0900
@@ -24,6 +24,7 @@
 #define ERROR(fmt, args...) printk(KERN_ERR "block2mtd: " fmt "\n" , ## args)
 #define INFO(fmt, args...) printk(KERN_INFO "block2mtd: " fmt "\n" , ## args)
 
+#define MTD_PAGE_MASK (~((loff_t)(PAGE_SIZE-1)))
 
 /* Info for the block device */
 struct block2mtd_dev {
@@ -149,7 +150,7 @@
 	struct page *page;
 	struct address_space *mapping = dev->blkdev->bd_inode->i_mapping;
 	int index = to >> PAGE_SHIFT;	// page index
-	int offset = to & ~PAGE_MASK;	// page offset
+	int offset = to & ~MTD_PAGE_MASK;	// page offset
 	int cpylen;
 
 	if (retlen)
@@ -286,7 +287,7 @@
 	sprintf(name, "block2mtd: %s", devname);
 	dev->mtd.name = name;
 
-	dev->mtd.size = dev->blkdev->bd_inode->i_size & PAGE_MASK;
+	dev->mtd.size = dev->blkdev->bd_inode->i_size & MTD_PAGE_MASK;
 	dev->mtd.erasesize = erase_size;
 	dev->mtd.writesize = 1;
 	dev->mtd.type = MTD_RAM;