Poision new and !uptodate buffers.

Index: linux-2.6/fs/buffer.c
===================================================================
--- linux-2.6.orig/fs/buffer.c
+++ linux-2.6/fs/buffer.c
@@ -1562,6 +1562,15 @@ void unmap_underlying_metadata(struct bl
 }
 EXPORT_SYMBOL(unmap_underlying_metadata);
 
+static void poison_new_buffer(struct page *page, struct buffer_head *bh, int nr, int blocksize)
+{
+	if (buffer_new(bh) && !buffer_uptodate(bh)) {
+		void *kaddr = kmap_atomic(page, KM_USER0);
+		memset(kaddr + nr*blocksize, 0x0f, blocksize);
+		kunmap_atomic(kaddr, KM_USER0);
+	}
+}
+
 /*
  * NOTE! All mapped/uptodate combinations are valid:
  *
@@ -1592,6 +1601,7 @@ static int __block_write_full_page(struc
 {
 	int err;
 	sector_t block;
+	int i = 0;
 	sector_t last_block;
 	struct buffer_head *bh, *head;
 	const unsigned blocksize = 1 << inode->i_blkbits;
@@ -1641,6 +1651,7 @@ static int __block_write_full_page(struc
 			err = get_block(inode, block, bh, 1);
 			if (err)
 				goto recover;
+			poison_new_buffer(page, bh, i, blocksize);
 			if (buffer_new(bh)) {
 				/* blockdev mappings never come here */
 				clear_buffer_new(bh);
@@ -1650,6 +1661,7 @@ static int __block_write_full_page(struc
 		}
 		bh = bh->b_this_page;
 		block++;
+		i++;
 	} while (bh != head);
 
 	do {
@@ -1808,6 +1820,7 @@ static int __block_prepare_write(struct 
 	unsigned block_start, block_end;
 	sector_t block;
 	int err = 0;
+	int i = 0;
 	unsigned blocksize, bbits;
 	struct buffer_head *bh, *head, *wait[2], **wait_bh=wait;
 
@@ -1825,7 +1838,7 @@ static int __block_prepare_write(struct 
 	block = (sector_t)page->index << (PAGE_CACHE_SHIFT - bbits);
 
 	for(bh = head, block_start = 0; bh != head || !block_start;
-	    block++, block_start=block_end, bh = bh->b_this_page) {
+	    block++, i++, block_start=block_end, bh = bh->b_this_page) {
 		block_end = block_start + blocksize;
 		if (block_end <= from || block_start >= to) {
 			if (PageUptodate(page)) {
@@ -1841,6 +1854,7 @@ static int __block_prepare_write(struct 
 			err = get_block(inode, block, bh, 1);
 			if (err)
 				break;
+			poison_new_buffer(page, bh, i, blocksize);
 			if (buffer_new(bh)) {
 				unmap_underlying_metadata(bh->b_bdev,
 							bh->b_blocknr);
@@ -2087,6 +2101,7 @@ int block_read_full_page(struct page *pa
 				err = get_block(inode, iblock, bh, 0);
 				if (err)
 					SetPageError(page);
+				poison_new_buffer(page, bh, i, blocksize);
 			}
 			if (!buffer_mapped(bh)) {
 				void *kaddr = kmap_atomic(page, KM_USER0);
@@ -2404,6 +2419,7 @@ int nobh_prepare_write(struct page *page
 					&map_bh, create);
 		if (ret)
 			goto failed;
+		poison_new_buffer(page, &map_bh, block_in_page, blocksize);
 		if (!buffer_mapped(&map_bh))
 			is_mapped_to_disk = 0;
 		if (buffer_new(&map_bh))
@@ -2619,7 +2635,7 @@ int block_truncate_page(struct address_s
 	pgoff_t index = from >> PAGE_CACHE_SHIFT;
 	unsigned offset = from & (PAGE_CACHE_SIZE-1);
 	unsigned blocksize;
-	sector_t iblock;
+	sector_t iblock, i;
 	unsigned length, pos;
 	struct inode *inode = mapping->host;
 	struct page *page;
@@ -2648,8 +2664,10 @@ int block_truncate_page(struct address_s
 	/* Find the buffer that contains "offset" */
 	bh = page_buffers(page);
 	pos = blocksize;
+	i = 0;
 	while (offset >= pos) {
 		bh = bh->b_this_page;
+		i++;
 		iblock++;
 		pos += blocksize;
 	}
@@ -2660,6 +2678,7 @@ int block_truncate_page(struct address_s
 		err = get_block(inode, iblock, bh, 0);
 		if (err)
 			goto unlock;
+		poison_new_buffer(page, bh, i, blocksize);
 		/* unmapped? It's a hole - nothing to do */
 		if (!buffer_mapped(bh))
 			goto unlock;