[PATCH] pass b_size to ->get_block()

Pass amount of disk needs to be mapped to get_block().  This way one can
modify the fs ->get_block() functions to map multiple blocks at the same time.

[akpm@osdl.org: performance tweak]
[akpm@osdl.org: remove unneeded assignments]
Signed-off-by: NBadari Pulavarty <pbadari@us.ibm.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

fs/buffer.c

@@ -1738,6 +1738,7 @@ static int __block_write_full_page(struct inode *inode, struct page *page,
 	sector_t block;
 	sector_t last_block;
 	struct buffer_head *bh, *head;
+	const unsigned blocksize = 1 << inode->i_blkbits;
 	int nr_underway = 0;
 
 	BUG_ON(!PageLocked(page));
@@ -1745,7 +1746,7 @@ static int __block_write_full_page(struct inode *inode, struct page *page,
 	last_block = (i_size_read(inode) - 1) >> inode->i_blkbits;
 
 	if (!page_has_buffers(page)) {
-		create_empty_buffers(page, 1 << inode->i_blkbits,
+		create_empty_buffers(page, blocksize,
 					(1 << BH_Dirty)|(1 << BH_Uptodate));
 	}
 
@@ -1780,6 +1781,7 @@ static int __block_write_full_page(struct inode *inode, struct page *page,
 			clear_buffer_dirty(bh);
 			set_buffer_uptodate(bh);
 		} else if (!buffer_mapped(bh) && buffer_dirty(bh)) {
+			WARN_ON(bh->b_size != blocksize);
 			err = get_block(inode, block, bh, 1);
 			if (err)
 				goto recover;
@@ -1933,6 +1935,7 @@ static int __block_prepare_write(struct inode *inode, struct page *page,
 		if (buffer_new(bh))
 			clear_buffer_new(bh);
 		if (!buffer_mapped(bh)) {
+			WARN_ON(bh->b_size != blocksize);
 			err = get_block(inode, block, bh, 1);
 			if (err)
 				break;
@@ -2088,6 +2091,7 @@ int block_read_full_page(struct page *page, get_block_t *get_block)
 
 			fully_mapped = 0;
 			if (iblock < lblock) {
+				WARN_ON(bh->b_size != blocksize);
 				err = get_block(inode, iblock, bh, 0);
 				if (err)
 					SetPageError(page);
@@ -2409,6 +2413,7 @@ int nobh_prepare_write(struct page *page, unsigned from, unsigned to,
 		create = 1;
 		if (block_start >= to)
 			create = 0;
+		map_bh.b_size = blocksize;
 		ret = get_block(inode, block_in_file + block_in_page,
 					&map_bh, create);
 		if (ret)
@@ -2669,6 +2674,7 @@ int block_truncate_page(struct address_space *mapping,
 
 	err = 0;
 	if (!buffer_mapped(bh)) {
+		WARN_ON(bh->b_size != blocksize);
 		err = get_block(inode, iblock, bh, 0);
 		if (err)
 			goto unlock;
@@ -2755,6 +2761,7 @@ sector_t generic_block_bmap(struct address_space *mapping, sector_t block,
 	struct inode *inode = mapping->host;
 	tmp.b_state = 0;
 	tmp.b_blocknr = 0;
+	tmp.b_size = 1 << inode->i_blkbits;
 	get_block(inode, block, &tmp, 0);
 	return tmp.b_blocknr;
 }

fs/mpage.c

@@ -192,6 +192,7 @@ do_mpage_readpage(struct bio *bio, struct page *page, unsigned nr_pages,
 				page_block++, block_in_file++) {
 		bh.b_state = 0;
 		if (block_in_file < last_block) {
+			bh.b_size = blocksize;
 			if (get_block(inode, block_in_file, &bh, 0))
 				goto confused;
 		}
@@ -472,6 +473,7 @@ __mpage_writepage(struct bio *bio, struct page *page, get_block_t get_block,
 	for (page_block = 0; page_block < blocks_per_page; ) {
 
 		map_bh.b_state = 0;
+		map_bh.b_size = 1 << blkbits;
 		if (get_block(inode, block_in_file, &map_bh, 1))
 			goto confused;
 		if (buffer_new(&map_bh))

include/linux/buffer_head.h

@@ -280,6 +280,7 @@ map_bh(struct buffer_head *bh, struct super_block *sb, sector_t block)
 	set_buffer_mapped(bh);
 	bh->b_bdev = sb->s_bdev;
 	bh->b_blocknr = block;
+	bh->b_size = sb->s_blocksize;
 }
 
 /*