if (!buffer_uptodate(bh))
if (likely(bh) && !buffer_uptodate(bh))
__bread(struct block_device *bdev, sector_t block, int size){	struct buffer_head *bh = __getblk(bdev, block, size);	if (!buffer_uptodate(bh))		bh = __bread_slow(bh);	return bh;}