Reads a specified block and returns the bh
struct buffer_head * __bread(struct block_device * bdev, sector_t block, unsigned size);
bdev
the block_device to read from
block
number of block
size
size (in bytes) to read
Reads a specified block, and returns buffer head that contains it. The page cache is allocated from movable area so that it can be migrated. It returns NULL if the block was unreadable.