ext4 块读取ext4_bread

ext4_bread

struct buffer_head *ext4_bread(handle_t *handle, struct inode *inode,       ext4_lblk_t block, int map_flags){struct buffer_head *bh;bh = ext4_getblk(handle, inode, block, map_flags);if (IS_ERR(bh))return bh;if (!bh || buffer_uptodate(bh))return bh;ll_rw_block(REQ_OP_READ, REQ_META | REQ_PRIO, 1, &bh);wait_on_buffer(bh);if (buffer_uptodate(bh))return bh;put_bh(bh);return ERR_PTR(-EIO);}