Man page 9 : ll_rw_block

ll_rw_block - level access to block devices (DEPRECATED)

void ll_rw_block(int  rw , int  nr , struct buffer_head *  bhs[] );

rw
    whether to READ or WRITE or maybe READA (readahead)

nr
    number of struct buffer_heads in the array

bhs[]
    array of pointers to struct buffer_head

ll_rw_block takes an array of pointers to struct buffer_heads, and requests an I/O operation on them, either a READ or a WRITE. The third READA option is described in the documentation for generic_make_request which ll_rw_block calls.

This function drops any buffer that it cannot get a lock on (with the BH_Lock state bit), any buffer that appears to be clean when doing a write request, and any buffer that appears to be up-to-date when doing read request. Further it marks as clean buffers that are processed for writing (the buffer cache wonAqt assume that they are actually clean until the buffer gets unlocked).

ll_rw_block sets b_end_io to simple completion handler that marks the buffer up-to-date (if approriate), unlocks the buffer and wakes any waiters.

All of the buffers must be for the same device, and must also be a multiple of the current approved size for the device.