blk_end_request_callback — Special helper function for tricky drivers
int blk_end_request_callback
(struct request * rq, int error, unsigned int nr_bytes, int ()(struct request *) drv_callback);
the request being processed
0 for success, < 0 for error
number of bytes to complete
function called between completion of bios in the request and completion of the request. If the callback returns non 0, this helper returns without completion of the request.
Ends I/O on a number of bytes attached to rq. If rq has leftover, sets it up for the next range of segments.
This special helper function is used only for existing tricky drivers. (e.g. cdrom_newpc_intr of ide-cd) This interface will be removed when such drivers are rewritten. Don't use this interface in other places anymore.
0 - we are done with this request 1 - this request is not freed yet. this request still has pending buffers or the driver doesn't want to finish this request yet.