centos man page for blk_add_request_payload

BLK_ADD_REQUEST_PAYL(9) 					   Block Devices					   BLK_ADD_REQUEST_PAYL(9)

NAME
       blk_add_request_payload - add a payload to a request

SYNOPSIS
       void blk_add_request_payload(struct request * rq, struct page * page, unsigned int len);

ARGUMENTS
       rq
	   request to update

       page
	   page backing the payload

       len
	   length of the payload.

DESCRIPTION
       This allows to later add a payload to an already submitted request by a block driver. The driver needs to take care of freeing the payload
       itself.

       Note that this is a quite horrible hack and nothing but handling of discard requests should ever use it.

COPYRIGHT
Kernel Hackers Manual 3.10					     June 2014						   BLK_ADD_REQUEST_PAYL(9)