suse man page for blk_rq_map_user_iov

BLK_RQ_MAP_USER_IOV(9)						   Block Devices					    BLK_RQ_MAP_USER_IOV(9)

NAME
       blk_rq_map_user_iov - map user data to a request, for REQ_TYPE_BLOCK_PC usage

SYNOPSIS
       int blk_rq_map_user_iov(struct request_queue * q, struct request * rq, struct rq_map_data * map_data, struct sg_iovec * iov, int iov_count,
			       unsigned int len, gfp_t gfp_mask);

ARGUMENTS
       q
	   request queue where request should be inserted

       rq
	   request to map data to

       map_data
	   pointer to the rq_map_data holding pages (if necessary)

       iov
	   pointer to the iovec

       iov_count
	   number of elements in the iovec

       len
	   I/O byte count

       gfp_mask
	   memory allocation flags

DESCRIPTION
       Data will be mapped directly for zero copy I/O, if possible. Otherwise a kernel bounce buffer is used.

       A matching blk_rq_unmap_user must be issued at the end of I/O, while still in process context.

NOTE
       The mapped bio may need to be bounced through blk_queue_bounce before being submitted to the device, as pages mapped may be out of reach.
       It's the callers responsibility to make sure this happens. The original bio must be passed back in to blk_rq_unmap_user for proper
       unmapping.

COPYRIGHT
Kernel Hackers Manual 2.6.					     July 2010						    BLK_RQ_MAP_USER_IOV(9)