blk_rq_map_user_iov man page on Scientific

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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.	 November 2013		BLK_RQ_MAP_USER_IOV(9)
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