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
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);
request queue where request should be inserted
request to map data to
pointer to the rq_map_data holding pages (if necessary)
pointer to the iovec
number of elements in the iovec
I/O byte count
memory allocation flags
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.
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.
COPYRIGHTKernel Hackers Manual 3.8. June 2014 BLK_RQ_MAP_USER_IOV(9)