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, const struct iov_iter * iter,
                               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)

       iter
           iovec iterator

       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 4.8.                 January 2017                    BLK_RQ_MAP_USER_IOV(9)