BLK_RQ_MAP_USER(9) Block Devices BLK_RQ_MAP_USER(9)
NAME blk_rq_map_user - map user data to a request, for REQ_TYPE_BLOCK_PC usage
SYNOPSIS int blk_rq_map_user(struct request_queue * q, struct request * rq, struct rq_map_data * map_data, void __user * ubuf, unsigned long len, gfp_t gfp_mask);
ARGUMENTS q request queue where request should be inserted
rq request structure to fill
map_data pointer to the rq_map_data holding pages (if necessary)
ubuf the user buffer
len length of user data
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 2011 BLK_RQ_MAP_USER(9)