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.
COPYRIGHTKernel Hackers Manual 2.6. November 2013 BLK_RQ_MAP_USER(9)