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 3.8. June 2014 BLK_RQ_MAP_USER(9)
