Map kernel data to a request, for req_type_block_pc usage
int blk_rq_map_kern(struct request_queue * q, struct request * rq, void * kbuf, unsigned int len, gfp_t gfp_mask);
q
request queue where request should be inserted
rq
request to fill
kbuf
the kernel buffer
len
length of user data
gfp_mask
memory allocation flags
Data will be mapped directly if possible. Otherwise a bounce buffer is used. Can be called multiple times to append multiple buffers.