blk_rq_map_user - map user data to a request, for REQ_TYPE_BLOCK_PC usage
2. 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 );
3. ARGUMENTS ▲
request queue where request should be inserted
request structure to fill
pointer to the rq_map_data holding pages (if necessary)
the user buffer
length of user data
memory allocation flags
4. 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.
5. 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. ItAqs the callers responsibility to make sure this happens. The original bio must be passed back in to blk_rq_unmap_user for proper unmapping.
6. COPYRIGHT ▲