BLK_RQ_MAP_USER_IOV(9) Block Devices BLK_RQ_MAP_USER_IOV(9)
NAME
blk_rq_map_user_iov - map user data to a request, for REQ_TYPE_BLOCK_PC usage
SYNOPSIS
int blk_rq_map_user_iov(struct request_queue * q, struct request * rq, struct rq_map_data * map_data, struct sg_iovec * iov, int iov_count,
unsigned int len, gfp_t gfp_mask);
ARGUMENTS
q
request queue where request should be inserted
rq
request to map data to
map_data
pointer to the rq_map_data holding pages (if necessary)
iov
pointer to the iovec
iov_count
number of elements in the iovec
len
I/O byte count
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. July 2010 BLK_RQ_MAP_USER_IOV(9)
