BLK_RQ_MAP_USER_IOV

NAME

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