Linux Certif

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blk_rq_map_user

NAME

blk_rq_map_user - map user data to a request, for REQ_BLOCK_PC usage

SYNOPSIS

int blk_rq_map_user(struct request_queue * q, struct request * rq, void __user * ubuf, unsigned long len);

ARGUMENTS

q

request queue where request should be inserted

rq

request structure to fill

ubuf

the user buffer

len

length of user data

DESCRIPTION

Data will be mapped directly for zero copy io, if possible. Otherwise a kernel bounce buffer is used.

A matching blk_rq_unmap_user must be issued at the end of io, 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.

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