blk_rq_map_user

blk_rq_map_user_iov
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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.