1BLK_RQ_MAP_USER(9)               Block Devices              BLK_RQ_MAP_USER(9)
2
3
4

NAME

6       blk_rq_map_user - map user data to a request, for REQ_TYPE_BLOCK_PC
7       usage
8

SYNOPSIS

10       int blk_rq_map_user(struct request_queue * q, struct request * rq,
11                           struct rq_map_data * map_data, void __user * ubuf,
12                           unsigned long len, gfp_t gfp_mask);
13

ARGUMENTS

15       q
16           request queue where request should be inserted
17
18       rq
19           request structure to fill
20
21       map_data
22           pointer to the rq_map_data holding pages (if necessary)
23
24       ubuf
25           the user buffer
26
27       len
28           length of user data
29
30       gfp_mask
31           memory allocation flags
32

DESCRIPTION

34       Data will be mapped directly for zero copy I/O, if possible. Otherwise
35       a kernel bounce buffer is used.
36
37       A matching blk_rq_unmap_user must be issued at the end of I/O, while
38       still in process context.
39

NOTE

41       The mapped bio may need to be bounced through blk_queue_bounce before
42       being submitted to the device, as pages mapped may be out of reach.
43       It´s the callers responsibility to make sure this happens. The original
44       bio must be passed back in to blk_rq_unmap_user for proper unmapping.
45

47Kernel Hackers Manual 2.6.         June 2019                BLK_RQ_MAP_USER(9)
Impressum