mirror of
https://mirrors.bfsu.edu.cn/git/linux.git
synced 2024-11-15 16:24:13 +08:00
1eff9d322a
Since commit 63a4cc2486, bio->bi_rw contains flags in the lower
portion and the op code in the higher portions. This means that
old code that relies on manually setting bi_rw is most likely
going to be broken. Instead of letting that brokeness linger,
rename the member, to force old and out-of-tree code to break
at compile time instead of at runtime.
No intended functional changes in this commit.
Signed-off-by: Jens Axboe <axboe@fb.com>
88 lines
1.5 KiB
C
88 lines
1.5 KiB
C
/*
|
|
* Copyright (C) 2003 Jana Saout <jana@saout.de>
|
|
*
|
|
* This file is released under the GPL.
|
|
*/
|
|
|
|
#include <linux/device-mapper.h>
|
|
|
|
#include <linux/module.h>
|
|
#include <linux/init.h>
|
|
#include <linux/bio.h>
|
|
|
|
#define DM_MSG_PREFIX "zero"
|
|
|
|
/*
|
|
* Construct a dummy mapping that only returns zeros
|
|
*/
|
|
static int zero_ctr(struct dm_target *ti, unsigned int argc, char **argv)
|
|
{
|
|
if (argc != 0) {
|
|
ti->error = "No arguments required";
|
|
return -EINVAL;
|
|
}
|
|
|
|
/*
|
|
* Silently drop discards, avoiding -EOPNOTSUPP.
|
|
*/
|
|
ti->num_discard_bios = 1;
|
|
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* Return zeros only on reads
|
|
*/
|
|
static int zero_map(struct dm_target *ti, struct bio *bio)
|
|
{
|
|
switch (bio_op(bio)) {
|
|
case REQ_OP_READ:
|
|
if (bio->bi_opf & REQ_RAHEAD) {
|
|
/* readahead of null bytes only wastes buffer cache */
|
|
return -EIO;
|
|
}
|
|
zero_fill_bio(bio);
|
|
break;
|
|
case REQ_OP_WRITE:
|
|
/* writes get silently dropped */
|
|
break;
|
|
default:
|
|
return -EIO;
|
|
}
|
|
|
|
bio_endio(bio);
|
|
|
|
/* accepted bio, don't make new request */
|
|
return DM_MAPIO_SUBMITTED;
|
|
}
|
|
|
|
static struct target_type zero_target = {
|
|
.name = "zero",
|
|
.version = {1, 1, 0},
|
|
.module = THIS_MODULE,
|
|
.ctr = zero_ctr,
|
|
.map = zero_map,
|
|
};
|
|
|
|
static int __init dm_zero_init(void)
|
|
{
|
|
int r = dm_register_target(&zero_target);
|
|
|
|
if (r < 0)
|
|
DMERR("register failed %d", r);
|
|
|
|
return r;
|
|
}
|
|
|
|
static void __exit dm_zero_exit(void)
|
|
{
|
|
dm_unregister_target(&zero_target);
|
|
}
|
|
|
|
module_init(dm_zero_init)
|
|
module_exit(dm_zero_exit)
|
|
|
|
MODULE_AUTHOR("Jana Saout <jana@saout.de>");
|
|
MODULE_DESCRIPTION(DM_NAME " dummy target returning zeros");
|
|
MODULE_LICENSE("GPL");
|