Contributors: 11
| Author |
Tokens |
Token Proportion |
Commits |
Commit Proportion |
| Alasdair G. Kergon |
156 |
63.41% |
3 |
20.00% |
| Mikulas Patocka |
44 |
17.89% |
2 |
13.33% |
| Christoph Hellwig |
18 |
7.32% |
2 |
13.33% |
| Kevin Corry |
10 |
4.07% |
1 |
6.67% |
| Mike Snitzer |
6 |
2.44% |
1 |
6.67% |
| Jeffle Xu |
5 |
2.03% |
1 |
6.67% |
| Jana Saout |
2 |
0.81% |
1 |
6.67% |
| Yangtao Li |
2 |
0.81% |
1 |
6.67% |
| Jens Axboe |
1 |
0.41% |
1 |
6.67% |
| Heinz Mauelshagen |
1 |
0.41% |
1 |
6.67% |
| Kiyoshi Ueda |
1 |
0.41% |
1 |
6.67% |
| Total |
246 |
|
15 |
|
// SPDX-License-Identifier: GPL-2.0-only
/*
* 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;
ti->discards_supported = true;
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 DM_MAPIO_KILL;
}
zero_fill_bio(bio);
break;
case REQ_OP_WRITE:
case REQ_OP_DISCARD:
/* writes get silently dropped */
break;
default:
return DM_MAPIO_KILL;
}
bio_endio(bio);
/* accepted bio, don't make new request */
return DM_MAPIO_SUBMITTED;
}
static void zero_io_hints(struct dm_target *ti, struct queue_limits *limits)
{
limits->max_discard_sectors = UINT_MAX;
limits->max_hw_discard_sectors = UINT_MAX;
limits->discard_granularity = 512;
}
static struct target_type zero_target = {
.name = "zero",
.version = {1, 2, 0},
.features = DM_TARGET_NOWAIT,
.module = THIS_MODULE,
.ctr = zero_ctr,
.map = zero_map,
.io_hints = zero_io_hints,
};
module_dm(zero);
MODULE_AUTHOR("Jana Saout <jana@saout.de>");
MODULE_DESCRIPTION(DM_NAME " dummy target returning zeros");
MODULE_LICENSE("GPL");