mirror of
https://mirrors.bfsu.edu.cn/git/linux.git
synced 2024-12-15 15:04:27 +08:00
3664ff82da
Eliminate duplicate boilerplate code for simple modules that contain a single DM target driver without any additional setup code. Add a new module_dm() macro, which replaces the module_init() and module_exit() with template functions that call dm_register_target() and dm_unregister_target() respectively. Signed-off-by: Yangtao Li <frank.li@vivo.com> Signed-off-by: Mike Snitzer <snitzer@kernel.org>
83 lines
1.7 KiB
C
83 lines
1.7 KiB
C
// 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");
|