[linux.git] / drivers / md / dm-zero.c

/*
 * Copyright (C) 2003 Christophe Saout <[email protected]>
 *
 * This file is released under the GPL.
 */

#include "dm.h"

#include <linux/module.h>
#include <linux/init.h>
#include <linux/bio.h>

/*
 * 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 = "dm-zero: No arguments required";
		return -EINVAL;
	}

	return 0;
}

/*
 * Return zeros only on reads
 */
static int zero_map(struct dm_target *ti, struct bio *bio,
		      union map_info *map_context)
{
	switch(bio_rw(bio)) {
	case READ:
		zero_fill_bio(bio);
		break;
	case READA:
		/* readahead of null bytes only wastes buffer cache */
		return -EIO;
	case WRITE:
		/* writes get silently dropped */
		break;
	}

	bio_endio(bio, bio->bi_size, 0);

	/* accepted bio, don't make new request */
	return 0;
}

static struct target_type zero_target = {
	.name   = "zero",
	.version = {1, 0, 0},
	.module = THIS_MODULE,
	.ctr    = zero_ctr,
	.map    = zero_map,
};

int __init dm_zero_init(void)
{
	int r = dm_register_target(&zero_target);

	if (r < 0)
		DMERR("zero: register failed %d", r);

	return r;
}

void __exit dm_zero_exit(void)
{
	int r = dm_unregister_target(&zero_target);

	if (r < 0)
		DMERR("zero: unregister failed %d", r);
}

module_init(dm_zero_init)
module_exit(dm_zero_exit)

MODULE_AUTHOR("Christophe Saout <[email protected]>");
MODULE_DESCRIPTION(DM_NAME " dummy target returning zeros");
MODULE_LICENSE("GPL");
Commit	Line	Data
1da177e4 LT	1	/*
	2	* Copyright (C) 2003 Christophe Saout <[email protected]>
	3	*
	4	* This file is released under the GPL.
	5	*/
	6
	7	#include "dm.h"
	8
	9	#include <linux/module.h>
	10	#include <linux/init.h>
	11	#include <linux/bio.h>
	12
	13	/*
	14	* Construct a dummy mapping that only returns zeros
	15	*/
	16	static int zero_ctr(struct dm_target ti, unsigned int argc, char *argv)
	17	{
	18	if (argc != 0) {
	19	ti->error = "dm-zero: No arguments required";
	20	return -EINVAL;
	21	}
	22
	23	return 0;
	24	}
	25
	26	/*
	27	* Return zeros only on reads
	28	*/
	29	static int zero_map(struct dm_target ti, struct bio bio,
	30	union map_info *map_context)
	31	{
	32	switch(bio_rw(bio)) {
	33	case READ:
	34	zero_fill_bio(bio);
	35	break;
	36	case READA:
	37	/* readahead of null bytes only wastes buffer cache */
	38	return -EIO;
	39	case WRITE:
	40	/* writes get silently dropped */
	41	break;
	42	}
	43
	44	bio_endio(bio, bio->bi_size, 0);
	45
	46	/* accepted bio, don't make new request */
	47	return 0;
	48	}
	49
	50	static struct target_type zero_target = {
	51	.name = "zero",
	52	.version = {1, 0, 0},
	53	.module = THIS_MODULE,
	54	.ctr = zero_ctr,
	55	.map = zero_map,
	56	};
	57
	58	int __init dm_zero_init(void)
	59	{
	60	int r = dm_register_target(&zero_target);
	61
	62	if (r < 0)
	63	DMERR("zero: register failed %d", r);
	64
65	return r;
66	}
67
68	void __exit dm_zero_exit(void)
69	{
70	int r = dm_unregister_target(&zero_target);
71
72	if (r < 0)
73	DMERR("zero: unregister failed %d", r);
74	}
75
76	module_init(dm_zero_init)
77	module_exit(dm_zero_exit)
78
79	MODULE_AUTHOR("Christophe Saout <[email protected]>");
80	MODULE_DESCRIPTION(DM_NAME " dummy target returning zeros");
81	MODULE_LICENSE("GPL");