[net-next-2.6.git] / drivers / md / dm-round-robin.c

/*
 * Copyright (C) 2003 Sistina Software.
 * Copyright (C) 2004-2005 Red Hat, Inc. All rights reserved.
 *
 * Module Author: Heinz Mauelshagen
 *
 * This file is released under the GPL.
 *
 * Round-robin path selector.
 */

#include <linux/device-mapper.h>

#include "dm-path-selector.h"

#include <linux/slab.h>

#define DM_MSG_PREFIX "multipath round-robin"

/*-----------------------------------------------------------------
 * Path-handling code, paths are held in lists
 *---------------------------------------------------------------*/
struct path_info {
	struct list_head list;
	struct dm_path *path;
	unsigned repeat_count;
};

static void free_paths(struct list_head *paths)
{
	struct path_info *pi, *next;

	list_for_each_entry_safe(pi, next, paths, list) {
		list_del(&pi->list);
		kfree(pi);
	}
}

/*-----------------------------------------------------------------
 * Round-robin selector
 *---------------------------------------------------------------*/

#define RR_MIN_IO		1000

struct selector {
	struct list_head valid_paths;
	struct list_head invalid_paths;
};

static struct selector *alloc_selector(void)
{
	struct selector *s = kmalloc(sizeof(*s), GFP_KERNEL);

	if (s) {
		INIT_LIST_HEAD(&s->valid_paths);
		INIT_LIST_HEAD(&s->invalid_paths);
	}

	return s;
}

static int rr_create(struct path_selector *ps, unsigned argc, char **argv)
{
	struct selector *s;

	s = alloc_selector();
	if (!s)
		return -ENOMEM;

	ps->context = s;
	return 0;
}

static void rr_destroy(struct path_selector *ps)
{
	struct selector *s = (struct selector *) ps->context;

	free_paths(&s->valid_paths);
	free_paths(&s->invalid_paths);
	kfree(s);
	ps->context = NULL;
}

static int rr_status(struct path_selector *ps, struct dm_path *path,
		     status_type_t type, char *result, unsigned int maxlen)
{
	struct path_info *pi;
	int sz = 0;

	if (!path)
		DMEMIT("0 ");
	else {
		switch(type) {
		case STATUSTYPE_INFO:
			break;
		case STATUSTYPE_TABLE:
			pi = path->pscontext;
			DMEMIT("%u ", pi->repeat_count);
			break;
		}
	}

	return sz;
}

/*
 * Called during initialisation to register each path with an
 * optional repeat_count.
 */
static int rr_add_path(struct path_selector *ps, struct dm_path *path,
		       int argc, char **argv, char **error)
{
	struct selector *s = (struct selector *) ps->context;
	struct path_info *pi;
	unsigned repeat_count = RR_MIN_IO;

	if (argc > 1) {
		*error = "round-robin ps: incorrect number of arguments";
		return -EINVAL;
	}

	/* First path argument is number of I/Os before switching path */
	if ((argc == 1) && (sscanf(argv[0], "%u", &repeat_count) != 1)) {
		*error = "round-robin ps: invalid repeat count";
		return -EINVAL;
	}

	/* allocate the path */
	pi = kmalloc(sizeof(*pi), GFP_KERNEL);
	if (!pi) {
		*error = "round-robin ps: Error allocating path context";
		return -ENOMEM;
	}

	pi->path = path;
	pi->repeat_count = repeat_count;

	path->pscontext = pi;

	list_add_tail(&pi->list, &s->valid_paths);

	return 0;
}

static void rr_fail_path(struct path_selector *ps, struct dm_path *p)
{
	struct selector *s = (struct selector *) ps->context;
	struct path_info *pi = p->pscontext;

	list_move(&pi->list, &s->invalid_paths);
}

static int rr_reinstate_path(struct path_selector *ps, struct dm_path *p)
{
	struct selector *s = (struct selector *) ps->context;
	struct path_info *pi = p->pscontext;

	list_move(&pi->list, &s->valid_paths);

	return 0;
}

static struct dm_path *rr_select_path(struct path_selector *ps,
				      unsigned *repeat_count, size_t nr_bytes)
{
	struct selector *s = (struct selector *) ps->context;
	struct path_info *pi = NULL;

	if (!list_empty(&s->valid_paths)) {
		pi = list_entry(s->valid_paths.next, struct path_info, list);
		list_move_tail(&pi->list, &s->valid_paths);
		*repeat_count = pi->repeat_count;
	}

	return pi ? pi->path : NULL;
}

static struct path_selector_type rr_ps = {
	.name = "round-robin",
	.module = THIS_MODULE,
	.table_args = 1,
	.info_args = 0,
	.create = rr_create,
	.destroy = rr_destroy,
	.status = rr_status,
	.add_path = rr_add_path,
	.fail_path = rr_fail_path,
	.reinstate_path = rr_reinstate_path,
	.select_path = rr_select_path,
};

static int __init dm_rr_init(void)
{
	int r = dm_register_path_selector(&rr_ps);

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

	DMINFO("version 1.0.0 loaded");

	return r;
}

static void __exit dm_rr_exit(void)
{
	int r = dm_unregister_path_selector(&rr_ps);

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

module_init(dm_rr_init);
module_exit(dm_rr_exit);

MODULE_DESCRIPTION(DM_NAME " round-robin multipath path selector");
MODULE_AUTHOR("Sistina Software <dm-devel@redhat.com>");
MODULE_LICENSE("GPL");
Commit	Line	Data
1da177e4 LT	1	/*
	2	* Copyright (C) 2003 Sistina Software.
	3	* Copyright (C) 2004-2005 Red Hat, Inc. All rights reserved.
	4	*
	5	* Module Author: Heinz Mauelshagen
	6	*
	7	* This file is released under the GPL.
	8	*
	9	* Round-robin path selector.
	10	*/
	11
586e80e6 MP	12	#include <linux/device-mapper.h>
586e80e6 MP	13
1da177e4 LT	14	#include "dm-path-selector.h"
	15
	16	#include <linux/slab.h>
	17
72d94861 AK	18	#define DM_MSG_PREFIX "multipath round-robin"
72d94861 AK	19
1da177e4 LT	20	/*-----------------------------------------------------------------
	21	* Path-handling code, paths are held in lists
	22	---------------------------------------------------------------/
	23	struct path_info {
	24	struct list_head list;
c922d5f7	25	struct dm_path *path;
1da177e4 LT	26	unsigned repeat_count;
	27	};
	28
	29	static void free_paths(struct list_head *paths)
	30	{
	31	struct path_info pi, next;
	32
	33	list_for_each_entry_safe(pi, next, paths, list) {
	34	list_del(&pi->list);
	35	kfree(pi);
	36	}
	37	}
	38
	39	/*-----------------------------------------------------------------
	40	* Round-robin selector
	41	---------------------------------------------------------------/
	42
	43	#define RR_MIN_IO 1000
	44
	45	struct selector {
	46	struct list_head valid_paths;
	47	struct list_head invalid_paths;
	48	};
	49
	50	static struct selector *alloc_selector(void)
	51	{
	52	struct selector s = kmalloc(sizeof(s), GFP_KERNEL);
	53
	54	if (s) {
	55	INIT_LIST_HEAD(&s->valid_paths);
	56	INIT_LIST_HEAD(&s->invalid_paths);
	57	}
	58
	59	return s;
	60	}
	61
	62	static int rr_create(struct path_selector ps, unsigned argc, char *argv)
	63	{
	64	struct selector *s;
	65
	66	s = alloc_selector();
	67	if (!s)
	68	return -ENOMEM;
	69
	70	ps->context = s;
	71	return 0;
	72	}
	73
	74	static void rr_destroy(struct path_selector *ps)
	75	{
	76	struct selector s = (struct selector ) ps->context;
	77
	78	free_paths(&s->valid_paths);
	79	free_paths(&s->invalid_paths);
	80	kfree(s);
	81	ps->context = NULL;
	82	}
	83
c922d5f7	84	static int rr_status(struct path_selector ps, struct dm_path path,
1da177e4 LT	85	status_type_t type, char *result, unsigned int maxlen)
	86	{
	87	struct path_info *pi;
	88	int sz = 0;
	89
	90	if (!path)
	91	DMEMIT("0 ");
	92	else {
	93	switch(type) {
	94	case STATUSTYPE_INFO:
	95	break;
	96	case STATUSTYPE_TABLE:
	97	pi = path->pscontext;
	98	DMEMIT("%u ", pi->repeat_count);
	99	break;
	100	}
	101	}
	102
	103	return sz;
	104	}
	105
	106	/*
	107	* Called during initialisation to register each path with an
	108	* optional repeat_count.
	109	*/
c922d5f7	110	static int rr_add_path(struct path_selector ps, struct dm_path path,
1da177e4 LT	111	int argc, char argv, char error)
	112	{
	113	struct selector s = (struct selector ) ps->context;
	114	struct path_info *pi;
	115	unsigned repeat_count = RR_MIN_IO;
	116
	117	if (argc > 1) {
	118	*error = "round-robin ps: incorrect number of arguments";
	119	return -EINVAL;
	120	}
	121
	122	/* First path argument is number of I/Os before switching path */
	123	if ((argc == 1) && (sscanf(argv[0], "%u", &repeat_count) != 1)) {
	124	*error = "round-robin ps: invalid repeat count";
	125	return -EINVAL;
	126	}
	127
	128	/* allocate the path */
	129	pi = kmalloc(sizeof(*pi), GFP_KERNEL);
	130	if (!pi) {
	131	*error = "round-robin ps: Error allocating path context";
	132	return -ENOMEM;
	133	}
	134
	135	pi->path = path;
	136	pi->repeat_count = repeat_count;
	137
	138	path->pscontext = pi;
	139
5d55fdf9	140	list_add_tail(&pi->list, &s->valid_paths);
1da177e4 LT	141
	142	return 0;
	143	}
	144
c922d5f7	145	static void rr_fail_path(struct path_selector ps, struct dm_path p)
1da177e4 LT	146	{
	147	struct selector s = (struct selector ) ps->context;
	148	struct path_info *pi = p->pscontext;
	149
	150	list_move(&pi->list, &s->invalid_paths);
	151	}
	152
c922d5f7	153	static int rr_reinstate_path(struct path_selector ps, struct dm_path p)
1da177e4 LT	154	{
	155	struct selector s = (struct selector ) ps->context;
	156	struct path_info *pi = p->pscontext;
	157
	158	list_move(&pi->list, &s->valid_paths);
	159
	160	return 0;
	161	}
	162
c922d5f7	163	static struct dm_path rr_select_path(struct path_selector ps,
02ab823f	164	unsigned *repeat_count, size_t nr_bytes)
1da177e4 LT	165	{
	166	struct selector s = (struct selector ) ps->context;
	167	struct path_info *pi = NULL;
	168
	169	if (!list_empty(&s->valid_paths)) {
	170	pi = list_entry(s->valid_paths.next, struct path_info, list);
	171	list_move_tail(&pi->list, &s->valid_paths);
	172	*repeat_count = pi->repeat_count;
	173	}
	174
	175	return pi ? pi->path : NULL;
	176	}
	177
	178	static struct path_selector_type rr_ps = {
	179	.name = "round-robin",
	180	.module = THIS_MODULE,
	181	.table_args = 1,
	182	.info_args = 0,
	183	.create = rr_create,
	184	.destroy = rr_destroy,
	185	.status = rr_status,
	186	.add_path = rr_add_path,
	187	.fail_path = rr_fail_path,
	188	.reinstate_path = rr_reinstate_path,
	189	.select_path = rr_select_path,
	190	};
	191
	192	static int __init dm_rr_init(void)
	193	{
	194	int r = dm_register_path_selector(&rr_ps);
	195
	196	if (r < 0)
72d94861	197	DMERR("register failed %d", r);
1da177e4	198
72d94861	199	DMINFO("version 1.0.0 loaded");
1da177e4 LT	200
	201	return r;
	202	}
	203
	204	static void __exit dm_rr_exit(void)
	205	{
	206	int r = dm_unregister_path_selector(&rr_ps);
	207
	208	if (r < 0)
0cd33124	209	DMERR("unregister failed %d", r);
1da177e4 LT	210	}
	211
	212	module_init(dm_rr_init);
	213	module_exit(dm_rr_exit);
	214
	215	MODULE_DESCRIPTION(DM_NAME " round-robin multipath path selector");
	216	MODULE_AUTHOR("Sistina Software <dm-devel@redhat.com>");
	217	MODULE_LICENSE("GPL");