[linux-2.6-block.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 "dm.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)
{
	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
	12	#include "dm.h"
	13	#include "dm-path-selector.h"
	14
	15	#include <linux/slab.h>
	16
72d94861 AK	17	#define DM_MSG_PREFIX "multipath round-robin"
72d94861 AK	18
1da177e4 LT	19	/*-----------------------------------------------------------------
	20	* Path-handling code, paths are held in lists
	21	---------------------------------------------------------------/
	22	struct path_info {
	23	struct list_head list;
c922d5f7	24	struct dm_path *path;
1da177e4 LT	25	unsigned repeat_count;
	26	};
	27
	28	static void free_paths(struct list_head *paths)
	29	{
	30	struct path_info pi, next;
	31
	32	list_for_each_entry_safe(pi, next, paths, list) {
	33	list_del(&pi->list);
	34	kfree(pi);
	35	}
	36	}
	37
	38	/*-----------------------------------------------------------------
	39	* Round-robin selector
	40	---------------------------------------------------------------/
	41
	42	#define RR_MIN_IO 1000
	43
	44	struct selector {
	45	struct list_head valid_paths;
	46	struct list_head invalid_paths;
	47	};
	48
	49	static struct selector *alloc_selector(void)
	50	{
	51	struct selector s = kmalloc(sizeof(s), GFP_KERNEL);
	52
	53	if (s) {
	54	INIT_LIST_HEAD(&s->valid_paths);
	55	INIT_LIST_HEAD(&s->invalid_paths);
	56	}
	57
	58	return s;
	59	}
	60
	61	static int rr_create(struct path_selector ps, unsigned argc, char *argv)
	62	{
	63	struct selector *s;
	64
	65	s = alloc_selector();
	66	if (!s)
	67	return -ENOMEM;
	68
	69	ps->context = s;
	70	return 0;
	71	}
	72
	73	static void rr_destroy(struct path_selector *ps)
	74	{
	75	struct selector s = (struct selector ) ps->context;
	76
	77	free_paths(&s->valid_paths);
	78	free_paths(&s->invalid_paths);
	79	kfree(s);
	80	ps->context = NULL;
	81	}
	82
c922d5f7	83	static int rr_status(struct path_selector ps, struct dm_path path,
1da177e4 LT	84	status_type_t type, char *result, unsigned int maxlen)
	85	{
	86	struct path_info *pi;
	87	int sz = 0;
	88
	89	if (!path)
	90	DMEMIT("0 ");
	91	else {
	92	switch(type) {
	93	case STATUSTYPE_INFO:
	94	break;
	95	case STATUSTYPE_TABLE:
	96	pi = path->pscontext;
	97	DMEMIT("%u ", pi->repeat_count);
	98	break;
	99	}
	100	}
	101
	102	return sz;
	103	}
	104
	105	/*
	106	* Called during initialisation to register each path with an
	107	* optional repeat_count.
	108	*/
c922d5f7	109	static int rr_add_path(struct path_selector ps, struct dm_path path,
1da177e4 LT	110	int argc, char argv, char error)
	111	{
	112	struct selector s = (struct selector ) ps->context;
	113	struct path_info *pi;
	114	unsigned repeat_count = RR_MIN_IO;
	115
	116	if (argc > 1) {
	117	*error = "round-robin ps: incorrect number of arguments";
	118	return -EINVAL;
	119	}
	120
	121	/* First path argument is number of I/Os before switching path */
	122	if ((argc == 1) && (sscanf(argv[0], "%u", &repeat_count) != 1)) {
	123	*error = "round-robin ps: invalid repeat count";
	124	return -EINVAL;
	125	}
	126
	127	/* allocate the path */
	128	pi = kmalloc(sizeof(*pi), GFP_KERNEL);
	129	if (!pi) {
	130	*error = "round-robin ps: Error allocating path context";
	131	return -ENOMEM;
	132	}
	133
	134	pi->path = path;
	135	pi->repeat_count = repeat_count;
	136
	137	path->pscontext = pi;
	138
5d55fdf9	139	list_add_tail(&pi->list, &s->valid_paths);
1da177e4 LT	140
	141	return 0;
	142	}
	143
c922d5f7	144	static void rr_fail_path(struct path_selector ps, struct dm_path p)
1da177e4 LT	145	{
	146	struct selector s = (struct selector ) ps->context;
	147	struct path_info *pi = p->pscontext;
	148
	149	list_move(&pi->list, &s->invalid_paths);
	150	}
	151
c922d5f7	152	static int rr_reinstate_path(struct path_selector ps, struct dm_path p)
1da177e4 LT	153	{
	154	struct selector s = (struct selector ) ps->context;
	155	struct path_info *pi = p->pscontext;
	156
	157	list_move(&pi->list, &s->valid_paths);
	158
	159	return 0;
	160	}
	161
c922d5f7	162	static struct dm_path rr_select_path(struct path_selector ps,
1da177e4 LT	163	unsigned *repeat_count)
	164	{
	165	struct selector s = (struct selector ) ps->context;
	166	struct path_info *pi = NULL;
	167
	168	if (!list_empty(&s->valid_paths)) {
	169	pi = list_entry(s->valid_paths.next, struct path_info, list);
	170	list_move_tail(&pi->list, &s->valid_paths);
	171	*repeat_count = pi->repeat_count;
	172	}
	173
	174	return pi ? pi->path : NULL;
	175	}
	176
	177	static struct path_selector_type rr_ps = {
	178	.name = "round-robin",
	179	.module = THIS_MODULE,
	180	.table_args = 1,
	181	.info_args = 0,
	182	.create = rr_create,
	183	.destroy = rr_destroy,
	184	.status = rr_status,
	185	.add_path = rr_add_path,
	186	.fail_path = rr_fail_path,
	187	.reinstate_path = rr_reinstate_path,
	188	.select_path = rr_select_path,
	189	};
	190
	191	static int __init dm_rr_init(void)
	192	{
	193	int r = dm_register_path_selector(&rr_ps);
	194
	195	if (r < 0)
72d94861	196	DMERR("register failed %d", r);
1da177e4	197
72d94861	198	DMINFO("version 1.0.0 loaded");
1da177e4 LT	199
	200	return r;
	201	}
	202
	203	static void __exit dm_rr_exit(void)
	204	{
	205	int r = dm_unregister_path_selector(&rr_ps);
	206
	207	if (r < 0)
0cd33124	208	DMERR("unregister failed %d", r);
1da177e4 LT	209	}
	210
	211	module_init(dm_rr_init);
	212	module_exit(dm_rr_exit);
	213
	214	MODULE_DESCRIPTION(DM_NAME " round-robin multipath path selector");
	215	MODULE_AUTHOR("Sistina Software <dm-devel@redhat.com>");
	216	MODULE_LICENSE("GPL");