[linux.git] / lib / list_sort.c

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/list_sort.h>
#include <linux/slab.h>
#include <linux/list.h>

#define MAX_LIST_LENGTH_BITS 20

/*
 * Returns a list organized in an intermediate format suited
 * to chaining of merge() calls: null-terminated, no reserved or
 * sentinel head node, "prev" links not maintained.
 */
static struct list_head *merge(void *priv,
				int (*cmp)(void *priv, struct list_head *a,
					struct list_head *b),
				struct list_head *a, struct list_head *b)
{
	struct list_head head, *tail = &head;

	while (a && b) {
		/* if equal, take 'a' -- important for sort stability */
		if ((*cmp)(priv, a, b) <= 0) {
			tail->next = a;
			a = a->next;
		} else {
			tail->next = b;
			b = b->next;
		}
		tail = tail->next;
	}
	tail->next = a?:b;
	return head.next;
}

/*
 * Combine final list merge with restoration of standard doubly-linked
 * list structure.  This approach duplicates code from merge(), but
 * runs faster than the tidier alternatives of either a separate final
 * prev-link restoration pass, or maintaining the prev links
 * throughout.
 */
static void merge_and_restore_back_links(void *priv,
				int (*cmp)(void *priv, struct list_head *a,
					struct list_head *b),
				struct list_head *head,
				struct list_head *a, struct list_head *b)
{
	struct list_head *tail = head;

	while (a && b) {
		/* if equal, take 'a' -- important for sort stability */
		if ((*cmp)(priv, a, b) <= 0) {
			tail->next = a;
			a->prev = tail;
			a = a->next;
		} else {
			tail->next = b;
			b->prev = tail;
			b = b->next;
		}
		tail = tail->next;
	}
	tail->next = a ? : b;

	do {
		/*
		 * In worst cases this loop may run many iterations.
		 * Continue callbacks to the client even though no
		 * element comparison is needed, so the client's cmp()
		 * routine can invoke cond_resched() periodically.
		 */
		(*cmp)(priv, tail->next, tail->next);

		tail->next->prev = tail;
		tail = tail->next;
	} while (tail->next);

	tail->next = head;
	head->prev = tail;
}

/**
 * list_sort - sort a list
 * @priv: private data, opaque to list_sort(), passed to @cmp
 * @head: the list to sort
 * @cmp: the elements comparison function
 *
 * This function implements "merge sort", which has O(nlog(n))
 * complexity.
 *
 * The comparison function @cmp must return a negative value if @a
 * should sort before @b, and a positive value if @a should sort after
 * @b. If @a and @b are equivalent, and their original relative
 * ordering is to be preserved, @cmp must return 0.
 */
void list_sort(void *priv, struct list_head *head,
		int (*cmp)(void *priv, struct list_head *a,
			struct list_head *b))
{
	struct list_head *part[MAX_LIST_LENGTH_BITS+1]; /* sorted partial lists
						-- last slot is a sentinel */
	int lev;  /* index into part[] */
	int max_lev = 0;
	struct list_head *list;

	if (list_empty(head))
		return;

	memset(part, 0, sizeof(part));

	head->prev->next = NULL;
	list = head->next;

	while (list) {
		struct list_head *cur = list;
		list = list->next;
		cur->next = NULL;

		for (lev = 0; part[lev]; lev++) {
			cur = merge(priv, cmp, part[lev], cur);
			part[lev] = NULL;
		}
		if (lev > max_lev) {
			if (unlikely(lev >= ARRAY_SIZE(part)-1)) {
				printk_once(KERN_DEBUG "list passed to"
					" list_sort() too long for"
					" efficiency\n");
				lev--;
			}
			max_lev = lev;
		}
		part[lev] = cur;
	}

	for (lev = 0; lev < max_lev; lev++)
		if (part[lev])
			list = merge(priv, cmp, part[lev], list);

	merge_and_restore_back_links(priv, cmp, head, part[max_lev], list);
}
EXPORT_SYMBOL(list_sort);

#ifdef CONFIG_TEST_LIST_SORT

#include <linux/random.h>

/*
 * The pattern of set bits in the list length determines which cases
 * are hit in list_sort().
 */
#define TEST_LIST_LEN (512+128+2) /* not including head */

#define TEST_POISON1 0xDEADBEEF
#define TEST_POISON2 0xA324354C

struct debug_el {
	unsigned int poison1;
	struct list_head list;
	unsigned int poison2;
	int value;
	unsigned serial;
};

/* Array, containing pointers to all elements in the test list */
static struct debug_el **elts __initdata;

static int __init check(struct debug_el *ela, struct debug_el *elb)
{
	if (ela->serial >= TEST_LIST_LEN) {
		printk(KERN_ERR "list_sort_test: error: incorrect serial %d\n",
				ela->serial);
		return -EINVAL;
	}
	if (elb->serial >= TEST_LIST_LEN) {
		printk(KERN_ERR "list_sort_test: error: incorrect serial %d\n",
				elb->serial);
		return -EINVAL;
	}
	if (elts[ela->serial] != ela || elts[elb->serial] != elb) {
		printk(KERN_ERR "list_sort_test: error: phantom element\n");
		return -EINVAL;
	}
	if (ela->poison1 != TEST_POISON1 || ela->poison2 != TEST_POISON2) {
		printk(KERN_ERR "list_sort_test: error: bad poison: %#x/%#x\n",
				ela->poison1, ela->poison2);
		return -EINVAL;
	}
	if (elb->poison1 != TEST_POISON1 || elb->poison2 != TEST_POISON2) {
		printk(KERN_ERR "list_sort_test: error: bad poison: %#x/%#x\n",
				elb->poison1, elb->poison2);
		return -EINVAL;
	}
	return 0;
}

static int __init cmp(void *priv, struct list_head *a, struct list_head *b)
{
	struct debug_el *ela, *elb;

	ela = container_of(a, struct debug_el, list);
	elb = container_of(b, struct debug_el, list);

	check(ela, elb);
	return ela->value - elb->value;
}

static int __init list_sort_test(void)
{
	int i, count = 1, err = -EINVAL;
	struct debug_el *el;
	struct list_head *cur, *tmp;
	LIST_HEAD(head);

	printk(KERN_DEBUG "list_sort_test: start testing list_sort()\n");

	elts = kmalloc(sizeof(void *) * TEST_LIST_LEN, GFP_KERNEL);
	if (!elts) {
		printk(KERN_ERR "list_sort_test: error: cannot allocate "
				"memory\n");
		goto exit;
	}

	for (i = 0; i < TEST_LIST_LEN; i++) {
		el = kmalloc(sizeof(*el), GFP_KERNEL);
		if (!el) {
			printk(KERN_ERR "list_sort_test: error: cannot "
					"allocate memory\n");
			goto exit;
		}
		 /* force some equivalencies */
		el->value = prandom_u32() % (TEST_LIST_LEN / 3);
		el->serial = i;
		el->poison1 = TEST_POISON1;
		el->poison2 = TEST_POISON2;
		elts[i] = el;
		list_add_tail(&el->list, &head);
	}

	list_sort(NULL, &head, cmp);

	for (cur = head.next; cur->next != &head; cur = cur->next) {
		struct debug_el *el1;
		int cmp_result;

		if (cur->next->prev != cur) {
			printk(KERN_ERR "list_sort_test: error: list is "
					"corrupted\n");
			goto exit;
		}

		cmp_result = cmp(NULL, cur, cur->next);
		if (cmp_result > 0) {
			printk(KERN_ERR "list_sort_test: error: list is not "
					"sorted\n");
			goto exit;
		}

		el = container_of(cur, struct debug_el, list);
		el1 = container_of(cur->next, struct debug_el, list);
		if (cmp_result == 0 && el->serial >= el1->serial) {
			printk(KERN_ERR "list_sort_test: error: order of "
					"equivalent elements not preserved\n");
			goto exit;
		}

		if (check(el, el1)) {
			printk(KERN_ERR "list_sort_test: error: element check "
					"failed\n");
			goto exit;
		}
		count++;
	}

	if (count != TEST_LIST_LEN) {
		printk(KERN_ERR "list_sort_test: error: bad list length %d",
				count);
		goto exit;
	}

	err = 0;
exit:
	kfree(elts);
	list_for_each_safe(cur, tmp, &head) {
		list_del(cur);
		kfree(container_of(cur, struct debug_el, list));
	}
	return err;
}
module_init(list_sort_test);
#endif /* CONFIG_TEST_LIST_SORT */
Commit	Line	Data
2c761270 DC	1	#include <linux/kernel.h>
	2	#include <linux/module.h>
	3	#include <linux/list_sort.h>
	4	#include <linux/slab.h>
	5	#include <linux/list.h>
	6
835cc0c8 DM	7	#define MAX_LIST_LENGTH_BITS 20
	8
	9	/*
	10	* Returns a list organized in an intermediate format suited
	11	* to chaining of merge() calls: null-terminated, no reserved or
	12	* sentinel head node, "prev" links not maintained.
	13	*/
	14	static struct list_head merge(void priv,
	15	int (cmp)(void priv, struct list_head *a,
	16	struct list_head *b),
	17	struct list_head a, struct list_head b)
	18	{
	19	struct list_head head, *tail = &head;
	20
	21	while (a && b) {
	22	/* if equal, take 'a' -- important for sort stability */
	23	if ((*cmp)(priv, a, b) <= 0) {
	24	tail->next = a;
	25	a = a->next;
	26	} else {
	27	tail->next = b;
	28	b = b->next;
	29	}
	30	tail = tail->next;
	31	}
	32	tail->next = a?:b;
	33	return head.next;
	34	}
	35
	36	/*
	37	* Combine final list merge with restoration of standard doubly-linked
	38	* list structure. This approach duplicates code from merge(), but
	39	* runs faster than the tidier alternatives of either a separate final
	40	* prev-link restoration pass, or maintaining the prev links
	41	* throughout.
	42	*/
	43	static void merge_and_restore_back_links(void *priv,
	44	int (cmp)(void priv, struct list_head *a,
	45	struct list_head *b),
	46	struct list_head *head,
	47	struct list_head a, struct list_head b)
	48	{
	49	struct list_head *tail = head;
	50
	51	while (a && b) {
	52	/* if equal, take 'a' -- important for sort stability */
	53	if ((*cmp)(priv, a, b) <= 0) {
	54	tail->next = a;
	55	a->prev = tail;
	56	a = a->next;
	57	} else {
	58	tail->next = b;
	59	b->prev = tail;
	60	b = b->next;
	61	}
	62	tail = tail->next;
	63	}
	64	tail->next = a ? : b;
	65
	66	do {
	67	/*
	68	* In worst cases this loop may run many iterations.
	69	* Continue callbacks to the client even though no
	70	* element comparison is needed, so the client's cmp()
71	* routine can invoke cond_resched() periodically.
72	*/
f015ac3e	73	(*cmp)(priv, tail->next, tail->next);
835cc0c8 DM	74
	75	tail->next->prev = tail;
	76	tail = tail->next;
	77	} while (tail->next);
	78
	79	tail->next = head;
	80	head->prev = tail;
	81	}
	82
2c761270	83	/**
02b12b7a DM	84	* list_sort - sort a list
02b12b7a DM	85	* @priv: private data, opaque to list_sort(), passed to @cmp
2c761270 DC	86	* @head: the list to sort
	87	* @cmp: the elements comparison function
	88	*
02b12b7a DM	89	* This function implements "merge sort", which has O(nlog(n))
02b12b7a DM	90	* complexity.
2c761270	91	*
02b12b7a DM	92	* The comparison function @cmp must return a negative value if @a
	93	* should sort before @b, and a positive value if @a should sort after
	94	* @b. If @a and @b are equivalent, and their original relative
	95	* ordering is to be preserved, @cmp must return 0.
2c761270 DC	96	*/
2c761270 DC	97	void list_sort(void priv, struct list_head head,
835cc0c8 DM	98	int (cmp)(void priv, struct list_head *a,
835cc0c8 DM	99	struct list_head *b))
2c761270	100	{
835cc0c8 DM	101	struct list_head part[MAX_LIST_LENGTH_BITS+1]; / sorted partial lists
	102	-- last slot is a sentinel */
	103	int lev; /* index into part[] */
	104	int max_lev = 0;
	105	struct list_head *list;
2c761270 DC	106
	107	if (list_empty(head))
	108	return;
	109
835cc0c8 DM	110	memset(part, 0, sizeof(part));
	111
	112	head->prev->next = NULL;
2c761270	113	list = head->next;
2c761270	114
835cc0c8 DM	115	while (list) {
	116	struct list_head *cur = list;
	117	list = list->next;
	118	cur->next = NULL;
	119
	120	for (lev = 0; part[lev]; lev++) {
	121	cur = merge(priv, cmp, part[lev], cur);
	122	part[lev] = NULL;
	123	}
	124	if (lev > max_lev) {
	125	if (unlikely(lev >= ARRAY_SIZE(part)-1)) {
	126	printk_once(KERN_DEBUG "list passed to"
	127	" list_sort() too long for"
	128	" efficiency\n");
	129	lev--;
2c761270	130	}
835cc0c8	131	max_lev = lev;
2c761270	132	}
835cc0c8 DM	133	part[lev] = cur;
835cc0c8 DM	134	}
2c761270	135
835cc0c8 DM	136	for (lev = 0; lev < max_lev; lev++)
	137	if (part[lev])
	138	list = merge(priv, cmp, part[lev], list);
2c761270	139
835cc0c8 DM	140	merge_and_restore_back_links(priv, cmp, head, part[max_lev], list);
	141	}
	142	EXPORT_SYMBOL(list_sort);
2c761270	143
6d411e6c	144	#ifdef CONFIG_TEST_LIST_SORT
eeee9ebb AB	145
	146	#include <linux/random.h>
	147
041b78f2 AB	148	/*
	149	* The pattern of set bits in the list length determines which cases
	150	* are hit in list_sort().
	151	*/
	152	#define TEST_LIST_LEN (512+128+2) /* not including head */
	153
	154	#define TEST_POISON1 0xDEADBEEF
	155	#define TEST_POISON2 0xA324354C
	156
835cc0c8	157	struct debug_el {
041b78f2	158	unsigned int poison1;
eeee9ebb	159	struct list_head list;
041b78f2	160	unsigned int poison2;
835cc0c8 DM	161	int value;
	162	unsigned serial;
	163	};
2c761270	164
041b78f2 AB	165	/* Array, containing pointers to all elements in the test list */
	166	static struct debug_el **elts __initdata;
	167
	168	static int __init check(struct debug_el ela, struct debug_el elb)
835cc0c8	169	{
041b78f2 AB	170	if (ela->serial >= TEST_LIST_LEN) {
	171	printk(KERN_ERR "list_sort_test: error: incorrect serial %d\n",
	172	ela->serial);
	173	return -EINVAL;
	174	}
	175	if (elb->serial >= TEST_LIST_LEN) {
	176	printk(KERN_ERR "list_sort_test: error: incorrect serial %d\n",
	177	elb->serial);
	178	return -EINVAL;
	179	}
	180	if (elts[ela->serial] != ela \|\| elts[elb->serial] != elb) {
	181	printk(KERN_ERR "list_sort_test: error: phantom element\n");
	182	return -EINVAL;
	183	}
	184	if (ela->poison1 != TEST_POISON1 \|\| ela->poison2 != TEST_POISON2) {
	185	printk(KERN_ERR "list_sort_test: error: bad poison: %#x/%#x\n",
	186	ela->poison1, ela->poison2);
	187	return -EINVAL;
	188	}
	189	if (elb->poison1 != TEST_POISON1 \|\| elb->poison2 != TEST_POISON2) {
	190	printk(KERN_ERR "list_sort_test: error: bad poison: %#x/%#x\n",
	191	elb->poison1, elb->poison2);
	192	return -EINVAL;
	193	}
	194	return 0;
2c761270 DC	195	}
2c761270 DC	196
041b78f2 AB	197	static int __init cmp(void priv, struct list_head a, struct list_head *b)
	198	{
	199	struct debug_el ela, elb;
	200
	201	ela = container_of(a, struct debug_el, list);
	202	elb = container_of(b, struct debug_el, list);
	203
	204	check(ela, elb);
	205	return ela->value - elb->value;
	206	}
835cc0c8 DM	207
	208	static int __init list_sort_test(void)
	209	{
f3dc0e38 AB	210	int i, count = 1, err = -EINVAL;
	211	struct debug_el *el;
	212	struct list_head cur, tmp;
	213	LIST_HEAD(head);
835cc0c8	214
014afa94	215	printk(KERN_DEBUG "list_sort_test: start testing list_sort()\n");
835cc0c8	216
041b78f2 AB	217	elts = kmalloc(sizeof(void ) TEST_LIST_LEN, GFP_KERNEL);
	218	if (!elts) {
	219	printk(KERN_ERR "list_sort_test: error: cannot allocate "
	220	"memory\n");
	221	goto exit;
	222	}
	223
eeee9ebb	224	for (i = 0; i < TEST_LIST_LEN; i++) {
f3dc0e38 AB	225	el = kmalloc(sizeof(*el), GFP_KERNEL);
f3dc0e38 AB	226	if (!el) {
014afa94	227	printk(KERN_ERR "list_sort_test: error: cannot "
f3dc0e38 AB	228	"allocate memory\n");
	229	goto exit;
	230	}
835cc0c8	231	/* force some equivalencies */
f39fee5f	232	el->value = prandom_u32() % (TEST_LIST_LEN / 3);
835cc0c8	233	el->serial = i;
041b78f2 AB	234	el->poison1 = TEST_POISON1;
	235	el->poison2 = TEST_POISON2;
	236	elts[i] = el;
f3dc0e38	237	list_add_tail(&el->list, &head);
835cc0c8	238	}
835cc0c8	239
f3dc0e38 AB	240	list_sort(NULL, &head, cmp);
	241
	242	for (cur = head.next; cur->next != &head; cur = cur->next) {
	243	struct debug_el *el1;
	244	int cmp_result;
835cc0c8	245
835cc0c8	246	if (cur->next->prev != cur) {
014afa94 AB	247	printk(KERN_ERR "list_sort_test: error: list is "
014afa94 AB	248	"corrupted\n");
f3dc0e38 AB	249	goto exit;
	250	}
	251
	252	cmp_result = cmp(NULL, cur, cur->next);
	253	if (cmp_result > 0) {
014afa94 AB	254	printk(KERN_ERR "list_sort_test: error: list is not "
014afa94 AB	255	"sorted\n");
f3dc0e38 AB	256	goto exit;
	257	}
	258
	259	el = container_of(cur, struct debug_el, list);
	260	el1 = container_of(cur->next, struct debug_el, list);
	261	if (cmp_result == 0 && el->serial >= el1->serial) {
014afa94 AB	262	printk(KERN_ERR "list_sort_test: error: order of "
014afa94 AB	263	"equivalent elements not preserved\n");
f3dc0e38	264	goto exit;
835cc0c8	265	}
041b78f2 AB	266
	267	if (check(el, el1)) {
	268	printk(KERN_ERR "list_sort_test: error: element check "
	269	"failed\n");
	270	goto exit;
	271	}
835cc0c8 DM	272	count++;
835cc0c8 DM	273	}
f3dc0e38	274
eeee9ebb	275	if (count != TEST_LIST_LEN) {
014afa94 AB	276	printk(KERN_ERR "list_sort_test: error: bad list length %d",
014afa94 AB	277	count);
f3dc0e38 AB	278	goto exit;
	279	}
	280
	281	err = 0;
	282	exit:
041b78f2	283	kfree(elts);
f3dc0e38 AB	284	list_for_each_safe(cur, tmp, &head) {
	285	list_del(cur);
	286	kfree(container_of(cur, struct debug_el, list));
835cc0c8	287	}
f3dc0e38	288	return err;
835cc0c8 DM	289	}
835cc0c8 DM	290	module_init(list_sort_test);
6d411e6c	291	#endif /* CONFIG_TEST_LIST_SORT */