[linux.git] / lib / list_sort.c


#define pr_fmt(fmt) "list_sort_test: " fmt

#include <linux/kernel.h>
#include <linux/bug.h>
#include <linux/compiler.h>
#include <linux/export.h>
#include <linux/string.h>
#include <linux/list_sort.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;
	u8 count = 0;

	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.
		 */
		if (unlikely(!(++count)))
			(*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 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/slab.h>
#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) {
		pr_err("error: incorrect serial %d\n", ela->serial);
		return -EINVAL;
	}
	if (elb->serial >= TEST_LIST_LEN) {
		pr_err("error: incorrect serial %d\n", elb->serial);
		return -EINVAL;
	}
	if (elts[ela->serial] != ela || elts[elb->serial] != elb) {
		pr_err("error: phantom element\n");
		return -EINVAL;
	}
	if (ela->poison1 != TEST_POISON1 || ela->poison2 != TEST_POISON2) {
		pr_err("error: bad poison: %#x/%#x\n",
			ela->poison1, ela->poison2);
		return -EINVAL;
	}
	if (elb->poison1 != TEST_POISON1 || elb->poison2 != TEST_POISON2) {
		pr_err("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 = -ENOMEM;
	struct debug_el *el;
	struct list_head *cur;
	LIST_HEAD(head);

	pr_debug("start testing list_sort()\n");

	elts = kcalloc(TEST_LIST_LEN, sizeof(*elts), GFP_KERNEL);
	if (!elts) {
		pr_err("error: cannot allocate memory\n");
		return err;
	}

	for (i = 0; i < TEST_LIST_LEN; i++) {
		el = kmalloc(sizeof(*el), GFP_KERNEL);
		if (!el) {
			pr_err("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);

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

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

		cmp_result = cmp(NULL, cur, cur->next);
		if (cmp_result > 0) {
			pr_err("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) {
			pr_err("error: order of equivalent elements not "
				"preserved\n");
			goto exit;
		}

		if (check(el, el1)) {
			pr_err("error: element check failed\n");
			goto exit;
		}
		count++;
	}
	if (head.prev != cur) {
		pr_err("error: list is corrupted\n");
		goto exit;
	}


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

	err = 0;
exit:
	for (i = 0; i < TEST_LIST_LEN; i++)
		kfree(elts[i]);
	kfree(elts);
	return err;
}
late_initcall(list_sort_test);
#endif /* CONFIG_TEST_LIST_SORT */
Commit	Line	Data
d0da23b0 AM	1
	2	#define pr_fmt(fmt) "list_sort_test: " fmt
	3
2c761270	4	#include <linux/kernel.h>
7259fa04 RV	5	#include <linux/bug.h>
	6	#include <linux/compiler.h>
	7	#include <linux/export.h>
	8	#include <linux/string.h>
2c761270	9	#include <linux/list_sort.h>
2c761270 DC	10	#include <linux/list.h>
2c761270 DC	11
835cc0c8 DM	12	#define MAX_LIST_LENGTH_BITS 20
	13
	14	/*
	15	* Returns a list organized in an intermediate format suited
	16	* to chaining of merge() calls: null-terminated, no reserved or
	17	* sentinel head node, "prev" links not maintained.
	18	*/
	19	static struct list_head merge(void priv,
	20	int (cmp)(void priv, struct list_head *a,
	21	struct list_head *b),
	22	struct list_head a, struct list_head b)
	23	{
	24	struct list_head head, *tail = &head;
	25
	26	while (a && b) {
	27	/* if equal, take 'a' -- important for sort stability */
	28	if ((*cmp)(priv, a, b) <= 0) {
	29	tail->next = a;
	30	a = a->next;
	31	} else {
	32	tail->next = b;
	33	b = b->next;
	34	}
	35	tail = tail->next;
	36	}
	37	tail->next = a?:b;
	38	return head.next;
	39	}
	40
	41	/*
	42	* Combine final list merge with restoration of standard doubly-linked
	43	* list structure. This approach duplicates code from merge(), but
	44	* runs faster than the tidier alternatives of either a separate final
	45	* prev-link restoration pass, or maintaining the prev links
	46	* throughout.
	47	*/
	48	static void merge_and_restore_back_links(void *priv,
	49	int (cmp)(void priv, struct list_head *a,
	50	struct list_head *b),
	51	struct list_head *head,
	52	struct list_head a, struct list_head b)
	53	{
	54	struct list_head *tail = head;
61b3d6c4	55	u8 count = 0;
835cc0c8 DM	56
	57	while (a && b) {
	58	/* if equal, take 'a' -- important for sort stability */
	59	if ((*cmp)(priv, a, b) <= 0) {
	60	tail->next = a;
	61	a->prev = tail;
	62	a = a->next;
	63	} else {
	64	tail->next = b;
	65	b->prev = tail;
	66	b = b->next;
	67	}
	68	tail = tail->next;
	69	}
	70	tail->next = a ? : b;
	71
	72	do {
	73	/*
	74	* In worst cases this loop may run many iterations.
	75	* Continue callbacks to the client even though no
	76	* element comparison is needed, so the client's cmp()
	77	* routine can invoke cond_resched() periodically.
	78	*/
61b3d6c4 RV	79	if (unlikely(!(++count)))
61b3d6c4 RV	80	(*cmp)(priv, tail->next, tail->next);
835cc0c8 DM	81
	82	tail->next->prev = tail;
	83	tail = tail->next;
	84	} while (tail->next);
	85
	86	tail->next = head;
	87	head->prev = tail;
	88	}
	89
2c761270	90	/**
02b12b7a DM	91	* list_sort - sort a list
02b12b7a DM	92	* @priv: private data, opaque to list_sort(), passed to @cmp
2c761270 DC	93	* @head: the list to sort
	94	* @cmp: the elements comparison function
	95	*
02b12b7a DM	96	* This function implements "merge sort", which has O(nlog(n))
02b12b7a DM	97	* complexity.
2c761270	98	*
02b12b7a DM	99	* The comparison function @cmp must return a negative value if @a
	100	* should sort before @b, and a positive value if @a should sort after
	101	* @b. If @a and @b are equivalent, and their original relative
	102	* ordering is to be preserved, @cmp must return 0.
2c761270 DC	103	*/
2c761270 DC	104	void list_sort(void priv, struct list_head head,
835cc0c8 DM	105	int (cmp)(void priv, struct list_head *a,
835cc0c8 DM	106	struct list_head *b))
2c761270	107	{
835cc0c8 DM	108	struct list_head part[MAX_LIST_LENGTH_BITS+1]; / sorted partial lists
	109	-- last slot is a sentinel */
	110	int lev; /* index into part[] */
	111	int max_lev = 0;
	112	struct list_head *list;
2c761270 DC	113
	114	if (list_empty(head))
	115	return;
	116
835cc0c8 DM	117	memset(part, 0, sizeof(part));
	118
	119	head->prev->next = NULL;
2c761270	120	list = head->next;
2c761270	121
835cc0c8 DM	122	while (list) {
	123	struct list_head *cur = list;
	124	list = list->next;
	125	cur->next = NULL;
	126
	127	for (lev = 0; part[lev]; lev++) {
	128	cur = merge(priv, cmp, part[lev], cur);
	129	part[lev] = NULL;
	130	}
	131	if (lev > max_lev) {
	132	if (unlikely(lev >= ARRAY_SIZE(part)-1)) {
d0da23b0	133	printk_once(KERN_DEBUG "list too long for efficiency\n");
835cc0c8	134	lev--;
2c761270	135	}
835cc0c8	136	max_lev = lev;
2c761270	137	}
835cc0c8 DM	138	part[lev] = cur;
835cc0c8 DM	139	}
2c761270	140
835cc0c8 DM	141	for (lev = 0; lev < max_lev; lev++)
	142	if (part[lev])
	143	list = merge(priv, cmp, part[lev], list);
2c761270	144
835cc0c8 DM	145	merge_and_restore_back_links(priv, cmp, head, part[max_lev], list);
	146	}
	147	EXPORT_SYMBOL(list_sort);
2c761270	148
6d411e6c	149	#ifdef CONFIG_TEST_LIST_SORT
eeee9ebb	150
7259fa04	151	#include <linux/slab.h>
eeee9ebb AB	152	#include <linux/random.h>
eeee9ebb AB	153
041b78f2 AB	154	/*
	155	* The pattern of set bits in the list length determines which cases
	156	* are hit in list_sort().
	157	*/
	158	#define TEST_LIST_LEN (512+128+2) /* not including head */
	159
	160	#define TEST_POISON1 0xDEADBEEF
	161	#define TEST_POISON2 0xA324354C
	162
835cc0c8	163	struct debug_el {
041b78f2	164	unsigned int poison1;
eeee9ebb	165	struct list_head list;
041b78f2	166	unsigned int poison2;
835cc0c8 DM	167	int value;
	168	unsigned serial;
	169	};
2c761270	170
041b78f2 AB	171	/* Array, containing pointers to all elements in the test list */
	172	static struct debug_el **elts __initdata;
	173
	174	static int __init check(struct debug_el ela, struct debug_el elb)
835cc0c8	175	{
041b78f2	176	if (ela->serial >= TEST_LIST_LEN) {
d0da23b0	177	pr_err("error: incorrect serial %d\n", ela->serial);
041b78f2 AB	178	return -EINVAL;
	179	}
	180	if (elb->serial >= TEST_LIST_LEN) {
d0da23b0	181	pr_err("error: incorrect serial %d\n", elb->serial);
041b78f2 AB	182	return -EINVAL;
	183	}
	184	if (elts[ela->serial] != ela \|\| elts[elb->serial] != elb) {
d0da23b0	185	pr_err("error: phantom element\n");
041b78f2 AB	186	return -EINVAL;
	187	}
	188	if (ela->poison1 != TEST_POISON1 \|\| ela->poison2 != TEST_POISON2) {
d0da23b0 AM	189	pr_err("error: bad poison: %#x/%#x\n",
d0da23b0 AM	190	ela->poison1, ela->poison2);
041b78f2 AB	191	return -EINVAL;
	192	}
	193	if (elb->poison1 != TEST_POISON1 \|\| elb->poison2 != TEST_POISON2) {
d0da23b0 AM	194	pr_err("error: bad poison: %#x/%#x\n",
d0da23b0 AM	195	elb->poison1, elb->poison2);
041b78f2 AB	196	return -EINVAL;
	197	}
	198	return 0;
2c761270 DC	199	}
2c761270 DC	200
041b78f2 AB	201	static int __init cmp(void priv, struct list_head a, struct list_head *b)
	202	{
	203	struct debug_el ela, elb;
	204
	205	ela = container_of(a, struct debug_el, list);
	206	elb = container_of(b, struct debug_el, list);
	207
	208	check(ela, elb);
	209	return ela->value - elb->value;
	210	}
835cc0c8 DM	211
	212	static int __init list_sort_test(void)
	213	{
27d555d1	214	int i, count = 1, err = -ENOMEM;
f3dc0e38	215	struct debug_el *el;
69412303	216	struct list_head *cur;
f3dc0e38	217	LIST_HEAD(head);
835cc0c8	218
d0da23b0	219	pr_debug("start testing list_sort()\n");
835cc0c8	220
69412303	221	elts = kcalloc(TEST_LIST_LEN, sizeof(*elts), GFP_KERNEL);
041b78f2	222	if (!elts) {
d0da23b0	223	pr_err("error: cannot allocate memory\n");
69412303	224	return err;
041b78f2 AB	225	}
041b78f2 AB	226
eeee9ebb	227	for (i = 0; i < TEST_LIST_LEN; i++) {
f3dc0e38 AB	228	el = kmalloc(sizeof(*el), GFP_KERNEL);
f3dc0e38 AB	229	if (!el) {
d0da23b0	230	pr_err("error: cannot allocate memory\n");
f3dc0e38 AB	231	goto exit;
f3dc0e38 AB	232	}
835cc0c8	233	/* force some equivalencies */
f39fee5f	234	el->value = prandom_u32() % (TEST_LIST_LEN / 3);
835cc0c8	235	el->serial = i;
041b78f2 AB	236	el->poison1 = TEST_POISON1;
	237	el->poison2 = TEST_POISON2;
	238	elts[i] = el;
f3dc0e38	239	list_add_tail(&el->list, &head);
835cc0c8	240	}
835cc0c8	241
f3dc0e38 AB	242	list_sort(NULL, &head, cmp);
f3dc0e38 AB	243
27d555d1	244	err = -EINVAL;
f3dc0e38 AB	245	for (cur = head.next; cur->next != &head; cur = cur->next) {
	246	struct debug_el *el1;
	247	int cmp_result;
835cc0c8	248
835cc0c8	249	if (cur->next->prev != cur) {
d0da23b0	250	pr_err("error: list is corrupted\n");
f3dc0e38 AB	251	goto exit;
	252	}
	253
	254	cmp_result = cmp(NULL, cur, cur->next);
	255	if (cmp_result > 0) {
d0da23b0	256	pr_err("error: list is not sorted\n");
f3dc0e38 AB	257	goto exit;
	258	}
	259
	260	el = container_of(cur, struct debug_el, list);
	261	el1 = container_of(cur->next, struct debug_el, list);
	262	if (cmp_result == 0 && el->serial >= el1->serial) {
d0da23b0 AM	263	pr_err("error: order of equivalent elements not "
d0da23b0 AM	264	"preserved\n");
f3dc0e38	265	goto exit;
835cc0c8	266	}
041b78f2 AB	267
041b78f2 AB	268	if (check(el, el1)) {
d0da23b0	269	pr_err("error: element check failed\n");
041b78f2 AB	270	goto exit;
041b78f2 AB	271	}
835cc0c8 DM	272	count++;
835cc0c8 DM	273	}
9d418dcc	274	if (head.prev != cur) {
d0da23b0	275	pr_err("error: list is corrupted\n");
9d418dcc RV	276	goto exit;
	277	}
	278
f3dc0e38	279
eeee9ebb	280	if (count != TEST_LIST_LEN) {
d0da23b0	281	pr_err("error: bad list length %d", count);
f3dc0e38 AB	282	goto exit;
	283	}
	284
	285	err = 0;
	286	exit:
69412303 RV	287	for (i = 0; i < TEST_LIST_LEN; i++)
69412303 RV	288	kfree(elts[i]);
041b78f2	289	kfree(elts);
f3dc0e38	290	return err;
835cc0c8	291	}
4c7217f1	292	late_initcall(list_sort_test);
6d411e6c	293	#endif /* CONFIG_TEST_LIST_SORT */