[mirror_ubuntu-artful-kernel.git] / lib / list_sort.c


#define pr_fmt(fmt) "list_sort_test: " fmt

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