The 'lib_sort()' test does not free memory if it fails, and it makes the kernel panic if it cannot allocate memory. This patch fixes the problem. This patch also changes several small things: o use 'list_add()' helper instead of adding manually o introduce temporary 'el1' variable to avoid ugly and unreadalbe "if" statement o make 'head' to be stack variable instead of 'kmalloc()'ed, which simplifies code a bit Overall, this patch is of clean-up type. Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com> Cc: Don Mullis <don.mullis@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
231 lines
5.5 KiB
C
231 lines
5.5 KiB
C
#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/list_sort.h>
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#include <linux/slab.h>
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#include <linux/list.h>
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#define MAX_LIST_LENGTH_BITS 20
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/*
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* Returns a list organized in an intermediate format suited
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* to chaining of merge() calls: null-terminated, no reserved or
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* sentinel head node, "prev" links not maintained.
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*/
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static struct list_head *merge(void *priv,
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int (*cmp)(void *priv, struct list_head *a,
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struct list_head *b),
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struct list_head *a, struct list_head *b)
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{
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struct list_head head, *tail = &head;
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while (a && b) {
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/* if equal, take 'a' -- important for sort stability */
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if ((*cmp)(priv, a, b) <= 0) {
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tail->next = a;
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a = a->next;
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} else {
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tail->next = b;
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b = b->next;
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}
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tail = tail->next;
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}
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tail->next = a?:b;
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return head.next;
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}
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/*
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* Combine final list merge with restoration of standard doubly-linked
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* list structure. This approach duplicates code from merge(), but
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* runs faster than the tidier alternatives of either a separate final
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* prev-link restoration pass, or maintaining the prev links
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* throughout.
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*/
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static void merge_and_restore_back_links(void *priv,
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int (*cmp)(void *priv, struct list_head *a,
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struct list_head *b),
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struct list_head *head,
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struct list_head *a, struct list_head *b)
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{
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struct list_head *tail = head;
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while (a && b) {
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/* if equal, take 'a' -- important for sort stability */
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if ((*cmp)(priv, a, b) <= 0) {
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tail->next = a;
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a->prev = tail;
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a = a->next;
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} else {
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tail->next = b;
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b->prev = tail;
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b = b->next;
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}
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tail = tail->next;
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}
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tail->next = a ? : b;
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do {
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/*
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* In worst cases this loop may run many iterations.
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* Continue callbacks to the client even though no
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* element comparison is needed, so the client's cmp()
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* routine can invoke cond_resched() periodically.
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*/
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(*cmp)(priv, tail->next, tail->next);
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tail->next->prev = tail;
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tail = tail->next;
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} while (tail->next);
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tail->next = head;
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head->prev = tail;
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}
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/**
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* list_sort - sort a list
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* @priv: private data, opaque to list_sort(), passed to @cmp
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* @head: the list to sort
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* @cmp: the elements comparison function
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*
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* This function implements "merge sort", which has O(nlog(n))
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* complexity.
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*
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* The comparison function @cmp must return a negative value if @a
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* should sort before @b, and a positive value if @a should sort after
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* @b. If @a and @b are equivalent, and their original relative
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* ordering is to be preserved, @cmp must return 0.
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*/
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void list_sort(void *priv, struct list_head *head,
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int (*cmp)(void *priv, struct list_head *a,
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struct list_head *b))
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{
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struct list_head *part[MAX_LIST_LENGTH_BITS+1]; /* sorted partial lists
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-- last slot is a sentinel */
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int lev; /* index into part[] */
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int max_lev = 0;
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struct list_head *list;
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if (list_empty(head))
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return;
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memset(part, 0, sizeof(part));
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head->prev->next = NULL;
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list = head->next;
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while (list) {
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struct list_head *cur = list;
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list = list->next;
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cur->next = NULL;
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for (lev = 0; part[lev]; lev++) {
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cur = merge(priv, cmp, part[lev], cur);
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part[lev] = NULL;
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}
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if (lev > max_lev) {
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if (unlikely(lev >= ARRAY_SIZE(part)-1)) {
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printk_once(KERN_DEBUG "list passed to"
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" list_sort() too long for"
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" efficiency\n");
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lev--;
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}
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max_lev = lev;
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}
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part[lev] = cur;
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}
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for (lev = 0; lev < max_lev; lev++)
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if (part[lev])
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list = merge(priv, cmp, part[lev], list);
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merge_and_restore_back_links(priv, cmp, head, part[max_lev], list);
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}
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EXPORT_SYMBOL(list_sort);
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#ifdef CONFIG_TEST_LIST_SORT
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#include <linux/random.h>
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struct debug_el {
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struct list_head list;
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int value;
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unsigned serial;
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};
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static int cmp(void *priv, struct list_head *a, struct list_head *b)
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{
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return container_of(a, struct debug_el, list)->value
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- container_of(b, struct debug_el, list)->value;
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}
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/*
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* The pattern of set bits in the list length determines which cases
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* are hit in list_sort().
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*/
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#define TEST_LIST_LEN (512+128+2) /* not including head */
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static int __init list_sort_test(void)
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{
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int i, count = 1, err = -EINVAL;
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struct debug_el *el;
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struct list_head *cur, *tmp;
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LIST_HEAD(head);
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printk(KERN_DEBUG "testing list_sort()\n");
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for (i = 0; i < TEST_LIST_LEN; i++) {
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el = kmalloc(sizeof(*el), GFP_KERNEL);
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if (!el) {
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printk(KERN_ERR "cancel list_sort() testing - cannot "
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"allocate memory\n");
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goto exit;
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}
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/* force some equivalencies */
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el->value = random32() % (TEST_LIST_LEN/3);
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el->serial = i;
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list_add_tail(&el->list, &head);
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}
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list_sort(NULL, &head, cmp);
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for (cur = head.next; cur->next != &head; cur = cur->next) {
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struct debug_el *el1;
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int cmp_result;
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if (cur->next->prev != cur) {
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printk(KERN_ERR "list_sort() returned "
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"a corrupted list!\n");
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goto exit;
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}
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cmp_result = cmp(NULL, cur, cur->next);
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if (cmp_result > 0) {
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printk(KERN_ERR "list_sort() failed to sort!\n");
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goto exit;
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}
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el = container_of(cur, struct debug_el, list);
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el1 = container_of(cur->next, struct debug_el, list);
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if (cmp_result == 0 && el->serial >= el1->serial) {
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printk(KERN_ERR "list_sort() failed to preserve order "
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"of equivalent elements!\n");
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goto exit;
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}
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count++;
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}
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if (count != TEST_LIST_LEN) {
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printk(KERN_ERR "list_sort() returned list of "
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"different length!\n");
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goto exit;
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}
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err = 0;
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exit:
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list_for_each_safe(cur, tmp, &head) {
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list_del(cur);
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kfree(container_of(cur, struct debug_el, list));
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}
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return err;
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}
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module_init(list_sort_test);
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#endif /* CONFIG_TEST_LIST_SORT */
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