1/* SPDX-License-Identifier: GPL-2.0 */
2#ifndef _LINUX_LIST_H
3#define _LINUX_LIST_H
4
5#include <linux/container_of.h>
6#include <linux/types.h>
7#include <linux/stddef.h>
8#include <linux/poison.h>
9#include <linux/const.h>
10
11#include <asm/barrier.h>
12
13/*
14 * Circular doubly linked list implementation.
15 *
16 * Some of the internal functions ("__xxx") are useful when
17 * manipulating whole lists rather than single entries, as
18 * sometimes we already know the next/prev entries and we can
19 * generate better code by using them directly rather than
20 * using the generic single-entry routines.
21 */
22
23/**
24 * LIST_HEAD_INIT - initialize a &struct list_head's links to point to itself
25 * @name: name of the list_head
26 */
27#define LIST_HEAD_INIT(name) { &(name), &(name) }
28
29/**
30 * LIST_HEAD - definition of a &struct list_head with initialization values
31 * @name: name of the list_head
32 */
33#define LIST_HEAD(name) \
34 struct list_head name = LIST_HEAD_INIT(name)
35
36/**
37 * INIT_LIST_HEAD - Initialize a list_head structure
38 * @list: list_head structure to be initialized.
39 *
40 * Initializes the list_head to point to itself. If it is a list header,
41 * the result is an empty list.
42 */
43static inline void INIT_LIST_HEAD(struct list_head *list)
44{
45 WRITE_ONCE(list->next, list);
46 WRITE_ONCE(list->prev, list);
47}
48
49#ifdef CONFIG_LIST_HARDENED
50
51#ifdef CONFIG_DEBUG_LIST
52# define __list_valid_slowpath
53#else
54# define __list_valid_slowpath __cold __preserve_most
55#endif
56
57/*
58 * Performs the full set of list corruption checks before __list_add().
59 * On list corruption reports a warning, and returns false.
60 */
61bool __list_valid_slowpath __list_add_valid_or_report(struct list_head *new,
62 struct list_head *prev,
63 struct list_head *next);
64
65/*
66 * Performs list corruption checks before __list_add(). Returns false if a
67 * corruption is detected, true otherwise.
68 *
69 * With CONFIG_LIST_HARDENED only, performs minimal list integrity checking
70 * inline to catch non-faulting corruptions, and only if a corruption is
71 * detected calls the reporting function __list_add_valid_or_report().
72 */
73static __always_inline bool __list_add_valid(struct list_head *new,
74 struct list_head *prev,
75 struct list_head *next)
76{
77 bool ret = true;
78
79 if (!IS_ENABLED(CONFIG_DEBUG_LIST)) {
80 /*
81 * With the hardening version, elide checking if next and prev
82 * are NULL, since the immediate dereference of them below would
83 * result in a fault if NULL.
84 *
85 * With the reduced set of checks, we can afford to inline the
86 * checks, which also gives the compiler a chance to elide some
87 * of them completely if they can be proven at compile-time. If
88 * one of the pre-conditions does not hold, the slow-path will
89 * show a report which pre-condition failed.
90 */
91 if (likely(next->prev == prev && prev->next == next && new != prev && new != next))
92 return true;
93 ret = false;
94 }
95
96 ret &= __list_add_valid_or_report(new, prev, next);
97 return ret;
98}
99
100/*
101 * Performs the full set of list corruption checks before __list_del_entry().
102 * On list corruption reports a warning, and returns false.
103 */
104bool __list_valid_slowpath __list_del_entry_valid_or_report(struct list_head *entry);
105
106/*
107 * Performs list corruption checks before __list_del_entry(). Returns false if a
108 * corruption is detected, true otherwise.
109 *
110 * With CONFIG_LIST_HARDENED only, performs minimal list integrity checking
111 * inline to catch non-faulting corruptions, and only if a corruption is
112 * detected calls the reporting function __list_del_entry_valid_or_report().
113 */
114static __always_inline bool __list_del_entry_valid(struct list_head *entry)
115{
116 bool ret = true;
117
118 if (!IS_ENABLED(CONFIG_DEBUG_LIST)) {
119 struct list_head *prev = entry->prev;
120 struct list_head *next = entry->next;
121
122 /*
123 * With the hardening version, elide checking if next and prev
124 * are NULL, LIST_POISON1 or LIST_POISON2, since the immediate
125 * dereference of them below would result in a fault.
126 */
127 if (likely(prev->next == entry && next->prev == entry))
128 return true;
129 ret = false;
130 }
131
132 ret &= __list_del_entry_valid_or_report(entry);
133 return ret;
134}
135#else
136static inline bool __list_add_valid(struct list_head *new,
137 struct list_head *prev,
138 struct list_head *next)
139{
140 return true;
141}
142static inline bool __list_del_entry_valid(struct list_head *entry)
143{
144 return true;
145}
146#endif
147
148/*
149 * Insert a new entry between two known consecutive entries.
150 *
151 * This is only for internal list manipulation where we know
152 * the prev/next entries already!
153 */
154static inline void __list_add(struct list_head *new,
155 struct list_head *prev,
156 struct list_head *next)
157{
158 if (!__list_add_valid(new, prev, next))
159 return;
160
161 next->prev = new;
162 new->next = next;
163 new->prev = prev;
164 WRITE_ONCE(prev->next, new);
165}
166
167/**
168 * list_add - add a new entry
169 * @new: new entry to be added
170 * @head: list head to add it after
171 *
172 * Insert a new entry after the specified head.
173 * This is good for implementing stacks.
174 */
175static inline void list_add(struct list_head *new, struct list_head *head)
176{
177 __list_add(new, prev: head, next: head->next);
178}
179
180
181/**
182 * list_add_tail - add a new entry
183 * @new: new entry to be added
184 * @head: list head to add it before
185 *
186 * Insert a new entry before the specified head.
187 * This is useful for implementing queues.
188 */
189static inline void list_add_tail(struct list_head *new, struct list_head *head)
190{
191 __list_add(new, prev: head->prev, next: head);
192}
193
194/*
195 * Delete a list entry by making the prev/next entries
196 * point to each other.
197 *
198 * This is only for internal list manipulation where we know
199 * the prev/next entries already!
200 */
201static inline void __list_del(struct list_head * prev, struct list_head * next)
202{
203 next->prev = prev;
204 WRITE_ONCE(prev->next, next);
205}
206
207/*
208 * Delete a list entry and clear the 'prev' pointer.
209 *
210 * This is a special-purpose list clearing method used in the networking code
211 * for lists allocated as per-cpu, where we don't want to incur the extra
212 * WRITE_ONCE() overhead of a regular list_del_init(). The code that uses this
213 * needs to check the node 'prev' pointer instead of calling list_empty().
214 */
215static inline void __list_del_clearprev(struct list_head *entry)
216{
217 __list_del(prev: entry->prev, next: entry->next);
218 entry->prev = NULL;
219}
220
221static inline void __list_del_entry(struct list_head *entry)
222{
223 if (!__list_del_entry_valid(entry))
224 return;
225
226 __list_del(prev: entry->prev, next: entry->next);
227}
228
229/**
230 * list_del - deletes entry from list.
231 * @entry: the element to delete from the list.
232 * Note: list_empty() on entry does not return true after this, the entry is
233 * in an undefined state.
234 */
235static inline void list_del(struct list_head *entry)
236{
237 __list_del_entry(entry);
238 entry->next = LIST_POISON1;
239 entry->prev = LIST_POISON2;
240}
241
242/**
243 * list_replace - replace old entry by new one
244 * @old : the element to be replaced
245 * @new : the new element to insert
246 *
247 * If @old was empty, it will be overwritten.
248 */
249static inline void list_replace(struct list_head *old,
250 struct list_head *new)
251{
252 new->next = old->next;
253 new->next->prev = new;
254 new->prev = old->prev;
255 new->prev->next = new;
256}
257
258/**
259 * list_replace_init - replace old entry by new one and initialize the old one
260 * @old : the element to be replaced
261 * @new : the new element to insert
262 *
263 * If @old was empty, it will be overwritten.
264 */
265static inline void list_replace_init(struct list_head *old,
266 struct list_head *new)
267{
268 list_replace(old, new);
269 INIT_LIST_HEAD(list: old);
270}
271
272/**
273 * list_swap - replace entry1 with entry2 and re-add entry1 at entry2's position
274 * @entry1: the location to place entry2
275 * @entry2: the location to place entry1
276 */
277static inline void list_swap(struct list_head *entry1,
278 struct list_head *entry2)
279{
280 struct list_head *pos = entry2->prev;
281
282 list_del(entry: entry2);
283 list_replace(old: entry1, new: entry2);
284 if (pos == entry1)
285 pos = entry2;
286 list_add(new: entry1, head: pos);
287}
288
289/**
290 * list_del_init - deletes entry from list and reinitialize it.
291 * @entry: the element to delete from the list.
292 */
293static inline void list_del_init(struct list_head *entry)
294{
295 __list_del_entry(entry);
296 INIT_LIST_HEAD(list: entry);
297}
298
299/**
300 * list_move - delete from one list and add as another's head
301 * @list: the entry to move
302 * @head: the head that will precede our entry
303 */
304static inline void list_move(struct list_head *list, struct list_head *head)
305{
306 __list_del_entry(entry: list);
307 list_add(new: list, head);
308}
309
310/**
311 * list_move_tail - delete from one list and add as another's tail
312 * @list: the entry to move
313 * @head: the head that will follow our entry
314 */
315static inline void list_move_tail(struct list_head *list,
316 struct list_head *head)
317{
318 __list_del_entry(entry: list);
319 list_add_tail(new: list, head);
320}
321
322/**
323 * list_bulk_move_tail - move a subsection of a list to its tail
324 * @head: the head that will follow our entry
325 * @first: first entry to move
326 * @last: last entry to move, can be the same as first
327 *
328 * Move all entries between @first and including @last before @head.
329 * All three entries must belong to the same linked list.
330 */
331static inline void list_bulk_move_tail(struct list_head *head,
332 struct list_head *first,
333 struct list_head *last)
334{
335 first->prev->next = last->next;
336 last->next->prev = first->prev;
337
338 head->prev->next = first;
339 first->prev = head->prev;
340
341 last->next = head;
342 head->prev = last;
343}
344
345/**
346 * list_is_first -- tests whether @list is the first entry in list @head
347 * @list: the entry to test
348 * @head: the head of the list
349 */
350static inline int list_is_first(const struct list_head *list, const struct list_head *head)
351{
352 return list->prev == head;
353}
354
355/**
356 * list_is_last - tests whether @list is the last entry in list @head
357 * @list: the entry to test
358 * @head: the head of the list
359 */
360static inline int list_is_last(const struct list_head *list, const struct list_head *head)
361{
362 return list->next == head;
363}
364
365/**
366 * list_is_head - tests whether @list is the list @head
367 * @list: the entry to test
368 * @head: the head of the list
369 */
370static inline int list_is_head(const struct list_head *list, const struct list_head *head)
371{
372 return list == head;
373}
374
375/**
376 * list_empty - tests whether a list is empty
377 * @head: the list to test.
378 */
379static inline int list_empty(const struct list_head *head)
380{
381 return READ_ONCE(head->next) == head;
382}
383
384/**
385 * list_del_init_careful - deletes entry from list and reinitialize it.
386 * @entry: the element to delete from the list.
387 *
388 * This is the same as list_del_init(), except designed to be used
389 * together with list_empty_careful() in a way to guarantee ordering
390 * of other memory operations.
391 *
392 * Any memory operations done before a list_del_init_careful() are
393 * guaranteed to be visible after a list_empty_careful() test.
394 */
395static inline void list_del_init_careful(struct list_head *entry)
396{
397 __list_del_entry(entry);
398 WRITE_ONCE(entry->prev, entry);
399 smp_store_release(&entry->next, entry);
400}
401
402/**
403 * list_empty_careful - tests whether a list is empty and not being modified
404 * @head: the list to test
405 *
406 * Description:
407 * tests whether a list is empty _and_ checks that no other CPU might be
408 * in the process of modifying either member (next or prev)
409 *
410 * NOTE: using list_empty_careful() without synchronization
411 * can only be safe if the only activity that can happen
412 * to the list entry is list_del_init(). Eg. it cannot be used
413 * if another CPU could re-list_add() it.
414 */
415static inline int list_empty_careful(const struct list_head *head)
416{
417 struct list_head *next = smp_load_acquire(&head->next);
418 return list_is_head(list: next, head) && (next == READ_ONCE(head->prev));
419}
420
421/**
422 * list_rotate_left - rotate the list to the left
423 * @head: the head of the list
424 */
425static inline void list_rotate_left(struct list_head *head)
426{
427 struct list_head *first;
428
429 if (!list_empty(head)) {
430 first = head->next;
431 list_move_tail(list: first, head);
432 }
433}
434
435/**
436 * list_rotate_to_front() - Rotate list to specific item.
437 * @list: The desired new front of the list.
438 * @head: The head of the list.
439 *
440 * Rotates list so that @list becomes the new front of the list.
441 */
442static inline void list_rotate_to_front(struct list_head *list,
443 struct list_head *head)
444{
445 /*
446 * Deletes the list head from the list denoted by @head and
447 * places it as the tail of @list, this effectively rotates the
448 * list so that @list is at the front.
449 */
450 list_move_tail(list: head, head: list);
451}
452
453/**
454 * list_is_singular - tests whether a list has just one entry.
455 * @head: the list to test.
456 */
457static inline int list_is_singular(const struct list_head *head)
458{
459 return !list_empty(head) && (head->next == head->prev);
460}
461
462static inline void __list_cut_position(struct list_head *list,
463 struct list_head *head, struct list_head *entry)
464{
465 struct list_head *new_first = entry->next;
466 list->next = head->next;
467 list->next->prev = list;
468 list->prev = entry;
469 entry->next = list;
470 head->next = new_first;
471 new_first->prev = head;
472}
473
474/**
475 * list_cut_position - cut a list into two
476 * @list: a new list to add all removed entries
477 * @head: a list with entries
478 * @entry: an entry within head, could be the head itself
479 * and if so we won't cut the list
480 *
481 * This helper moves the initial part of @head, up to and
482 * including @entry, from @head to @list. You should
483 * pass on @entry an element you know is on @head. @list
484 * should be an empty list or a list you do not care about
485 * losing its data.
486 *
487 */
488static inline void list_cut_position(struct list_head *list,
489 struct list_head *head, struct list_head *entry)
490{
491 if (list_empty(head))
492 return;
493 if (list_is_singular(head) && !list_is_head(list: entry, head) && (entry != head->next))
494 return;
495 if (list_is_head(list: entry, head))
496 INIT_LIST_HEAD(list);
497 else
498 __list_cut_position(list, head, entry);
499}
500
501/**
502 * list_cut_before - cut a list into two, before given entry
503 * @list: a new list to add all removed entries
504 * @head: a list with entries
505 * @entry: an entry within head, could be the head itself
506 *
507 * This helper moves the initial part of @head, up to but
508 * excluding @entry, from @head to @list. You should pass
509 * in @entry an element you know is on @head. @list should
510 * be an empty list or a list you do not care about losing
511 * its data.
512 * If @entry == @head, all entries on @head are moved to
513 * @list.
514 */
515static inline void list_cut_before(struct list_head *list,
516 struct list_head *head,
517 struct list_head *entry)
518{
519 if (head->next == entry) {
520 INIT_LIST_HEAD(list);
521 return;
522 }
523 list->next = head->next;
524 list->next->prev = list;
525 list->prev = entry->prev;
526 list->prev->next = list;
527 head->next = entry;
528 entry->prev = head;
529}
530
531static inline void __list_splice(const struct list_head *list,
532 struct list_head *prev,
533 struct list_head *next)
534{
535 struct list_head *first = list->next;
536 struct list_head *last = list->prev;
537
538 first->prev = prev;
539 prev->next = first;
540
541 last->next = next;
542 next->prev = last;
543}
544
545/**
546 * list_splice - join two lists, this is designed for stacks
547 * @list: the new list to add.
548 * @head: the place to add it in the first list.
549 */
550static inline void list_splice(const struct list_head *list,
551 struct list_head *head)
552{
553 if (!list_empty(head: list))
554 __list_splice(list, prev: head, next: head->next);
555}
556
557/**
558 * list_splice_tail - join two lists, each list being a queue
559 * @list: the new list to add.
560 * @head: the place to add it in the first list.
561 */
562static inline void list_splice_tail(struct list_head *list,
563 struct list_head *head)
564{
565 if (!list_empty(head: list))
566 __list_splice(list, prev: head->prev, next: head);
567}
568
569/**
570 * list_splice_init - join two lists and reinitialise the emptied list.
571 * @list: the new list to add.
572 * @head: the place to add it in the first list.
573 *
574 * The list at @list is reinitialised
575 */
576static inline void list_splice_init(struct list_head *list,
577 struct list_head *head)
578{
579 if (!list_empty(head: list)) {
580 __list_splice(list, prev: head, next: head->next);
581 INIT_LIST_HEAD(list);
582 }
583}
584
585/**
586 * list_splice_tail_init - join two lists and reinitialise the emptied list
587 * @list: the new list to add.
588 * @head: the place to add it in the first list.
589 *
590 * Each of the lists is a queue.
591 * The list at @list is reinitialised
592 */
593static inline void list_splice_tail_init(struct list_head *list,
594 struct list_head *head)
595{
596 if (!list_empty(head: list)) {
597 __list_splice(list, prev: head->prev, next: head);
598 INIT_LIST_HEAD(list);
599 }
600}
601
602/**
603 * list_entry - get the struct for this entry
604 * @ptr: the &struct list_head pointer.
605 * @type: the type of the struct this is embedded in.
606 * @member: the name of the list_head within the struct.
607 */
608#define list_entry(ptr, type, member) \
609 container_of(ptr, type, member)
610
611/**
612 * list_first_entry - get the first element from a list
613 * @ptr: the list head to take the element from.
614 * @type: the type of the struct this is embedded in.
615 * @member: the name of the list_head within the struct.
616 *
617 * Note, that list is expected to be not empty.
618 */
619#define list_first_entry(ptr, type, member) \
620 list_entry((ptr)->next, type, member)
621
622/**
623 * list_last_entry - get the last element from a list
624 * @ptr: the list head to take the element from.
625 * @type: the type of the struct this is embedded in.
626 * @member: the name of the list_head within the struct.
627 *
628 * Note, that list is expected to be not empty.
629 */
630#define list_last_entry(ptr, type, member) \
631 list_entry((ptr)->prev, type, member)
632
633/**
634 * list_first_entry_or_null - get the first element from a list
635 * @ptr: the list head to take the element from.
636 * @type: the type of the struct this is embedded in.
637 * @member: the name of the list_head within the struct.
638 *
639 * Note that if the list is empty, it returns NULL.
640 */
641#define list_first_entry_or_null(ptr, type, member) ({ \
642 struct list_head *head__ = (ptr); \
643 struct list_head *pos__ = READ_ONCE(head__->next); \
644 pos__ != head__ ? list_entry(pos__, type, member) : NULL; \
645})
646
647/**
648 * list_last_entry_or_null - get the last element from a list
649 * @ptr: the list head to take the element from.
650 * @type: the type of the struct this is embedded in.
651 * @member: the name of the list_head within the struct.
652 *
653 * Note that if the list is empty, it returns NULL.
654 */
655#define list_last_entry_or_null(ptr, type, member) ({ \
656 struct list_head *head__ = (ptr); \
657 struct list_head *pos__ = READ_ONCE(head__->prev); \
658 pos__ != head__ ? list_entry(pos__, type, member) : NULL; \
659})
660
661/**
662 * list_next_entry - get the next element in list
663 * @pos: the type * to cursor
664 * @member: the name of the list_head within the struct.
665 */
666#define list_next_entry(pos, member) \
667 list_entry((pos)->member.next, typeof(*(pos)), member)
668
669/**
670 * list_next_entry_circular - get the next element in list
671 * @pos: the type * to cursor.
672 * @head: the list head to take the element from.
673 * @member: the name of the list_head within the struct.
674 *
675 * Wraparound if pos is the last element (return the first element).
676 * Note, that list is expected to be not empty.
677 */
678#define list_next_entry_circular(pos, head, member) \
679 (list_is_last(&(pos)->member, head) ? \
680 list_first_entry(head, typeof(*(pos)), member) : list_next_entry(pos, member))
681
682/**
683 * list_prev_entry - get the prev element in list
684 * @pos: the type * to cursor
685 * @member: the name of the list_head within the struct.
686 */
687#define list_prev_entry(pos, member) \
688 list_entry((pos)->member.prev, typeof(*(pos)), member)
689
690/**
691 * list_prev_entry_circular - get the prev element in list
692 * @pos: the type * to cursor.
693 * @head: the list head to take the element from.
694 * @member: the name of the list_head within the struct.
695 *
696 * Wraparound if pos is the first element (return the last element).
697 * Note, that list is expected to be not empty.
698 */
699#define list_prev_entry_circular(pos, head, member) \
700 (list_is_first(&(pos)->member, head) ? \
701 list_last_entry(head, typeof(*(pos)), member) : list_prev_entry(pos, member))
702
703/**
704 * list_for_each - iterate over a list
705 * @pos: the &struct list_head to use as a loop cursor.
706 * @head: the head for your list.
707 */
708#define list_for_each(pos, head) \
709 for (pos = (head)->next; !list_is_head(pos, (head)); pos = pos->next)
710
711/**
712 * list_for_each_continue - continue iteration over a list
713 * @pos: the &struct list_head to use as a loop cursor.
714 * @head: the head for your list.
715 *
716 * Continue to iterate over a list, continuing after the current position.
717 */
718#define list_for_each_continue(pos, head) \
719 for (pos = pos->next; !list_is_head(pos, (head)); pos = pos->next)
720
721/**
722 * list_for_each_prev - iterate over a list backwards
723 * @pos: the &struct list_head to use as a loop cursor.
724 * @head: the head for your list.
725 */
726#define list_for_each_prev(pos, head) \
727 for (pos = (head)->prev; !list_is_head(pos, (head)); pos = pos->prev)
728
729/**
730 * list_for_each_safe - iterate over a list safe against removal of list entry
731 * @pos: the &struct list_head to use as a loop cursor.
732 * @n: another &struct list_head to use as temporary storage
733 * @head: the head for your list.
734 */
735#define list_for_each_safe(pos, n, head) \
736 for (pos = (head)->next, n = pos->next; \
737 !list_is_head(pos, (head)); \
738 pos = n, n = pos->next)
739
740/**
741 * list_for_each_prev_safe - iterate over a list backwards safe against removal of list entry
742 * @pos: the &struct list_head to use as a loop cursor.
743 * @n: another &struct list_head to use as temporary storage
744 * @head: the head for your list.
745 */
746#define list_for_each_prev_safe(pos, n, head) \
747 for (pos = (head)->prev, n = pos->prev; \
748 !list_is_head(pos, (head)); \
749 pos = n, n = pos->prev)
750
751/**
752 * list_count_nodes - count nodes in the list
753 * @head: the head for your list.
754 */
755static inline size_t list_count_nodes(struct list_head *head)
756{
757 struct list_head *pos;
758 size_t count = 0;
759
760 list_for_each(pos, head)
761 count++;
762
763 return count;
764}
765
766/**
767 * list_entry_is_head - test if the entry points to the head of the list
768 * @pos: the type * to cursor
769 * @head: the head for your list.
770 * @member: the name of the list_head within the struct.
771 */
772#define list_entry_is_head(pos, head, member) \
773 list_is_head(&pos->member, (head))
774
775/**
776 * list_for_each_entry - iterate over list of given type
777 * @pos: the type * to use as a loop cursor.
778 * @head: the head for your list.
779 * @member: the name of the list_head within the struct.
780 */
781#define list_for_each_entry(pos, head, member) \
782 for (pos = list_first_entry(head, typeof(*pos), member); \
783 !list_entry_is_head(pos, head, member); \
784 pos = list_next_entry(pos, member))
785
786/**
787 * list_for_each_entry_reverse - iterate backwards over list of given type.
788 * @pos: the type * to use as a loop cursor.
789 * @head: the head for your list.
790 * @member: the name of the list_head within the struct.
791 */
792#define list_for_each_entry_reverse(pos, head, member) \
793 for (pos = list_last_entry(head, typeof(*pos), member); \
794 !list_entry_is_head(pos, head, member); \
795 pos = list_prev_entry(pos, member))
796
797/**
798 * list_prepare_entry - prepare a pos entry for use in list_for_each_entry_continue()
799 * @pos: the type * to use as a start point
800 * @head: the head of the list
801 * @member: the name of the list_head within the struct.
802 *
803 * Prepares a pos entry for use as a start point in list_for_each_entry_continue().
804 */
805#define list_prepare_entry(pos, head, member) \
806 ((pos) ? : list_entry(head, typeof(*pos), member))
807
808/**
809 * list_for_each_entry_continue - continue iteration over list of given type
810 * @pos: the type * to use as a loop cursor.
811 * @head: the head for your list.
812 * @member: the name of the list_head within the struct.
813 *
814 * Continue to iterate over list of given type, continuing after
815 * the current position.
816 */
817#define list_for_each_entry_continue(pos, head, member) \
818 for (pos = list_next_entry(pos, member); \
819 !list_entry_is_head(pos, head, member); \
820 pos = list_next_entry(pos, member))
821
822/**
823 * list_for_each_entry_continue_reverse - iterate backwards from the given point
824 * @pos: the type * to use as a loop cursor.
825 * @head: the head for your list.
826 * @member: the name of the list_head within the struct.
827 *
828 * Start to iterate over list of given type backwards, continuing after
829 * the current position.
830 */
831#define list_for_each_entry_continue_reverse(pos, head, member) \
832 for (pos = list_prev_entry(pos, member); \
833 !list_entry_is_head(pos, head, member); \
834 pos = list_prev_entry(pos, member))
835
836/**
837 * list_for_each_entry_from - iterate over list of given type from the current point
838 * @pos: the type * to use as a loop cursor.
839 * @head: the head for your list.
840 * @member: the name of the list_head within the struct.
841 *
842 * Iterate over list of given type, continuing from current position.
843 */
844#define list_for_each_entry_from(pos, head, member) \
845 for (; !list_entry_is_head(pos, head, member); \
846 pos = list_next_entry(pos, member))
847
848/**
849 * list_for_each_entry_from_reverse - iterate backwards over list of given type
850 * from the current point
851 * @pos: the type * to use as a loop cursor.
852 * @head: the head for your list.
853 * @member: the name of the list_head within the struct.
854 *
855 * Iterate backwards over list of given type, continuing from current position.
856 */
857#define list_for_each_entry_from_reverse(pos, head, member) \
858 for (; !list_entry_is_head(pos, head, member); \
859 pos = list_prev_entry(pos, member))
860
861/**
862 * list_for_each_entry_safe - iterate over list of given type safe against removal of list entry
863 * @pos: the type * to use as a loop cursor.
864 * @n: another type * to use as temporary storage
865 * @head: the head for your list.
866 * @member: the name of the list_head within the struct.
867 */
868#define list_for_each_entry_safe(pos, n, head, member) \
869 for (pos = list_first_entry(head, typeof(*pos), member), \
870 n = list_next_entry(pos, member); \
871 !list_entry_is_head(pos, head, member); \
872 pos = n, n = list_next_entry(n, member))
873
874/**
875 * list_for_each_entry_safe_continue - continue list iteration safe against removal
876 * @pos: the type * to use as a loop cursor.
877 * @n: another type * to use as temporary storage
878 * @head: the head for your list.
879 * @member: the name of the list_head within the struct.
880 *
881 * Iterate over list of given type, continuing after current point,
882 * safe against removal of list entry.
883 */
884#define list_for_each_entry_safe_continue(pos, n, head, member) \
885 for (pos = list_next_entry(pos, member), \
886 n = list_next_entry(pos, member); \
887 !list_entry_is_head(pos, head, member); \
888 pos = n, n = list_next_entry(n, member))
889
890/**
891 * list_for_each_entry_safe_from - iterate over list from current point safe against removal
892 * @pos: the type * to use as a loop cursor.
893 * @n: another type * to use as temporary storage
894 * @head: the head for your list.
895 * @member: the name of the list_head within the struct.
896 *
897 * Iterate over list of given type from current point, safe against
898 * removal of list entry.
899 */
900#define list_for_each_entry_safe_from(pos, n, head, member) \
901 for (n = list_next_entry(pos, member); \
902 !list_entry_is_head(pos, head, member); \
903 pos = n, n = list_next_entry(n, member))
904
905/**
906 * list_for_each_entry_safe_reverse - iterate backwards over list safe against removal
907 * @pos: the type * to use as a loop cursor.
908 * @n: another type * to use as temporary storage
909 * @head: the head for your list.
910 * @member: the name of the list_head within the struct.
911 *
912 * Iterate backwards over list of given type, safe against removal
913 * of list entry.
914 */
915#define list_for_each_entry_safe_reverse(pos, n, head, member) \
916 for (pos = list_last_entry(head, typeof(*pos), member), \
917 n = list_prev_entry(pos, member); \
918 !list_entry_is_head(pos, head, member); \
919 pos = n, n = list_prev_entry(n, member))
920
921/**
922 * list_safe_reset_next - reset a stale list_for_each_entry_safe loop
923 * @pos: the loop cursor used in the list_for_each_entry_safe loop
924 * @n: temporary storage used in list_for_each_entry_safe
925 * @member: the name of the list_head within the struct.
926 *
927 * list_safe_reset_next is not safe to use in general if the list may be
928 * modified concurrently (eg. the lock is dropped in the loop body). An
929 * exception to this is if the cursor element (pos) is pinned in the list,
930 * and list_safe_reset_next is called after re-taking the lock and before
931 * completing the current iteration of the loop body.
932 */
933#define list_safe_reset_next(pos, n, member) \
934 n = list_next_entry(pos, member)
935
936/*
937 * Double linked lists with a single pointer list head.
938 * Mostly useful for hash tables where the two pointer list head is
939 * too wasteful.
940 * You lose the ability to access the tail in O(1).
941 */
942
943#define HLIST_HEAD_INIT { .first = NULL }
944#define HLIST_HEAD(name) struct hlist_head name = { .first = NULL }
945#define INIT_HLIST_HEAD(ptr) ((ptr)->first = NULL)
946static inline void INIT_HLIST_NODE(struct hlist_node *h)
947{
948 h->next = NULL;
949 h->pprev = NULL;
950}
951
952/**
953 * hlist_unhashed - Has node been removed from list and reinitialized?
954 * @h: Node to be checked
955 *
956 * Not that not all removal functions will leave a node in unhashed
957 * state. For example, hlist_nulls_del_init_rcu() does leave the
958 * node in unhashed state, but hlist_nulls_del() does not.
959 */
960static inline int hlist_unhashed(const struct hlist_node *h)
961{
962 return !h->pprev;
963}
964
965/**
966 * hlist_unhashed_lockless - Version of hlist_unhashed for lockless use
967 * @h: Node to be checked
968 *
969 * This variant of hlist_unhashed() must be used in lockless contexts
970 * to avoid potential load-tearing. The READ_ONCE() is paired with the
971 * various WRITE_ONCE() in hlist helpers that are defined below.
972 */
973static inline int hlist_unhashed_lockless(const struct hlist_node *h)
974{
975 return !READ_ONCE(h->pprev);
976}
977
978/**
979 * hlist_empty - Is the specified hlist_head structure an empty hlist?
980 * @h: Structure to check.
981 */
982static inline int hlist_empty(const struct hlist_head *h)
983{
984 return !READ_ONCE(h->first);
985}
986
987static inline void __hlist_del(struct hlist_node *n)
988{
989 struct hlist_node *next = n->next;
990 struct hlist_node **pprev = n->pprev;
991
992 WRITE_ONCE(*pprev, next);
993 if (next)
994 WRITE_ONCE(next->pprev, pprev);
995}
996
997/**
998 * hlist_del - Delete the specified hlist_node from its list
999 * @n: Node to delete.
1000 *
1001 * Note that this function leaves the node in hashed state. Use
1002 * hlist_del_init() or similar instead to unhash @n.
1003 */
1004static inline void hlist_del(struct hlist_node *n)
1005{
1006 __hlist_del(n);
1007 n->next = LIST_POISON1;
1008 n->pprev = LIST_POISON2;
1009}
1010
1011/**
1012 * hlist_del_init - Delete the specified hlist_node from its list and initialize
1013 * @n: Node to delete.
1014 *
1015 * Note that this function leaves the node in unhashed state.
1016 */
1017static inline void hlist_del_init(struct hlist_node *n)
1018{
1019 if (!hlist_unhashed(h: n)) {
1020 __hlist_del(n);
1021 INIT_HLIST_NODE(h: n);
1022 }
1023}
1024
1025/**
1026 * hlist_add_head - add a new entry at the beginning of the hlist
1027 * @n: new entry to be added
1028 * @h: hlist head to add it after
1029 *
1030 * Insert a new entry after the specified head.
1031 * This is good for implementing stacks.
1032 */
1033static inline void hlist_add_head(struct hlist_node *n, struct hlist_head *h)
1034{
1035 struct hlist_node *first = h->first;
1036 WRITE_ONCE(n->next, first);
1037 if (first)
1038 WRITE_ONCE(first->pprev, &n->next);
1039 WRITE_ONCE(h->first, n);
1040 WRITE_ONCE(n->pprev, &h->first);
1041}
1042
1043/**
1044 * hlist_add_before - add a new entry before the one specified
1045 * @n: new entry to be added
1046 * @next: hlist node to add it before, which must be non-NULL
1047 */
1048static inline void hlist_add_before(struct hlist_node *n,
1049 struct hlist_node *next)
1050{
1051 WRITE_ONCE(n->pprev, next->pprev);
1052 WRITE_ONCE(n->next, next);
1053 WRITE_ONCE(next->pprev, &n->next);
1054 WRITE_ONCE(*(n->pprev), n);
1055}
1056
1057/**
1058 * hlist_add_behind - add a new entry after the one specified
1059 * @n: new entry to be added
1060 * @prev: hlist node to add it after, which must be non-NULL
1061 */
1062static inline void hlist_add_behind(struct hlist_node *n,
1063 struct hlist_node *prev)
1064{
1065 WRITE_ONCE(n->next, prev->next);
1066 WRITE_ONCE(prev->next, n);
1067 WRITE_ONCE(n->pprev, &prev->next);
1068
1069 if (n->next)
1070 WRITE_ONCE(n->next->pprev, &n->next);
1071}
1072
1073/**
1074 * hlist_add_fake - create a fake hlist consisting of a single headless node
1075 * @n: Node to make a fake list out of
1076 *
1077 * This makes @n appear to be its own predecessor on a headless hlist.
1078 * The point of this is to allow things like hlist_del() to work correctly
1079 * in cases where there is no list.
1080 */
1081static inline void hlist_add_fake(struct hlist_node *n)
1082{
1083 n->pprev = &n->next;
1084}
1085
1086/**
1087 * hlist_fake: Is this node a fake hlist?
1088 * @h: Node to check for being a self-referential fake hlist.
1089 */
1090static inline bool hlist_fake(struct hlist_node *h)
1091{
1092 return h->pprev == &h->next;
1093}
1094
1095/**
1096 * hlist_is_singular_node - is node the only element of the specified hlist?
1097 * @n: Node to check for singularity.
1098 * @h: Header for potentially singular list.
1099 *
1100 * Check whether the node is the only node of the head without
1101 * accessing head, thus avoiding unnecessary cache misses.
1102 */
1103static inline bool
1104hlist_is_singular_node(struct hlist_node *n, struct hlist_head *h)
1105{
1106 return !n->next && n->pprev == &h->first;
1107}
1108
1109/**
1110 * hlist_move_list - Move an hlist
1111 * @old: hlist_head for old list.
1112 * @new: hlist_head for new list.
1113 *
1114 * Move a list from one list head to another. Fixup the pprev
1115 * reference of the first entry if it exists.
1116 */
1117static inline void hlist_move_list(struct hlist_head *old,
1118 struct hlist_head *new)
1119{
1120 new->first = old->first;
1121 if (new->first)
1122 new->first->pprev = &new->first;
1123 old->first = NULL;
1124}
1125
1126/**
1127 * hlist_splice_init() - move all entries from one list to another
1128 * @from: hlist_head from which entries will be moved
1129 * @last: last entry on the @from list
1130 * @to: hlist_head to which entries will be moved
1131 *
1132 * @to can be empty, @from must contain at least @last.
1133 */
1134static inline void hlist_splice_init(struct hlist_head *from,
1135 struct hlist_node *last,
1136 struct hlist_head *to)
1137{
1138 if (to->first)
1139 to->first->pprev = &last->next;
1140 last->next = to->first;
1141 to->first = from->first;
1142 from->first->pprev = &to->first;
1143 from->first = NULL;
1144}
1145
1146#define hlist_entry(ptr, type, member) container_of(ptr,type,member)
1147
1148#define hlist_for_each(pos, head) \
1149 for (pos = (head)->first; pos ; pos = pos->next)
1150
1151#define hlist_for_each_safe(pos, n, head) \
1152 for (pos = (head)->first; pos && ({ n = pos->next; 1; }); \
1153 pos = n)
1154
1155#define hlist_entry_safe(ptr, type, member) \
1156 ({ typeof(ptr) ____ptr = (ptr); \
1157 ____ptr ? hlist_entry(____ptr, type, member) : NULL; \
1158 })
1159
1160/**
1161 * hlist_for_each_entry - iterate over list of given type
1162 * @pos: the type * to use as a loop cursor.
1163 * @head: the head for your list.
1164 * @member: the name of the hlist_node within the struct.
1165 */
1166#define hlist_for_each_entry(pos, head, member) \
1167 for (pos = hlist_entry_safe((head)->first, typeof(*(pos)), member);\
1168 pos; \
1169 pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member))
1170
1171/**
1172 * hlist_for_each_entry_continue - iterate over a hlist continuing after current point
1173 * @pos: the type * to use as a loop cursor.
1174 * @member: the name of the hlist_node within the struct.
1175 */
1176#define hlist_for_each_entry_continue(pos, member) \
1177 for (pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member);\
1178 pos; \
1179 pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member))
1180
1181/**
1182 * hlist_for_each_entry_from - iterate over a hlist continuing from current point
1183 * @pos: the type * to use as a loop cursor.
1184 * @member: the name of the hlist_node within the struct.
1185 */
1186#define hlist_for_each_entry_from(pos, member) \
1187 for (; pos; \
1188 pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member))
1189
1190/**
1191 * hlist_for_each_entry_safe - iterate over list of given type safe against removal of list entry
1192 * @pos: the type * to use as a loop cursor.
1193 * @n: a &struct hlist_node to use as temporary storage
1194 * @head: the head for your list.
1195 * @member: the name of the hlist_node within the struct.
1196 */
1197#define hlist_for_each_entry_safe(pos, n, head, member) \
1198 for (pos = hlist_entry_safe((head)->first, typeof(*pos), member);\
1199 pos && ({ n = pos->member.next; 1; }); \
1200 pos = hlist_entry_safe(n, typeof(*pos), member))
1201
1202/**
1203 * hlist_count_nodes - count nodes in the hlist
1204 * @head: the head for your hlist.
1205 */
1206static inline size_t hlist_count_nodes(struct hlist_head *head)
1207{
1208 struct hlist_node *pos;
1209 size_t count = 0;
1210
1211 hlist_for_each(pos, head)
1212 count++;
1213
1214 return count;
1215}
1216
1217#endif
1218