1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Copyright (c) 2013 Red Hat, Inc. and Parallels Inc. All rights reserved.
4 * Authors: David Chinner and Glauber Costa
5 *
6 * Generic LRU infrastructure
7 */
8#include <linux/kernel.h>
9#include <linux/module.h>
10#include <linux/mm.h>
11#include <linux/list_lru.h>
12#include <linux/slab.h>
13#include <linux/mutex.h>
14#include <linux/memcontrol.h>
15#include "slab.h"
16#include "internal.h"
17
18#ifdef CONFIG_MEMCG_KMEM
19static LIST_HEAD(memcg_list_lrus);
20static DEFINE_MUTEX(list_lrus_mutex);
21
22static inline bool list_lru_memcg_aware(struct list_lru *lru)
23{
24 return lru->memcg_aware;
25}
26
27static void list_lru_register(struct list_lru *lru)
28{
29 if (!list_lru_memcg_aware(lru))
30 return;
31
32 mutex_lock(&list_lrus_mutex);
33 list_add(&lru->list, &memcg_list_lrus);
34 mutex_unlock(&list_lrus_mutex);
35}
36
37static void list_lru_unregister(struct list_lru *lru)
38{
39 if (!list_lru_memcg_aware(lru))
40 return;
41
42 mutex_lock(&list_lrus_mutex);
43 list_del(&lru->list);
44 mutex_unlock(&list_lrus_mutex);
45}
46
47static int lru_shrinker_id(struct list_lru *lru)
48{
49 return lru->shrinker_id;
50}
51
52static inline struct list_lru_one *
53list_lru_from_memcg_idx(struct list_lru *lru, int nid, int idx)
54{
55 if (list_lru_memcg_aware(lru) && idx >= 0) {
56 struct list_lru_memcg *mlru = xa_load(&lru->xa, idx);
57
58 return mlru ? &mlru->node[nid] : NULL;
59 }
60 return &lru->node[nid].lru;
61}
62
63static inline struct list_lru_one *
64list_lru_from_kmem(struct list_lru *lru, int nid, void *ptr,
65 struct mem_cgroup **memcg_ptr)
66{
67 struct list_lru_node *nlru = &lru->node[nid];
68 struct list_lru_one *l = &nlru->lru;
69 struct mem_cgroup *memcg = NULL;
70
71 if (!list_lru_memcg_aware(lru))
72 goto out;
73
74 memcg = mem_cgroup_from_slab_obj(ptr);
75 if (!memcg)
76 goto out;
77
78 l = list_lru_from_memcg_idx(lru, nid, memcg_kmem_id(memcg));
79out:
80 if (memcg_ptr)
81 *memcg_ptr = memcg;
82 return l;
83}
84#else
85static void list_lru_register(struct list_lru *lru)
86{
87}
88
89static void list_lru_unregister(struct list_lru *lru)
90{
91}
92
93static int lru_shrinker_id(struct list_lru *lru)
94{
95 return -1;
96}
97
98static inline bool list_lru_memcg_aware(struct list_lru *lru)
99{
100 return false;
101}
102
103static inline struct list_lru_one *
104list_lru_from_memcg_idx(struct list_lru *lru, int nid, int idx)
105{
106 return &lru->node[nid].lru;
107}
108
109static inline struct list_lru_one *
110list_lru_from_kmem(struct list_lru *lru, int nid, void *ptr,
111 struct mem_cgroup **memcg_ptr)
112{
113 if (memcg_ptr)
114 *memcg_ptr = NULL;
115 return &lru->node[nid].lru;
116}
117#endif /* CONFIG_MEMCG_KMEM */
118
119bool list_lru_add(struct list_lru *lru, struct list_head *item)
120{
121 int nid = page_to_nid(virt_to_page(item));
122 struct list_lru_node *nlru = &lru->node[nid];
123 struct mem_cgroup *memcg;
124 struct list_lru_one *l;
125
126 spin_lock(lock: &nlru->lock);
127 if (list_empty(head: item)) {
128 l = list_lru_from_kmem(lru, nid, ptr: item, memcg_ptr: &memcg);
129 list_add_tail(new: item, head: &l->list);
130 /* Set shrinker bit if the first element was added */
131 if (!l->nr_items++)
132 set_shrinker_bit(memcg, nid,
133 shrinker_id: lru_shrinker_id(lru));
134 nlru->nr_items++;
135 spin_unlock(lock: &nlru->lock);
136 return true;
137 }
138 spin_unlock(lock: &nlru->lock);
139 return false;
140}
141EXPORT_SYMBOL_GPL(list_lru_add);
142
143bool list_lru_del(struct list_lru *lru, struct list_head *item)
144{
145 int nid = page_to_nid(virt_to_page(item));
146 struct list_lru_node *nlru = &lru->node[nid];
147 struct list_lru_one *l;
148
149 spin_lock(lock: &nlru->lock);
150 if (!list_empty(head: item)) {
151 l = list_lru_from_kmem(lru, nid, ptr: item, NULL);
152 list_del_init(entry: item);
153 l->nr_items--;
154 nlru->nr_items--;
155 spin_unlock(lock: &nlru->lock);
156 return true;
157 }
158 spin_unlock(lock: &nlru->lock);
159 return false;
160}
161EXPORT_SYMBOL_GPL(list_lru_del);
162
163void list_lru_isolate(struct list_lru_one *list, struct list_head *item)
164{
165 list_del_init(entry: item);
166 list->nr_items--;
167}
168EXPORT_SYMBOL_GPL(list_lru_isolate);
169
170void list_lru_isolate_move(struct list_lru_one *list, struct list_head *item,
171 struct list_head *head)
172{
173 list_move(list: item, head);
174 list->nr_items--;
175}
176EXPORT_SYMBOL_GPL(list_lru_isolate_move);
177
178unsigned long list_lru_count_one(struct list_lru *lru,
179 int nid, struct mem_cgroup *memcg)
180{
181 struct list_lru_one *l;
182 long count;
183
184 rcu_read_lock();
185 l = list_lru_from_memcg_idx(lru, nid, idx: memcg_kmem_id(memcg));
186 count = l ? READ_ONCE(l->nr_items) : 0;
187 rcu_read_unlock();
188
189 if (unlikely(count < 0))
190 count = 0;
191
192 return count;
193}
194EXPORT_SYMBOL_GPL(list_lru_count_one);
195
196unsigned long list_lru_count_node(struct list_lru *lru, int nid)
197{
198 struct list_lru_node *nlru;
199
200 nlru = &lru->node[nid];
201 return nlru->nr_items;
202}
203EXPORT_SYMBOL_GPL(list_lru_count_node);
204
205static unsigned long
206__list_lru_walk_one(struct list_lru *lru, int nid, int memcg_idx,
207 list_lru_walk_cb isolate, void *cb_arg,
208 unsigned long *nr_to_walk)
209{
210 struct list_lru_node *nlru = &lru->node[nid];
211 struct list_lru_one *l;
212 struct list_head *item, *n;
213 unsigned long isolated = 0;
214
215restart:
216 l = list_lru_from_memcg_idx(lru, nid, idx: memcg_idx);
217 if (!l)
218 goto out;
219
220 list_for_each_safe(item, n, &l->list) {
221 enum lru_status ret;
222
223 /*
224 * decrement nr_to_walk first so that we don't livelock if we
225 * get stuck on large numbers of LRU_RETRY items
226 */
227 if (!*nr_to_walk)
228 break;
229 --*nr_to_walk;
230
231 ret = isolate(item, l, &nlru->lock, cb_arg);
232 switch (ret) {
233 case LRU_REMOVED_RETRY:
234 assert_spin_locked(&nlru->lock);
235 fallthrough;
236 case LRU_REMOVED:
237 isolated++;
238 nlru->nr_items--;
239 /*
240 * If the lru lock has been dropped, our list
241 * traversal is now invalid and so we have to
242 * restart from scratch.
243 */
244 if (ret == LRU_REMOVED_RETRY)
245 goto restart;
246 break;
247 case LRU_ROTATE:
248 list_move_tail(list: item, head: &l->list);
249 break;
250 case LRU_SKIP:
251 break;
252 case LRU_RETRY:
253 /*
254 * The lru lock has been dropped, our list traversal is
255 * now invalid and so we have to restart from scratch.
256 */
257 assert_spin_locked(&nlru->lock);
258 goto restart;
259 default:
260 BUG();
261 }
262 }
263out:
264 return isolated;
265}
266
267unsigned long
268list_lru_walk_one(struct list_lru *lru, int nid, struct mem_cgroup *memcg,
269 list_lru_walk_cb isolate, void *cb_arg,
270 unsigned long *nr_to_walk)
271{
272 struct list_lru_node *nlru = &lru->node[nid];
273 unsigned long ret;
274
275 spin_lock(lock: &nlru->lock);
276 ret = __list_lru_walk_one(lru, nid, memcg_idx: memcg_kmem_id(memcg), isolate,
277 cb_arg, nr_to_walk);
278 spin_unlock(lock: &nlru->lock);
279 return ret;
280}
281EXPORT_SYMBOL_GPL(list_lru_walk_one);
282
283unsigned long
284list_lru_walk_one_irq(struct list_lru *lru, int nid, struct mem_cgroup *memcg,
285 list_lru_walk_cb isolate, void *cb_arg,
286 unsigned long *nr_to_walk)
287{
288 struct list_lru_node *nlru = &lru->node[nid];
289 unsigned long ret;
290
291 spin_lock_irq(lock: &nlru->lock);
292 ret = __list_lru_walk_one(lru, nid, memcg_idx: memcg_kmem_id(memcg), isolate,
293 cb_arg, nr_to_walk);
294 spin_unlock_irq(lock: &nlru->lock);
295 return ret;
296}
297
298unsigned long list_lru_walk_node(struct list_lru *lru, int nid,
299 list_lru_walk_cb isolate, void *cb_arg,
300 unsigned long *nr_to_walk)
301{
302 long isolated = 0;
303
304 isolated += list_lru_walk_one(lru, nid, NULL, isolate, cb_arg,
305 nr_to_walk);
306
307#ifdef CONFIG_MEMCG_KMEM
308 if (*nr_to_walk > 0 && list_lru_memcg_aware(lru)) {
309 struct list_lru_memcg *mlru;
310 unsigned long index;
311
312 xa_for_each(&lru->xa, index, mlru) {
313 struct list_lru_node *nlru = &lru->node[nid];
314
315 spin_lock(&nlru->lock);
316 isolated += __list_lru_walk_one(lru, nid, index,
317 isolate, cb_arg,
318 nr_to_walk);
319 spin_unlock(&nlru->lock);
320
321 if (*nr_to_walk <= 0)
322 break;
323 }
324 }
325#endif
326
327 return isolated;
328}
329EXPORT_SYMBOL_GPL(list_lru_walk_node);
330
331static void init_one_lru(struct list_lru_one *l)
332{
333 INIT_LIST_HEAD(list: &l->list);
334 l->nr_items = 0;
335}
336
337#ifdef CONFIG_MEMCG_KMEM
338static struct list_lru_memcg *memcg_init_list_lru_one(gfp_t gfp)
339{
340 int nid;
341 struct list_lru_memcg *mlru;
342
343 mlru = kmalloc(struct_size(mlru, node, nr_node_ids), gfp);
344 if (!mlru)
345 return NULL;
346
347 for_each_node(nid)
348 init_one_lru(&mlru->node[nid]);
349
350 return mlru;
351}
352
353static void memcg_list_lru_free(struct list_lru *lru, int src_idx)
354{
355 struct list_lru_memcg *mlru = xa_erase_irq(&lru->xa, src_idx);
356
357 /*
358 * The __list_lru_walk_one() can walk the list of this node.
359 * We need kvfree_rcu() here. And the walking of the list
360 * is under lru->node[nid]->lock, which can serve as a RCU
361 * read-side critical section.
362 */
363 if (mlru)
364 kvfree_rcu(mlru, rcu);
365}
366
367static inline void memcg_init_list_lru(struct list_lru *lru, bool memcg_aware)
368{
369 if (memcg_aware)
370 xa_init_flags(&lru->xa, XA_FLAGS_LOCK_IRQ);
371 lru->memcg_aware = memcg_aware;
372}
373
374static void memcg_destroy_list_lru(struct list_lru *lru)
375{
376 XA_STATE(xas, &lru->xa, 0);
377 struct list_lru_memcg *mlru;
378
379 if (!list_lru_memcg_aware(lru))
380 return;
381
382 xas_lock_irq(&xas);
383 xas_for_each(&xas, mlru, ULONG_MAX) {
384 kfree(mlru);
385 xas_store(&xas, NULL);
386 }
387 xas_unlock_irq(&xas);
388}
389
390static void memcg_reparent_list_lru_node(struct list_lru *lru, int nid,
391 int src_idx, struct mem_cgroup *dst_memcg)
392{
393 struct list_lru_node *nlru = &lru->node[nid];
394 int dst_idx = dst_memcg->kmemcg_id;
395 struct list_lru_one *src, *dst;
396
397 /*
398 * Since list_lru_{add,del} may be called under an IRQ-safe lock,
399 * we have to use IRQ-safe primitives here to avoid deadlock.
400 */
401 spin_lock_irq(&nlru->lock);
402
403 src = list_lru_from_memcg_idx(lru, nid, src_idx);
404 if (!src)
405 goto out;
406 dst = list_lru_from_memcg_idx(lru, nid, dst_idx);
407
408 list_splice_init(&src->list, &dst->list);
409
410 if (src->nr_items) {
411 dst->nr_items += src->nr_items;
412 set_shrinker_bit(dst_memcg, nid, lru_shrinker_id(lru));
413 src->nr_items = 0;
414 }
415out:
416 spin_unlock_irq(&nlru->lock);
417}
418
419static void memcg_reparent_list_lru(struct list_lru *lru,
420 int src_idx, struct mem_cgroup *dst_memcg)
421{
422 int i;
423
424 for_each_node(i)
425 memcg_reparent_list_lru_node(lru, i, src_idx, dst_memcg);
426
427 memcg_list_lru_free(lru, src_idx);
428}
429
430void memcg_reparent_list_lrus(struct mem_cgroup *memcg, struct mem_cgroup *parent)
431{
432 struct cgroup_subsys_state *css;
433 struct list_lru *lru;
434 int src_idx = memcg->kmemcg_id;
435
436 /*
437 * Change kmemcg_id of this cgroup and all its descendants to the
438 * parent's id, and then move all entries from this cgroup's list_lrus
439 * to ones of the parent.
440 *
441 * After we have finished, all list_lrus corresponding to this cgroup
442 * are guaranteed to remain empty. So we can safely free this cgroup's
443 * list lrus in memcg_list_lru_free().
444 *
445 * Changing ->kmemcg_id to the parent can prevent memcg_list_lru_alloc()
446 * from allocating list lrus for this cgroup after memcg_list_lru_free()
447 * call.
448 */
449 rcu_read_lock();
450 css_for_each_descendant_pre(css, &memcg->css) {
451 struct mem_cgroup *child;
452
453 child = mem_cgroup_from_css(css);
454 WRITE_ONCE(child->kmemcg_id, parent->kmemcg_id);
455 }
456 rcu_read_unlock();
457
458 mutex_lock(&list_lrus_mutex);
459 list_for_each_entry(lru, &memcg_list_lrus, list)
460 memcg_reparent_list_lru(lru, src_idx, parent);
461 mutex_unlock(&list_lrus_mutex);
462}
463
464static inline bool memcg_list_lru_allocated(struct mem_cgroup *memcg,
465 struct list_lru *lru)
466{
467 int idx = memcg->kmemcg_id;
468
469 return idx < 0 || xa_load(&lru->xa, idx);
470}
471
472int memcg_list_lru_alloc(struct mem_cgroup *memcg, struct list_lru *lru,
473 gfp_t gfp)
474{
475 int i;
476 unsigned long flags;
477 struct list_lru_memcg_table {
478 struct list_lru_memcg *mlru;
479 struct mem_cgroup *memcg;
480 } *table;
481 XA_STATE(xas, &lru->xa, 0);
482
483 if (!list_lru_memcg_aware(lru) || memcg_list_lru_allocated(memcg, lru))
484 return 0;
485
486 gfp &= GFP_RECLAIM_MASK;
487 table = kmalloc_array(memcg->css.cgroup->level, sizeof(*table), gfp);
488 if (!table)
489 return -ENOMEM;
490
491 /*
492 * Because the list_lru can be reparented to the parent cgroup's
493 * list_lru, we should make sure that this cgroup and all its
494 * ancestors have allocated list_lru_memcg.
495 */
496 for (i = 0; memcg; memcg = parent_mem_cgroup(memcg), i++) {
497 if (memcg_list_lru_allocated(memcg, lru))
498 break;
499
500 table[i].memcg = memcg;
501 table[i].mlru = memcg_init_list_lru_one(gfp);
502 if (!table[i].mlru) {
503 while (i--)
504 kfree(table[i].mlru);
505 kfree(table);
506 return -ENOMEM;
507 }
508 }
509
510 xas_lock_irqsave(&xas, flags);
511 while (i--) {
512 int index = READ_ONCE(table[i].memcg->kmemcg_id);
513 struct list_lru_memcg *mlru = table[i].mlru;
514
515 xas_set(&xas, index);
516retry:
517 if (unlikely(index < 0 || xas_error(&xas) || xas_load(&xas))) {
518 kfree(mlru);
519 } else {
520 xas_store(&xas, mlru);
521 if (xas_error(&xas) == -ENOMEM) {
522 xas_unlock_irqrestore(&xas, flags);
523 if (xas_nomem(&xas, gfp))
524 xas_set_err(&xas, 0);
525 xas_lock_irqsave(&xas, flags);
526 /*
527 * The xas lock has been released, this memcg
528 * can be reparented before us. So reload
529 * memcg id. More details see the comments
530 * in memcg_reparent_list_lrus().
531 */
532 index = READ_ONCE(table[i].memcg->kmemcg_id);
533 if (index < 0)
534 xas_set_err(&xas, 0);
535 else if (!xas_error(&xas) && index != xas.xa_index)
536 xas_set(&xas, index);
537 goto retry;
538 }
539 }
540 }
541 /* xas_nomem() is used to free memory instead of memory allocation. */
542 if (xas.xa_alloc)
543 xas_nomem(&xas, gfp);
544 xas_unlock_irqrestore(&xas, flags);
545 kfree(table);
546
547 return xas_error(&xas);
548}
549#else
550static inline void memcg_init_list_lru(struct list_lru *lru, bool memcg_aware)
551{
552}
553
554static void memcg_destroy_list_lru(struct list_lru *lru)
555{
556}
557#endif /* CONFIG_MEMCG_KMEM */
558
559int __list_lru_init(struct list_lru *lru, bool memcg_aware,
560 struct lock_class_key *key, struct shrinker *shrinker)
561{
562 int i;
563
564#ifdef CONFIG_MEMCG_KMEM
565 if (shrinker)
566 lru->shrinker_id = shrinker->id;
567 else
568 lru->shrinker_id = -1;
569#endif
570
571 lru->node = kcalloc(nr_node_ids, size: sizeof(*lru->node), GFP_KERNEL);
572 if (!lru->node)
573 return -ENOMEM;
574
575 for_each_node(i) {
576 spin_lock_init(&lru->node[i].lock);
577 if (key)
578 lockdep_set_class(&lru->node[i].lock, key);
579 init_one_lru(l: &lru->node[i].lru);
580 }
581
582 memcg_init_list_lru(lru, memcg_aware);
583 list_lru_register(lru);
584
585 return 0;
586}
587EXPORT_SYMBOL_GPL(__list_lru_init);
588
589void list_lru_destroy(struct list_lru *lru)
590{
591 /* Already destroyed or not yet initialized? */
592 if (!lru->node)
593 return;
594
595 list_lru_unregister(lru);
596
597 memcg_destroy_list_lru(lru);
598 kfree(objp: lru->node);
599 lru->node = NULL;
600
601#ifdef CONFIG_MEMCG_KMEM
602 lru->shrinker_id = -1;
603#endif
604}
605EXPORT_SYMBOL_GPL(list_lru_destroy);
606

source code of linux/mm/list_lru.c