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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
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 *
64lock_list_lru_of_memcg(struct list_lru *lru, int nid, struct mem_cgroup *memcg,
65 bool irq, bool skip_empty)
66{
67 struct list_lru_one *l;
68 long nr_items;
69
70 rcu_read_lock();
71again:
72 l = list_lru_from_memcg_idx(lru, nid, memcg_kmem_id(memcg));
73 if (likely(l)) {
74 if (irq)
75 spin_lock_irq(&l->lock);
76 else
77 spin_lock(&l->lock);
78 nr_items = READ_ONCE(l->nr_items);
79 if (likely(nr_items != LONG_MIN)) {
80 rcu_read_unlock();
81 return l;
82 }
83 if (irq)
84 spin_unlock_irq(&l->lock);
85 else
86 spin_unlock(&l->lock);
87 }
88 /*
89 * Caller may simply bail out if raced with reparenting or
90 * may iterate through the list_lru and expect empty slots.
91 */
92 if (skip_empty) {
93 rcu_read_unlock();
94 return NULL;
95 }
96 VM_WARN_ON(!css_is_dying(&memcg->css));
97 memcg = parent_mem_cgroup(memcg);
98 goto again;
99}
100
101static inline void unlock_list_lru(struct list_lru_one *l, bool irq_off)
102{
103 if (irq_off)
104 spin_unlock_irq(&l->lock);
105 else
106 spin_unlock(&l->lock);
107}
108#else
109static void list_lru_register(struct list_lru *lru)
110{
111}
112
113static void list_lru_unregister(struct list_lru *lru)
114{
115}
116
117static int lru_shrinker_id(struct list_lru *lru)
118{
119 return -1;
120}
121
122static inline bool list_lru_memcg_aware(struct list_lru *lru)
123{
124 return false;
125}
126
127static inline struct list_lru_one *
128list_lru_from_memcg_idx(struct list_lru *lru, int nid, int idx)
129{
130 return &lru->node[nid].lru;
131}
132
133static inline struct list_lru_one *
134lock_list_lru_of_memcg(struct list_lru *lru, int nid, struct mem_cgroup *memcg,
135 bool irq, bool skip_empty)
136{
137 struct list_lru_one *l = &lru->node[nid].lru;
138
139 if (irq)
140 spin_lock_irq(&l->lock);
141 else
142 spin_lock(&l->lock);
143
144 return l;
145}
146
147static inline void unlock_list_lru(struct list_lru_one *l, bool irq_off)
148{
149 if (irq_off)
150 spin_unlock_irq(&l->lock);
151 else
152 spin_unlock(&l->lock);
153}
154#endif /* CONFIG_MEMCG */
155
156/* The caller must ensure the memcg lifetime. */
157bool list_lru_add(struct list_lru *lru, struct list_head *item, int nid,
158 struct mem_cgroup *memcg)
159{
160 struct list_lru_node *nlru = &lru->node[nid];
161 struct list_lru_one *l;
162
163 l = lock_list_lru_of_memcg(lru, nid, memcg, false, false);
164 if (!l)
165 return false;
166 if (list_empty(item)) {
167 list_add_tail(item, &l->list);
168 /* Set shrinker bit if the first element was added */
169 if (!l->nr_items++)
170 set_shrinker_bit(memcg, nid, lru_shrinker_id(lru));
171 unlock_list_lru(l, false);
172 atomic_long_inc(&nlru->nr_items);
173 return true;
174 }
175 unlock_list_lru(l, false);
176 return false;
177}
178
179bool list_lru_add_obj(struct list_lru *lru, struct list_head *item)
180{
181 bool ret;
182 int nid = page_to_nid(virt_to_page(item));
183
184 if (list_lru_memcg_aware(lru)) {
185 rcu_read_lock();
186 ret = list_lru_add(lru, item, nid, mem_cgroup_from_slab_obj(item));
187 rcu_read_unlock();
188 } else {
189 ret = list_lru_add(lru, item, nid, NULL);
190 }
191
192 return ret;
193}
194EXPORT_SYMBOL_GPL(list_lru_add_obj);
195
196/* The caller must ensure the memcg lifetime. */
197bool list_lru_del(struct list_lru *lru, struct list_head *item, int nid,
198 struct mem_cgroup *memcg)
199{
200 struct list_lru_node *nlru = &lru->node[nid];
201 struct list_lru_one *l;
202 l = lock_list_lru_of_memcg(lru, nid, memcg, false, false);
203 if (!l)
204 return false;
205 if (!list_empty(item)) {
206 list_del_init(item);
207 l->nr_items--;
208 unlock_list_lru(l, false);
209 atomic_long_dec(&nlru->nr_items);
210 return true;
211 }
212 unlock_list_lru(l, false);
213 return false;
214}
215
216bool list_lru_del_obj(struct list_lru *lru, struct list_head *item)
217{
218 bool ret;
219 int nid = page_to_nid(virt_to_page(item));
220
221 if (list_lru_memcg_aware(lru)) {
222 rcu_read_lock();
223 ret = list_lru_del(lru, item, nid, mem_cgroup_from_slab_obj(item));
224 rcu_read_unlock();
225 } else {
226 ret = list_lru_del(lru, item, nid, NULL);
227 }
228
229 return ret;
230}
231EXPORT_SYMBOL_GPL(list_lru_del_obj);
232
233void list_lru_isolate(struct list_lru_one *list, struct list_head *item)
234{
235 list_del_init(item);
236 list->nr_items--;
237}
238EXPORT_SYMBOL_GPL(list_lru_isolate);
239
240void list_lru_isolate_move(struct list_lru_one *list, struct list_head *item,
241 struct list_head *head)
242{
243 list_move(item, head);
244 list->nr_items--;
245}
246EXPORT_SYMBOL_GPL(list_lru_isolate_move);
247
248unsigned long list_lru_count_one(struct list_lru *lru,
249 int nid, struct mem_cgroup *memcg)
250{
251 struct list_lru_one *l;
252 long count;
253
254 rcu_read_lock();
255 l = list_lru_from_memcg_idx(lru, nid, memcg_kmem_id(memcg));
256 count = l ? READ_ONCE(l->nr_items) : 0;
257 rcu_read_unlock();
258
259 if (unlikely(count < 0))
260 count = 0;
261
262 return count;
263}
264EXPORT_SYMBOL_GPL(list_lru_count_one);
265
266unsigned long list_lru_count_node(struct list_lru *lru, int nid)
267{
268 struct list_lru_node *nlru;
269
270 nlru = &lru->node[nid];
271 return atomic_long_read(&nlru->nr_items);
272}
273EXPORT_SYMBOL_GPL(list_lru_count_node);
274
275static unsigned long
276__list_lru_walk_one(struct list_lru *lru, int nid, struct mem_cgroup *memcg,
277 list_lru_walk_cb isolate, void *cb_arg,
278 unsigned long *nr_to_walk, bool irq_off)
279{
280 struct list_lru_node *nlru = &lru->node[nid];
281 struct list_lru_one *l = NULL;
282 struct list_head *item, *n;
283 unsigned long isolated = 0;
284
285restart:
286 l = lock_list_lru_of_memcg(lru, nid, memcg, irq_off, true);
287 if (!l)
288 return isolated;
289 list_for_each_safe(item, n, &l->list) {
290 enum lru_status ret;
291
292 /*
293 * decrement nr_to_walk first so that we don't livelock if we
294 * get stuck on large numbers of LRU_RETRY items
295 */
296 if (!*nr_to_walk)
297 break;
298 --*nr_to_walk;
299
300 ret = isolate(item, l, cb_arg);
301 switch (ret) {
302 /*
303 * LRU_RETRY, LRU_REMOVED_RETRY and LRU_STOP will drop the lru
304 * lock. List traversal will have to restart from scratch.
305 */
306 case LRU_RETRY:
307 goto restart;
308 case LRU_REMOVED_RETRY:
309 fallthrough;
310 case LRU_REMOVED:
311 isolated++;
312 atomic_long_dec(&nlru->nr_items);
313 if (ret == LRU_REMOVED_RETRY)
314 goto restart;
315 break;
316 case LRU_ROTATE:
317 list_move_tail(item, &l->list);
318 break;
319 case LRU_SKIP:
320 break;
321 case LRU_STOP:
322 goto out;
323 default:
324 BUG();
325 }
326 }
327 unlock_list_lru(l, irq_off);
328out:
329 return isolated;
330}
331
332unsigned long
333list_lru_walk_one(struct list_lru *lru, int nid, struct mem_cgroup *memcg,
334 list_lru_walk_cb isolate, void *cb_arg,
335 unsigned long *nr_to_walk)
336{
337 return __list_lru_walk_one(lru, nid, memcg, isolate,
338 cb_arg, nr_to_walk, false);
339}
340EXPORT_SYMBOL_GPL(list_lru_walk_one);
341
342unsigned long
343list_lru_walk_one_irq(struct list_lru *lru, int nid, struct mem_cgroup *memcg,
344 list_lru_walk_cb isolate, void *cb_arg,
345 unsigned long *nr_to_walk)
346{
347 return __list_lru_walk_one(lru, nid, memcg, isolate,
348 cb_arg, nr_to_walk, true);
349}
350
351unsigned long list_lru_walk_node(struct list_lru *lru, int nid,
352 list_lru_walk_cb isolate, void *cb_arg,
353 unsigned long *nr_to_walk)
354{
355 long isolated = 0;
356
357 isolated += list_lru_walk_one(lru, nid, NULL, isolate, cb_arg,
358 nr_to_walk);
359
360#ifdef CONFIG_MEMCG
361 if (*nr_to_walk > 0 && list_lru_memcg_aware(lru)) {
362 struct list_lru_memcg *mlru;
363 struct mem_cgroup *memcg;
364 unsigned long index;
365
366 xa_for_each(&lru->xa, index, mlru) {
367 rcu_read_lock();
368 memcg = mem_cgroup_from_id(index);
369 if (!mem_cgroup_tryget(memcg)) {
370 rcu_read_unlock();
371 continue;
372 }
373 rcu_read_unlock();
374 isolated += __list_lru_walk_one(lru, nid, memcg,
375 isolate, cb_arg,
376 nr_to_walk, false);
377 mem_cgroup_put(memcg);
378
379 if (*nr_to_walk <= 0)
380 break;
381 }
382 }
383#endif
384
385 return isolated;
386}
387EXPORT_SYMBOL_GPL(list_lru_walk_node);
388
389static void init_one_lru(struct list_lru *lru, struct list_lru_one *l)
390{
391 INIT_LIST_HEAD(&l->list);
392 spin_lock_init(&l->lock);
393 l->nr_items = 0;
394#ifdef CONFIG_LOCKDEP
395 if (lru->key)
396 lockdep_set_class(&l->lock, lru->key);
397#endif
398}
399
400#ifdef CONFIG_MEMCG
401static struct list_lru_memcg *memcg_init_list_lru_one(struct list_lru *lru, gfp_t gfp)
402{
403 int nid;
404 struct list_lru_memcg *mlru;
405
406 mlru = kmalloc(struct_size(mlru, node, nr_node_ids), gfp);
407 if (!mlru)
408 return NULL;
409
410 for_each_node(nid)
411 init_one_lru(lru, &mlru->node[nid]);
412
413 return mlru;
414}
415
416static inline void memcg_init_list_lru(struct list_lru *lru, bool memcg_aware)
417{
418 if (memcg_aware)
419 xa_init_flags(&lru->xa, XA_FLAGS_LOCK_IRQ);
420 lru->memcg_aware = memcg_aware;
421}
422
423static void memcg_destroy_list_lru(struct list_lru *lru)
424{
425 XA_STATE(xas, &lru->xa, 0);
426 struct list_lru_memcg *mlru;
427
428 if (!list_lru_memcg_aware(lru))
429 return;
430
431 xas_lock_irq(&xas);
432 xas_for_each(&xas, mlru, ULONG_MAX) {
433 kfree(mlru);
434 xas_store(&xas, NULL);
435 }
436 xas_unlock_irq(&xas);
437}
438
439static void memcg_reparent_list_lru_one(struct list_lru *lru, int nid,
440 struct list_lru_one *src,
441 struct mem_cgroup *dst_memcg)
442{
443 int dst_idx = dst_memcg->kmemcg_id;
444 struct list_lru_one *dst;
445
446 spin_lock_irq(&src->lock);
447 dst = list_lru_from_memcg_idx(lru, nid, dst_idx);
448 spin_lock_nested(&dst->lock, SINGLE_DEPTH_NESTING);
449
450 list_splice_init(&src->list, &dst->list);
451 if (src->nr_items) {
452 WARN_ON(src->nr_items < 0);
453 dst->nr_items += src->nr_items;
454 set_shrinker_bit(dst_memcg, nid, lru_shrinker_id(lru));
455 }
456 /* Mark the list_lru_one dead */
457 src->nr_items = LONG_MIN;
458
459 spin_unlock(&dst->lock);
460 spin_unlock_irq(&src->lock);
461}
462
463void memcg_reparent_list_lrus(struct mem_cgroup *memcg, struct mem_cgroup *parent)
464{
465 struct list_lru *lru;
466 int i;
467
468 mutex_lock(&list_lrus_mutex);
469 list_for_each_entry(lru, &memcg_list_lrus, list) {
470 struct list_lru_memcg *mlru;
471 XA_STATE(xas, &lru->xa, memcg->kmemcg_id);
472
473 /*
474 * Lock the Xarray to ensure no on going list_lru_memcg
475 * allocation and further allocation will see css_is_dying().
476 */
477 xas_lock_irq(&xas);
478 mlru = xas_store(&xas, NULL);
479 xas_unlock_irq(&xas);
480 if (!mlru)
481 continue;
482
483 /*
484 * With Xarray value set to NULL, holding the lru lock below
485 * prevents list_lru_{add,del,isolate} from touching the lru,
486 * safe to reparent.
487 */
488 for_each_node(i)
489 memcg_reparent_list_lru_one(lru, i, &mlru->node[i], parent);
490
491 /*
492 * Here all list_lrus corresponding to the cgroup are guaranteed
493 * to remain empty, we can safely free this lru, any further
494 * memcg_list_lru_alloc() call will simply bail out.
495 */
496 kvfree_rcu(mlru, rcu);
497 }
498 mutex_unlock(&list_lrus_mutex);
499}
500
501static inline bool memcg_list_lru_allocated(struct mem_cgroup *memcg,
502 struct list_lru *lru)
503{
504 int idx = memcg->kmemcg_id;
505
506 return idx < 0 || xa_load(&lru->xa, idx);
507}
508
509int memcg_list_lru_alloc(struct mem_cgroup *memcg, struct list_lru *lru,
510 gfp_t gfp)
511{
512 unsigned long flags;
513 struct list_lru_memcg *mlru;
514 struct mem_cgroup *pos, *parent;
515 XA_STATE(xas, &lru->xa, 0);
516
517 if (!list_lru_memcg_aware(lru) || memcg_list_lru_allocated(memcg, lru))
518 return 0;
519
520 gfp &= GFP_RECLAIM_MASK;
521 /*
522 * Because the list_lru can be reparented to the parent cgroup's
523 * list_lru, we should make sure that this cgroup and all its
524 * ancestors have allocated list_lru_memcg.
525 */
526 do {
527 /*
528 * Keep finding the farest parent that wasn't populated
529 * until found memcg itself.
530 */
531 pos = memcg;
532 parent = parent_mem_cgroup(pos);
533 while (!memcg_list_lru_allocated(parent, lru)) {
534 pos = parent;
535 parent = parent_mem_cgroup(pos);
536 }
537
538 mlru = memcg_init_list_lru_one(lru, gfp);
539 if (!mlru)
540 return -ENOMEM;
541 xas_set(&xas, pos->kmemcg_id);
542 do {
543 xas_lock_irqsave(&xas, flags);
544 if (!xas_load(&xas) && !css_is_dying(&pos->css)) {
545 xas_store(&xas, mlru);
546 if (!xas_error(&xas))
547 mlru = NULL;
548 }
549 xas_unlock_irqrestore(&xas, flags);
550 } while (xas_nomem(&xas, gfp));
551 if (mlru)
552 kfree(mlru);
553 } while (pos != memcg && !css_is_dying(&pos->css));
554
555 return xas_error(&xas);
556}
557#else
558static inline void memcg_init_list_lru(struct list_lru *lru, bool memcg_aware)
559{
560}
561
562static void memcg_destroy_list_lru(struct list_lru *lru)
563{
564}
565#endif /* CONFIG_MEMCG */
566
567int __list_lru_init(struct list_lru *lru, bool memcg_aware, struct shrinker *shrinker)
568{
569 int i;
570
571#ifdef CONFIG_MEMCG
572 if (shrinker)
573 lru->shrinker_id = shrinker->id;
574 else
575 lru->shrinker_id = -1;
576
577 if (mem_cgroup_kmem_disabled())
578 memcg_aware = false;
579#endif
580
581 lru->node = kcalloc(nr_node_ids, sizeof(*lru->node), GFP_KERNEL);
582 if (!lru->node)
583 return -ENOMEM;
584
585 for_each_node(i)
586 init_one_lru(lru, &lru->node[i].lru);
587
588 memcg_init_list_lru(lru, memcg_aware);
589 list_lru_register(lru);
590
591 return 0;
592}
593EXPORT_SYMBOL_GPL(__list_lru_init);
594
595void list_lru_destroy(struct list_lru *lru)
596{
597 /* Already destroyed or not yet initialized? */
598 if (!lru->node)
599 return;
600
601 list_lru_unregister(lru);
602
603 memcg_destroy_list_lru(lru);
604 kfree(lru->node);
605 lru->node = NULL;
606
607#ifdef CONFIG_MEMCG
608 lru->shrinker_id = -1;
609#endif
610}
611EXPORT_SYMBOL_GPL(list_lru_destroy);