projects/linux·blob v6.3-rc2 · refs

678 lines · 18.4 KiB

1// SPDX-License-Identifier: GPL-2.0-only
2/* Copyright (c) 2022 Meta Platforms, Inc. and affiliates. */
3#include <linux/mm.h>
4#include <linux/llist.h>
5#include <linux/bpf.h>
6#include <linux/irq_work.h>
7#include <linux/bpf_mem_alloc.h>
8#include <linux/memcontrol.h>
9#include <asm/local.h>
10
11/* Any context (including NMI) BPF specific memory allocator.
12 *
13 * Tracing BPF programs can attach to kprobe and fentry. Hence they
14 * run in unknown context where calling plain kmalloc() might not be safe.
15 *
16 * Front-end kmalloc() with per-cpu per-bucket cache of free elements.
17 * Refill this cache asynchronously from irq_work.
18 *
19 * CPU_0 buckets
20 * 16 32 64 96 128 196 256 512 1024 2048 4096
21 * ...
22 * CPU_N buckets
23 * 16 32 64 96 128 196 256 512 1024 2048 4096
24 *
25 * The buckets are prefilled at the start.
26 * BPF programs always run with migration disabled.
27 * It's safe to allocate from cache of the current cpu with irqs disabled.
28 * Free-ing is always done into bucket of the current cpu as well.
29 * irq_work trims extra free elements from buckets with kfree
30 * and refills them with kmalloc, so global kmalloc logic takes care
31 * of freeing objects allocated by one cpu and freed on another.
32 *
33 * Every allocated objected is padded with extra 8 bytes that contains
34 * struct llist_node.
35 */
36#define LLIST_NODE_SZ sizeof(struct llist_node)
37
38/* similar to kmalloc, but sizeof == 8 bucket is gone */
39static u8 size_index[24] __ro_after_init = {
40 3, /* 8 */
41 3, /* 16 */
42 4, /* 24 */
43 4, /* 32 */
44 5, /* 40 */
45 5, /* 48 */
46 5, /* 56 */
47 5, /* 64 */
48 1, /* 72 */
49 1, /* 80 */
50 1, /* 88 */
51 1, /* 96 */
52 6, /* 104 */
53 6, /* 112 */
54 6, /* 120 */
55 6, /* 128 */
56 2, /* 136 */
57 2, /* 144 */
58 2, /* 152 */
59 2, /* 160 */
60 2, /* 168 */
61 2, /* 176 */
62 2, /* 184 */
63 2 /* 192 */
64};
65
66static int bpf_mem_cache_idx(size_t size)
67{
68 if (!size || size > 4096)
69 return -1;
70
71 if (size <= 192)
72 return size_index[(size - 1) / 8] - 1;
73
74 return fls(size - 1) - 2;
75}
76
77#define NUM_CACHES 11
78
79struct bpf_mem_cache {
80 /* per-cpu list of free objects of size 'unit_size'.
81 * All accesses are done with interrupts disabled and 'active' counter
82 * protection with __llist_add() and __llist_del_first().
83 */
84 struct llist_head free_llist;
85 local_t active;
86
87 /* Operations on the free_list from unit_alloc/unit_free/bpf_mem_refill
88 * are sequenced by per-cpu 'active' counter. But unit_free() cannot
89 * fail. When 'active' is busy the unit_free() will add an object to
90 * free_llist_extra.
91 */
92 struct llist_head free_llist_extra;
93
94 struct irq_work refill_work;
95 struct obj_cgroup *objcg;
96 int unit_size;
97 /* count of objects in free_llist */
98 int free_cnt;
99 int low_watermark, high_watermark, batch;
100 int percpu_size;
101
102 struct rcu_head rcu;
103 struct llist_head free_by_rcu;
104 struct llist_head waiting_for_gp;
105 atomic_t call_rcu_in_progress;
106};
107
108struct bpf_mem_caches {
109 struct bpf_mem_cache cache[NUM_CACHES];
110};
111
112static struct llist_node notrace *__llist_del_first(struct llist_head *head)
113{
114 struct llist_node *entry, *next;
115
116 entry = head->first;
117 if (!entry)
118 return NULL;
119 next = entry->next;
120 head->first = next;
121 return entry;
122}
123
124static void *__alloc(struct bpf_mem_cache *c, int node)
125{
126 /* Allocate, but don't deplete atomic reserves that typical
127 * GFP_ATOMIC would do. irq_work runs on this cpu and kmalloc
128 * will allocate from the current numa node which is what we
129 * want here.
130 */
131 gfp_t flags = GFP_NOWAIT | __GFP_NOWARN | __GFP_ACCOUNT;
132
133 if (c->percpu_size) {
134 void **obj = kmalloc_node(c->percpu_size, flags, node);
135 void *pptr = __alloc_percpu_gfp(c->unit_size, 8, flags);
136
137 if (!obj || !pptr) {
138 free_percpu(pptr);
139 kfree(obj);
140 return NULL;
141 }
142 obj[1] = pptr;
143 return obj;
144 }
145
146 return kmalloc_node(c->unit_size, flags | __GFP_ZERO, node);
147}
148
149static struct mem_cgroup *get_memcg(const struct bpf_mem_cache *c)
150{
151#ifdef CONFIG_MEMCG_KMEM
152 if (c->objcg)
153 return get_mem_cgroup_from_objcg(c->objcg);
154#endif
155
156#ifdef CONFIG_MEMCG
157 return root_mem_cgroup;
158#else
159 return NULL;
160#endif
161}
162
163/* Mostly runs from irq_work except __init phase. */
164static void alloc_bulk(struct bpf_mem_cache *c, int cnt, int node)
165{
166 struct mem_cgroup *memcg = NULL, *old_memcg;
167 unsigned long flags;
168 void *obj;
169 int i;
170
171 memcg = get_memcg(c);
172 old_memcg = set_active_memcg(memcg);
173 for (i = 0; i < cnt; i++) {
174 /*
175 * free_by_rcu is only manipulated by irq work refill_work().
176 * IRQ works on the same CPU are called sequentially, so it is
177 * safe to use __llist_del_first() here. If alloc_bulk() is
178 * invoked by the initial prefill, there will be no running
179 * refill_work(), so __llist_del_first() is fine as well.
180 *
181 * In most cases, objects on free_by_rcu are from the same CPU.
182 * If some objects come from other CPUs, it doesn't incur any
183 * harm because NUMA_NO_NODE means the preference for current
184 * numa node and it is not a guarantee.
185 */
186 obj = __llist_del_first(&c->free_by_rcu);
187 if (!obj) {
188 obj = __alloc(c, node);
189 if (!obj)
190 break;
191 }
192 if (IS_ENABLED(CONFIG_PREEMPT_RT))
193 /* In RT irq_work runs in per-cpu kthread, so disable
194 * interrupts to avoid preemption and interrupts and
195 * reduce the chance of bpf prog executing on this cpu
196 * when active counter is busy.
197 */
198 local_irq_save(flags);
199 /* alloc_bulk runs from irq_work which will not preempt a bpf
200 * program that does unit_alloc/unit_free since IRQs are
201 * disabled there. There is no race to increment 'active'
202 * counter. It protects free_llist from corruption in case NMI
203 * bpf prog preempted this loop.
204 */
205 WARN_ON_ONCE(local_inc_return(&c->active) != 1);
206 __llist_add(obj, &c->free_llist);
207 c->free_cnt++;
208 local_dec(&c->active);
209 if (IS_ENABLED(CONFIG_PREEMPT_RT))
210 local_irq_restore(flags);
211 }
212 set_active_memcg(old_memcg);
213 mem_cgroup_put(memcg);
214}
215
216static void free_one(struct bpf_mem_cache *c, void *obj)
217{
218 if (c->percpu_size) {
219 free_percpu(((void **)obj)[1]);
220 kfree(obj);
221 return;
222 }
223
224 kfree(obj);
225}
226
227static void __free_rcu(struct rcu_head *head)
228{
229 struct bpf_mem_cache *c = container_of(head, struct bpf_mem_cache, rcu);
230 struct llist_node *llnode = llist_del_all(&c->waiting_for_gp);
231 struct llist_node *pos, *t;
232
233 llist_for_each_safe(pos, t, llnode)
234 free_one(c, pos);
235 atomic_set(&c->call_rcu_in_progress, 0);
236}
237
238static void __free_rcu_tasks_trace(struct rcu_head *head)
239{
240 /* If RCU Tasks Trace grace period implies RCU grace period,
241 * there is no need to invoke call_rcu().
242 */
243 if (rcu_trace_implies_rcu_gp())
244 __free_rcu(head);
245 else
246 call_rcu(head, __free_rcu);
247}
248
249static void enque_to_free(struct bpf_mem_cache *c, void *obj)
250{
251 struct llist_node *llnode = obj;
252
253 /* bpf_mem_cache is a per-cpu object. Freeing happens in irq_work.
254 * Nothing races to add to free_by_rcu list.
255 */
256 __llist_add(llnode, &c->free_by_rcu);
257}
258
259static void do_call_rcu(struct bpf_mem_cache *c)
260{
261 struct llist_node *llnode, *t;
262
263 if (atomic_xchg(&c->call_rcu_in_progress, 1))
264 return;
265
266 WARN_ON_ONCE(!llist_empty(&c->waiting_for_gp));
267 llist_for_each_safe(llnode, t, __llist_del_all(&c->free_by_rcu))
268 /* There is no concurrent __llist_add(waiting_for_gp) access.
269 * It doesn't race with llist_del_all either.
270 * But there could be two concurrent llist_del_all(waiting_for_gp):
271 * from __free_rcu() and from drain_mem_cache().
272 */
273 __llist_add(llnode, &c->waiting_for_gp);
274 /* Use call_rcu_tasks_trace() to wait for sleepable progs to finish.
275 * If RCU Tasks Trace grace period implies RCU grace period, free
276 * these elements directly, else use call_rcu() to wait for normal
277 * progs to finish and finally do free_one() on each element.
278 */
279 call_rcu_tasks_trace(&c->rcu, __free_rcu_tasks_trace);
280}
281
282static void free_bulk(struct bpf_mem_cache *c)
283{
284 struct llist_node *llnode, *t;
285 unsigned long flags;
286 int cnt;
287
288 do {
289 if (IS_ENABLED(CONFIG_PREEMPT_RT))
290 local_irq_save(flags);
291 WARN_ON_ONCE(local_inc_return(&c->active) != 1);
292 llnode = __llist_del_first(&c->free_llist);
293 if (llnode)
294 cnt = --c->free_cnt;
295 else
296 cnt = 0;
297 local_dec(&c->active);
298 if (IS_ENABLED(CONFIG_PREEMPT_RT))
299 local_irq_restore(flags);
300 if (llnode)
301 enque_to_free(c, llnode);
302 } while (cnt > (c->high_watermark + c->low_watermark) / 2);
303
304 /* and drain free_llist_extra */
305 llist_for_each_safe(llnode, t, llist_del_all(&c->free_llist_extra))
306 enque_to_free(c, llnode);
307 do_call_rcu(c);
308}
309
310static void bpf_mem_refill(struct irq_work *work)
311{
312 struct bpf_mem_cache *c = container_of(work, struct bpf_mem_cache, refill_work);
313 int cnt;
314
315 /* Racy access to free_cnt. It doesn't need to be 100% accurate */
316 cnt = c->free_cnt;
317 if (cnt < c->low_watermark)
318 /* irq_work runs on this cpu and kmalloc will allocate
319 * from the current numa node which is what we want here.
320 */
321 alloc_bulk(c, c->batch, NUMA_NO_NODE);
322 else if (cnt > c->high_watermark)
323 free_bulk(c);
324}
325
326static void notrace irq_work_raise(struct bpf_mem_cache *c)
327{
328 irq_work_queue(&c->refill_work);
329}
330
331/* For typical bpf map case that uses bpf_mem_cache_alloc and single bucket
332 * the freelist cache will be elem_size * 64 (or less) on each cpu.
333 *
334 * For bpf programs that don't have statically known allocation sizes and
335 * assuming (low_mark + high_mark) / 2 as an average number of elements per
336 * bucket and all buckets are used the total amount of memory in freelists
337 * on each cpu will be:
338 * 64*16 + 64*32 + 64*64 + 64*96 + 64*128 + 64*196 + 64*256 + 32*512 + 16*1024 + 8*2048 + 4*4096
339 * == ~ 116 Kbyte using below heuristic.
340 * Initialized, but unused bpf allocator (not bpf map specific one) will
341 * consume ~ 11 Kbyte per cpu.
342 * Typical case will be between 11K and 116K closer to 11K.
343 * bpf progs can and should share bpf_mem_cache when possible.
344 */
345
346static void prefill_mem_cache(struct bpf_mem_cache *c, int cpu)
347{
348 init_irq_work(&c->refill_work, bpf_mem_refill);
349 if (c->unit_size <= 256) {
350 c->low_watermark = 32;
351 c->high_watermark = 96;
352 } else {
353 /* When page_size == 4k, order-0 cache will have low_mark == 2
354 * and high_mark == 6 with batch alloc of 3 individual pages at
355 * a time.
356 * 8k allocs and above low == 1, high == 3, batch == 1.
357 */
358 c->low_watermark = max(32 * 256 / c->unit_size, 1);
359 c->high_watermark = max(96 * 256 / c->unit_size, 3);
360 }
361 c->batch = max((c->high_watermark - c->low_watermark) / 4 * 3, 1);
362
363 /* To avoid consuming memory assume that 1st run of bpf
364 * prog won't be doing more than 4 map_update_elem from
365 * irq disabled region
366 */
367 alloc_bulk(c, c->unit_size <= 256 ? 4 : 1, cpu_to_node(cpu));
368}
369
370/* When size != 0 bpf_mem_cache for each cpu.
371 * This is typical bpf hash map use case when all elements have equal size.
372 *
373 * When size == 0 allocate 11 bpf_mem_cache-s for each cpu, then rely on
374 * kmalloc/kfree. Max allocation size is 4096 in this case.
375 * This is bpf_dynptr and bpf_kptr use case.
376 */
377int bpf_mem_alloc_init(struct bpf_mem_alloc *ma, int size, bool percpu)
378{
379 static u16 sizes[NUM_CACHES] = {96, 192, 16, 32, 64, 128, 256, 512, 1024, 2048, 4096};
380 struct bpf_mem_caches *cc, __percpu *pcc;
381 struct bpf_mem_cache *c, __percpu *pc;
382 struct obj_cgroup *objcg = NULL;
383 int cpu, i, unit_size, percpu_size = 0;
384
385 if (size) {
386 pc = __alloc_percpu_gfp(sizeof(*pc), 8, GFP_KERNEL);
387 if (!pc)
388 return -ENOMEM;
389
390 if (percpu)
391 /* room for llist_node and per-cpu pointer */
392 percpu_size = LLIST_NODE_SZ + sizeof(void *);
393 else
394 size += LLIST_NODE_SZ; /* room for llist_node */
395 unit_size = size;
396
397#ifdef CONFIG_MEMCG_KMEM
398 if (memcg_bpf_enabled())
399 objcg = get_obj_cgroup_from_current();
400#endif
401 for_each_possible_cpu(cpu) {
402 c = per_cpu_ptr(pc, cpu);
403 c->unit_size = unit_size;
404 c->objcg = objcg;
405 c->percpu_size = percpu_size;
406 prefill_mem_cache(c, cpu);
407 }
408 ma->cache = pc;
409 return 0;
410 }
411
412 /* size == 0 && percpu is an invalid combination */
413 if (WARN_ON_ONCE(percpu))
414 return -EINVAL;
415
416 pcc = __alloc_percpu_gfp(sizeof(*cc), 8, GFP_KERNEL);
417 if (!pcc)
418 return -ENOMEM;
419#ifdef CONFIG_MEMCG_KMEM
420 objcg = get_obj_cgroup_from_current();
421#endif
422 for_each_possible_cpu(cpu) {
423 cc = per_cpu_ptr(pcc, cpu);
424 for (i = 0; i < NUM_CACHES; i++) {
425 c = &cc->cache[i];
426 c->unit_size = sizes[i];
427 c->objcg = objcg;
428 prefill_mem_cache(c, cpu);
429 }
430 }
431 ma->caches = pcc;
432 return 0;
433}
434
435static void drain_mem_cache(struct bpf_mem_cache *c)
436{
437 struct llist_node *llnode, *t;
438
439 /* No progs are using this bpf_mem_cache, but htab_map_free() called
440 * bpf_mem_cache_free() for all remaining elements and they can be in
441 * free_by_rcu or in waiting_for_gp lists, so drain those lists now.
442 *
443 * Except for waiting_for_gp list, there are no concurrent operations
444 * on these lists, so it is safe to use __llist_del_all().
445 */
446 llist_for_each_safe(llnode, t, __llist_del_all(&c->free_by_rcu))
447 free_one(c, llnode);
448 llist_for_each_safe(llnode, t, llist_del_all(&c->waiting_for_gp))
449 free_one(c, llnode);
450 llist_for_each_safe(llnode, t, __llist_del_all(&c->free_llist))
451 free_one(c, llnode);
452 llist_for_each_safe(llnode, t, __llist_del_all(&c->free_llist_extra))
453 free_one(c, llnode);
454}
455
456static void free_mem_alloc_no_barrier(struct bpf_mem_alloc *ma)
457{
458 free_percpu(ma->cache);
459 free_percpu(ma->caches);
460 ma->cache = NULL;
461 ma->caches = NULL;
462}
463
464static void free_mem_alloc(struct bpf_mem_alloc *ma)
465{
466 /* waiting_for_gp lists was drained, but __free_rcu might
467 * still execute. Wait for it now before we freeing percpu caches.
468 *
469 * rcu_barrier_tasks_trace() doesn't imply synchronize_rcu_tasks_trace(),
470 * but rcu_barrier_tasks_trace() and rcu_barrier() below are only used
471 * to wait for the pending __free_rcu_tasks_trace() and __free_rcu(),
472 * so if call_rcu(head, __free_rcu) is skipped due to
473 * rcu_trace_implies_rcu_gp(), it will be OK to skip rcu_barrier() by
474 * using rcu_trace_implies_rcu_gp() as well.
475 */
476 rcu_barrier_tasks_trace();
477 if (!rcu_trace_implies_rcu_gp())
478 rcu_barrier();
479 free_mem_alloc_no_barrier(ma);
480}
481
482static void free_mem_alloc_deferred(struct work_struct *work)
483{
484 struct bpf_mem_alloc *ma = container_of(work, struct bpf_mem_alloc, work);
485
486 free_mem_alloc(ma);
487 kfree(ma);
488}
489
490static void destroy_mem_alloc(struct bpf_mem_alloc *ma, int rcu_in_progress)
491{
492 struct bpf_mem_alloc *copy;
493
494 if (!rcu_in_progress) {
495 /* Fast path. No callbacks are pending, hence no need to do
496 * rcu_barrier-s.
497 */
498 free_mem_alloc_no_barrier(ma);
499 return;
500 }
501
502 copy = kmalloc(sizeof(*ma), GFP_KERNEL);
503 if (!copy) {
504 /* Slow path with inline barrier-s */
505 free_mem_alloc(ma);
506 return;
507 }
508
509 /* Defer barriers into worker to let the rest of map memory to be freed */
510 copy->cache = ma->cache;
511 ma->cache = NULL;
512 copy->caches = ma->caches;
513 ma->caches = NULL;
514 INIT_WORK(&copy->work, free_mem_alloc_deferred);
515 queue_work(system_unbound_wq, &copy->work);
516}
517
518void bpf_mem_alloc_destroy(struct bpf_mem_alloc *ma)
519{
520 struct bpf_mem_caches *cc;
521 struct bpf_mem_cache *c;
522 int cpu, i, rcu_in_progress;
523
524 if (ma->cache) {
525 rcu_in_progress = 0;
526 for_each_possible_cpu(cpu) {
527 c = per_cpu_ptr(ma->cache, cpu);
528 /*
529 * refill_work may be unfinished for PREEMPT_RT kernel
530 * in which irq work is invoked in a per-CPU RT thread.
531 * It is also possible for kernel with
532 * arch_irq_work_has_interrupt() being false and irq
533 * work is invoked in timer interrupt. So waiting for
534 * the completion of irq work to ease the handling of
535 * concurrency.
536 */
537 irq_work_sync(&c->refill_work);
538 drain_mem_cache(c);
539 rcu_in_progress += atomic_read(&c->call_rcu_in_progress);
540 }
541 /* objcg is the same across cpus */
542 if (c->objcg)
543 obj_cgroup_put(c->objcg);
544 destroy_mem_alloc(ma, rcu_in_progress);
545 }
546 if (ma->caches) {
547 rcu_in_progress = 0;
548 for_each_possible_cpu(cpu) {
549 cc = per_cpu_ptr(ma->caches, cpu);
550 for (i = 0; i < NUM_CACHES; i++) {
551 c = &cc->cache[i];
552 irq_work_sync(&c->refill_work);
553 drain_mem_cache(c);
554 rcu_in_progress += atomic_read(&c->call_rcu_in_progress);
555 }
556 }
557 if (c->objcg)
558 obj_cgroup_put(c->objcg);
559 destroy_mem_alloc(ma, rcu_in_progress);
560 }
561}
562
563/* notrace is necessary here and in other functions to make sure
564 * bpf programs cannot attach to them and cause llist corruptions.
565 */
566static void notrace *unit_alloc(struct bpf_mem_cache *c)
567{
568 struct llist_node *llnode = NULL;
569 unsigned long flags;
570 int cnt = 0;
571
572 /* Disable irqs to prevent the following race for majority of prog types:
573 * prog_A
574 * bpf_mem_alloc
575 * preemption or irq -> prog_B
576 * bpf_mem_alloc
577 *
578 * but prog_B could be a perf_event NMI prog.
579 * Use per-cpu 'active' counter to order free_list access between
580 * unit_alloc/unit_free/bpf_mem_refill.
581 */
582 local_irq_save(flags);
583 if (local_inc_return(&c->active) == 1) {
584 llnode = __llist_del_first(&c->free_llist);
585 if (llnode)
586 cnt = --c->free_cnt;
587 }
588 local_dec(&c->active);
589 local_irq_restore(flags);
590
591 WARN_ON(cnt < 0);
592
593 if (cnt < c->low_watermark)
594 irq_work_raise(c);
595 return llnode;
596}
597
598/* Though 'ptr' object could have been allocated on a different cpu
599 * add it to the free_llist of the current cpu.
600 * Let kfree() logic deal with it when it's later called from irq_work.
601 */
602static void notrace unit_free(struct bpf_mem_cache *c, void *ptr)
603{
604 struct llist_node *llnode = ptr - LLIST_NODE_SZ;
605 unsigned long flags;
606 int cnt = 0;
607
608 BUILD_BUG_ON(LLIST_NODE_SZ > 8);
609
610 local_irq_save(flags);
611 if (local_inc_return(&c->active) == 1) {
612 __llist_add(llnode, &c->free_llist);
613 cnt = ++c->free_cnt;
614 } else {
615 /* unit_free() cannot fail. Therefore add an object to atomic
616 * llist. free_bulk() will drain it. Though free_llist_extra is
617 * a per-cpu list we have to use atomic llist_add here, since
618 * it also can be interrupted by bpf nmi prog that does another
619 * unit_free() into the same free_llist_extra.
620 */
621 llist_add(llnode, &c->free_llist_extra);
622 }
623 local_dec(&c->active);
624 local_irq_restore(flags);
625
626 if (cnt > c->high_watermark)
627 /* free few objects from current cpu into global kmalloc pool */
628 irq_work_raise(c);
629}
630
631/* Called from BPF program or from sys_bpf syscall.
632 * In both cases migration is disabled.
633 */
634void notrace *bpf_mem_alloc(struct bpf_mem_alloc *ma, size_t size)
635{
636 int idx;
637 void *ret;
638
639 if (!size)
640 return ZERO_SIZE_PTR;
641
642 idx = bpf_mem_cache_idx(size + LLIST_NODE_SZ);
643 if (idx < 0)
644 return NULL;
645
646 ret = unit_alloc(this_cpu_ptr(ma->caches)->cache + idx);
647 return !ret ? NULL : ret + LLIST_NODE_SZ;
648}
649
650void notrace bpf_mem_free(struct bpf_mem_alloc *ma, void *ptr)
651{
652 int idx;
653
654 if (!ptr)
655 return;
656
657 idx = bpf_mem_cache_idx(ksize(ptr - LLIST_NODE_SZ));
658 if (idx < 0)
659 return;
660
661 unit_free(this_cpu_ptr(ma->caches)->cache + idx, ptr);
662}
663
664void notrace *bpf_mem_cache_alloc(struct bpf_mem_alloc *ma)
665{
666 void *ret;
667
668 ret = unit_alloc(this_cpu_ptr(ma->cache));
669 return !ret ? NULL : ret + LLIST_NODE_SZ;
670}
671
672void notrace bpf_mem_cache_free(struct bpf_mem_alloc *ma, void *ptr)
673{
674 if (!ptr)
675 return;
676
677 unit_free(this_cpu_ptr(ma->cache), ptr);
678}