// SPDX-License-Identifier: GPL-2.0-only
/* Copyright (c) 2022 Meta Platforms, Inc. and affiliates. */
#include <linux/mm.h>
#include <linux/llist.h>
#include <linux/bpf.h>
#include <linux/irq_work.h>
#include <linux/bpf_mem_alloc.h>
#include <linux/memcontrol.h>
#include <asm/local.h>
/* Any context (including NMI) BPF specific memory allocator.
*
* Tracing BPF programs can attach to kprobe and fentry. Hence they
* run in unknown context where calling plain kmalloc() might not be safe.
*
* Front-end kmalloc() with per-cpu per-bucket cache of free elements.
* Refill this cache asynchronously from irq_work.
*
* CPU_0 buckets
* 16 32 64 96 128 196 256 512 1024 2048 4096
* ...
* CPU_N buckets
* 16 32 64 96 128 196 256 512 1024 2048 4096
*
* The buckets are prefilled at the start.
* BPF programs always run with migration disabled.
* It's safe to allocate from cache of the current cpu with irqs disabled.
* Free-ing is always done into bucket of the current cpu as well.
* irq_work trims extra free elements from buckets with kfree
* and refills them with kmalloc, so global kmalloc logic takes care
* of freeing objects allocated by one cpu and freed on another.
*
* Every allocated objected is padded with extra 8 bytes that contains
* struct llist_node.
*/
#define LLIST_NODE_SZ sizeof(struct llist_node)
/* similar to kmalloc, but sizeof == 8 bucket is gone */
static u8 size_index[24] __ro_after_init = {
3, /* 8 */
3, /* 16 */
4, /* 24 */
4, /* 32 */
5, /* 40 */
5, /* 48 */
5, /* 56 */
5, /* 64 */
1, /* 72 */
1, /* 80 */
1, /* 88 */
1, /* 96 */
6, /* 104 */
6, /* 112 */
6, /* 120 */
6, /* 128 */
2, /* 136 */
2, /* 144 */
2, /* 152 */
2, /* 160 */
2, /* 168 */
2, /* 176 */
2, /* 184 */
2 /* 192 */
};
static int bpf_mem_cache_idx(size_t size)
{
if (!size || size > 4096)
return -1;
if (size <= 192)
return size_index[(size - 1) / 8] - 1;
return fls(size - 1) - 2;
}
#define NUM_CACHES 11
struct bpf_mem_cache {
/* per-cpu list of free objects of size 'unit_size'.
* All accesses are done with interrupts disabled and 'active' counter
* protection with __llist_add() and __llist_del_first().
*/
struct llist_head free_llist;
local_t active;
/* Operations on the free_list from unit_alloc/unit_free/bpf_mem_refill
* are sequenced by per-cpu 'active' counter. But unit_free() cannot
* fail. When 'active' is busy the unit_free() will add an object to
* free_llist_extra.
*/
struct llist_head free_llist_extra;
struct irq_work refill_work;
struct obj_cgroup *objcg;
int unit_size;
/* count of objects in free_llist */
int free_cnt;
int low_watermark, high_watermark, batch;
int percpu_size;
bool draining;
struct bpf_mem_cache *tgt;
/* list of objects to be freed after RCU GP */
struct llist_head free_by_rcu;
struct llist_node *free_by_rcu_tail;
struct llist_head waiting_for_gp;
struct llist_node *waiting_for_gp_tail;
struct rcu_head rcu;
atomic_t call_rcu_in_progress;
struct llist_head free_llist_extra_rcu;
/* list of objects to be freed after RCU tasks trace GP */
struct llist_head free_by_rcu_ttrace;
struct llist_head waiting_for_gp_ttrace;
struct rcu_head rcu_ttrace;
atomic_t call_rcu_ttrace_in_progress;
};
struct bpf_mem_caches {
struct bpf_mem_cache cache[NUM_CACHES];
};
static const u16 sizes[NUM_CACHES] = {96, 192, 16, 32, 64, 128, 256, 512, 1024, 2048, 4096};
static struct llist_node notrace *__llist_del_first(struct llist_head *head)
{
struct llist_node *entry, *next;
entry = head->first;
if (!entry)
return NULL;
next = entry->next;
head->first = next;
return entry;
}
static void *__alloc(struct bpf_mem_cache *c, int node, gfp_t flags)
{
if (c->percpu_size) {
void __percpu **obj = kmalloc_node(c->percpu_size, flags, node);
void __percpu *pptr = __alloc_percpu_gfp(c->unit_size, 8, flags);
if (!obj || !pptr) {
free_percpu(pptr);
kfree(obj);
return NULL;
}
obj[1] = pptr;
return obj;
}
return kmalloc_node(c->unit_size, flags | __GFP_ZERO, node);
}
static struct mem_cgroup *get_memcg(const struct bpf_mem_cache *c)
{
#ifdef CONFIG_MEMCG
if (c->objcg)
return get_mem_cgroup_from_objcg(c->objcg);
return root_mem_cgroup;
#else
return NULL;
#endif
}
static void inc_active(struct bpf_mem_cache *c, unsigned long *flags)
{
if (IS_ENABLED(CONFIG_PREEMPT_RT))
/* In RT irq_work runs in per-cpu kthread, so disable
* interrupts to avoid preemption and interrupts and
* reduce the chance of bpf prog executing on this cpu
* when active counter is busy.
*/
local_irq_save(*flags);
/* alloc_bulk runs from irq_work which will not preempt a bpf
* program that does unit_alloc/unit_free since IRQs are
* disabled there. There is no race to increment 'active'
* counter. It protects free_llist from corruption in case NMI
* bpf prog preempted this loop.
*/
WARN_ON_ONCE(local_inc_return(&c->active) != 1);
}
static void dec_active(struct bpf_mem_cache *c, unsigned long *flags)
{
local_dec(&c->active);
if (IS_ENABLED(CONFIG_PREEMPT_RT))
local_irq_restore(*flags);
}
static void add_obj_to_free_list(struct bpf_mem_cache *c, void *obj)
{
unsigned long flags;
inc_active(c, &flags);
__llist_add(obj, &c->free_llist);
c->free_cnt++;
dec_active(c, &flags);
}
/* Mostly runs from irq_work except __init phase. */
static void alloc_bulk(struct bpf_mem_cache *c, int cnt, int node, bool atomic)
{
struct mem_cgroup *memcg = NULL, *old_memcg;
gfp_t gfp;
void *obj;
int i;
gfp = __GFP_NOWARN | __GFP_ACCOUNT;
gfp |= atomic ? GFP_NOWAIT : GFP_KERNEL;
for (i = 0; i < cnt; i++) {
/*
* For every 'c' llist_del_first(&c->free_by_rcu_ttrace); is
* done only by one CPU == current CPU. Other CPUs might
* llist_add() and llist_del_all() in parallel.
*/
obj = llist_del_first(&c->free_by_rcu_ttrace);
if (!obj)
break;
add_obj_to_free_list(c, obj);
}
if (i >= cnt)
return;
for (; i < cnt; i++) {
obj = llist_del_first(&c->waiting_for_gp_ttrace);
if (!obj)
break;
add_obj_to_free_list(c, obj);
}
if (i >= cnt)
return;
memcg = get_memcg(c);
old_memcg = set_active_memcg(memcg);
for (; i < cnt; i++) {
/* Allocate, but don't deplete atomic reserves that typical
* GFP_ATOMIC would do. irq_work runs on this cpu and kmalloc
* will allocate from the current numa node which is what we
* want here.
*/
obj = __alloc(c, node, gfp);
if (!obj)
break;
add_obj_to_free_list(c, obj);
}
set_active_memcg(old_memcg);
mem_cgroup_put(memcg);
}
static void free_one(void *obj, bool percpu)
{
if (percpu) {
free_percpu(((void __percpu **)obj)[1]);
kfree(obj);
return;
}
kfree(obj);
}
static int free_all(struct llist_node *llnode, bool percpu)
{
struct llist_node *pos, *t;
int cnt = 0;
llist_for_each_safe(pos, t, llnode) {
free_one(pos, percpu);
cnt++;
}
return cnt;
}
static void __free_rcu(struct rcu_head *head)
{
struct bpf_mem_cache *c = container_of(head, struct bpf_mem_cache, rcu_ttrace);
free_all(llist_del_all(&c->waiting_for_gp_ttrace), !!c->percpu_size);
atomic_set(&c->call_rcu_ttrace_in_progress, 0);
}
static void __free_rcu_tasks_trace(struct rcu_head *head)
{
/* If RCU Tasks Trace grace period implies RCU grace period,
* there is no need to invoke call_rcu().
*/
if (rcu_trace_implies_rcu_gp())
__free_rcu(head);
else
call_rcu(head, __free_rcu);
}
static void enque_to_free(struct bpf_mem_cache *c, void *obj)
{
struct llist_node *llnode = obj;
/* bpf_mem_cache is a per-cpu object. Freeing happens in irq_work.
* Nothing races to add to free_by_rcu_ttrace list.
*/
llist_add(llnode, &c->free_by_rcu_ttrace);
}
static void do_call_rcu_ttrace(struct bpf_mem_cache *c)
{
struct llist_node *llnode, *t;
if (atomic_xchg(&c->call_rcu_ttrace_in_progress, 1)) {
if (unlikely(READ_ONCE(c->draining))) {
llnode = llist_del_all(&c->free_by_rcu_ttrace);
free_all(llnode, !!c->percpu_size);
}
return;
}
WARN_ON_ONCE(!llist_empty(&c->waiting_for_gp_ttrace));
llist_for_each_safe(llnode, t, llist_del_all(&c->free_by_rcu_ttrace))
llist_add(llnode, &c->waiting_for_gp_ttrace);
if (unlikely(READ_ONCE(c->draining))) {
__free_rcu(&c->rcu_ttrace);
return;
}
/* Use call_rcu_tasks_trace() to wait for sleepable progs to finish.
* If RCU Tasks Trace grace period implies RCU grace period, free
* these elements directly, else use call_rcu() to wait for normal
* progs to finish and finally do free_one() on each element.
*/
call_rcu_tasks_trace(&c->rcu_ttrace, __free_rcu_tasks_trace);
}
static void free_bulk(struct bpf_mem_cache *c)
{
struct bpf_mem_cache *tgt = c->tgt;
struct llist_node *llnode, *t;
unsigned long flags;
int cnt;
WARN_ON_ONCE(tgt->unit_size != c->unit_size);
WARN_ON_ONCE(tgt->percpu_size != c->percpu_size);
do {
inc_active(c, &flags);
llnode = __llist_del_first(&c->free_llist);
if (llnode)
cnt = --c->free_cnt;
else
cnt = 0;
dec_active(c, &flags);
if (llnode)
enque_to_free(tgt, llnode);
} while (cnt > (c->high_watermark + c->low_watermark) / 2);
/* and drain free_llist_extra */
llist_for_each_safe(llnode, t, llist_del_all(&c->free_llist_extra))
enque_to_free(tgt, llnode);
do_call_rcu_ttrace(tgt);
}
static void __free_by_rcu(struct rcu_head *head)
{
struct bpf_mem_cache *c = container_of(head, struct bpf_mem_cache, rcu);
struct bpf_mem_cache *tgt = c->tgt;
struct llist_node *llnode;
WARN_ON_ONCE(tgt->unit_size != c->unit_size);
WARN_ON_ONCE(tgt->percpu_size != c->percpu_size);
llnode = llist_del_all(&c->waiting_for_gp);
if (!llnode)
goto out;
llist_add_batch(llnode, c->waiting_for_gp_tail, &tgt->free_by_rcu_ttrace);
/* Objects went through regular RCU GP. Send them to RCU tasks trace */
do_call_rcu_ttrace(tgt);
out:
atomic_set(&c->call_rcu_in_progress, 0);
}
static void check_free_by_rcu(struct bpf_mem_cache *c)
{
struct llist_node *llnode, *t;
unsigned long flags;
/* drain free_llist_extra_rcu */
if (unlikely(!llist_empty(&c->free_llist_extra_rcu))) {
inc_active(c, &flags);
llist_for_each_safe(llnode, t, llist_del_all(&c->free_llist_extra_rcu))
if (__llist_add(llnode, &c->free_by_rcu))
c->free_by_rcu_tail = llnode;
dec_active(c, &flags);
}
if (llist_empty(&c->free_by_rcu))
return;
if (atomic_xchg(&c->call_rcu_in_progress, 1)) {
/*
* Instead of kmalloc-ing new rcu_head and triggering 10k
* call_rcu() to hit rcutree.qhimark and force RCU to notice
* the overload just ask RCU to hurry up. There could be many
* objects in free_by_rcu list.
* This hint reduces memory consumption for an artificial
* benchmark from 2 Gbyte to 150 Mbyte.
*/
rcu_request_urgent_qs_task(current);
return;
}
WARN_ON_ONCE(!llist_empty(&c->waiting_for_gp));
inc_active(c, &flags);
WRITE_ONCE(c->waiting_for_gp.first, __llist_del_all(&c->free_by_rcu));
c->waiting_for_gp_tail = c->free_by_rcu_tail;
dec_active(c, &flags);
if (unlikely(READ_ONCE(c->draining))) {
free_all(llist_del_all(&c->waiting_for_gp), !!c->percpu_size);
atomic_set(&c->call_rcu_in_progress, 0);
} else {
call_rcu_hurry(&c->rcu, __free_by_rcu);
}
}
static void bpf_mem_refill(struct irq_work *work)
{
struct bpf_mem_cache *c = container_of(work, struct bpf_mem_cache, refill_work);
int cnt;
/* Racy access to free_cnt. It doesn't need to be 100% accurate */
cnt = c->free_cnt;
if (cnt < c->low_watermark)
/* irq_work runs on this cpu and kmalloc will allocate
* from the current numa node which is what we want here.
*/
alloc_bulk(c, c->batch, NUMA_NO_NODE, true);
else if (cnt > c->high_watermark)
free_bulk(c);
check_free_by_rcu(c);
}
static void notrace irq_work_raise(struct bpf_mem_cache *c)
{
irq_work_queue(&c->refill_work);
}
/* For typical bpf map case that uses bpf_mem_cache_alloc and single bucket
* the freelist cache will be elem_size * 64 (or less) on each cpu.
*
* For bpf programs that don't have statically known allocation sizes and
* assuming (low_mark + high_mark) / 2 as an average number of elements per
* bucket and all buckets are used the total amount of memory in freelists
* on each cpu will be:
* 64*16 + 64*32 + 64*64 + 64*96 + 64*128 + 64*196 + 64*256 + 32*512 + 16*1024 + 8*2048 + 4*4096
* == ~ 116 Kbyte using below heuristic.
* Initialized, but unused bpf allocator (not bpf map specific one) will
* consume ~ 11 Kbyte per cpu.
* Typical case will be between 11K and 116K closer to 11K.
* bpf progs can and should share bpf_mem_cache when possible.
*
* Percpu allocation is typically rare. To avoid potential unnecessary large
* memory consumption, set low_mark = 1 and high_mark = 3, resulting in c->batch = 1.
*/
static void init_refill_work(struct bpf_mem_cache *c)
{
init_irq_work(&c->refill_work, bpf_mem_refill);
if (c->percpu_size) {
c->low_watermark = 1;
c->high_watermark = 3;
} else if (c->unit_size <= 256) {
c->low_watermark = 32;
c->high_watermark = 96;
} else {
/* When page_size == 4k, order-0 cache will have low_mark == 2
* and high_mark == 6 with batch alloc of 3 individual pages at
* a time.
* 8k allocs and above low == 1, high == 3, batch == 1.
*/
c->low_watermark = max(32 * 256 / c->unit_size, 1);
c->high_watermark = max(96 * 256 / c->unit_size, 3);
}
c->batch = max((c->high_watermark - c->low_watermark) / 4 * 3, 1);
}
static void prefill_mem_cache(struct bpf_mem_cache *c, int cpu)
{
int cnt = 1;
/* To avoid consuming memory, for non-percpu allocation, assume that
* 1st run of bpf prog won't be doing more than 4 map_update_elem from
* irq disabled region if unit size is less than or equal to 256.
* For all other cases, let us just do one allocation.
*/
if (!c->percpu_size && c->unit_size <= 256)
cnt = 4;
alloc_bulk(c, cnt, cpu_to_node(cpu), false);
}
/* When size != 0 bpf_mem_cache for each cpu.
* This is typical bpf hash map use case when all elements have equal size.
*
* When size == 0 allocate 11 bpf_mem_cache-s for each cpu, then rely on
* kmalloc/kfree. Max allocation size is 4096 in this case.
* This is bpf_dynptr and bpf_kptr use case.
*/
int bpf_mem_alloc_init(struct bpf_mem_alloc *ma, int size, bool percpu)
{
struct bpf_mem_caches *cc; struct bpf_mem_caches __percpu *pcc;
struct bpf_mem_cache *c; struct bpf_mem_cache __percpu *pc;
struct obj_cgroup *objcg = NULL;
int cpu, i, unit_size, percpu_size = 0;
if (percpu && size == 0)
return -EINVAL;
/* room for llist_node and per-cpu pointer */
if (percpu)
percpu_size = LLIST_NODE_SZ + sizeof(void *);
ma->percpu = percpu;
if (size) {
pc = __alloc_percpu_gfp(sizeof(*pc), 8, GFP_KERNEL);
if (!pc)
return -ENOMEM;
if (!percpu)
size += LLIST_NODE_SZ; /* room for llist_node */
unit_size = size;
#ifdef CONFIG_MEMCG
if (memcg_bpf_enabled())
objcg = get_obj_cgroup_from_current();
#endif
ma->objcg = objcg;
for_each_possible_cpu(cpu) {
c = per_cpu_ptr(pc, cpu);
c->unit_size = unit_size;
c->objcg = objcg;
c->percpu_size = percpu_size;
c->tgt = c;
init_refill_work(c);
prefill_mem_cache(c, cpu);
}
ma->cache = pc;
return 0;
}
pcc = __alloc_percpu_gfp(sizeof(*cc), 8, GFP_KERNEL);
if (!pcc)
return -ENOMEM;
#ifdef CONFIG_MEMCG
objcg = get_obj_cgroup_from_current();
#endif
ma->objcg = objcg;
for_each_possible_cpu(cpu) {
cc = per_cpu_ptr(pcc, cpu);
for (i = 0; i < NUM_CACHES; i++) {
c = &cc->cache[i];
c->unit_size = sizes[i];
c->objcg = objcg;
c->percpu_size = percpu_size;
c->tgt = c;
init_refill_work(c);
prefill_mem_cache(c, cpu);
}
}
ma->caches = pcc;
return 0;
}
int bpf_mem_alloc_percpu_init(struct bpf_mem_alloc *ma, struct obj_cgroup *objcg)
{
struct bpf_mem_caches __percpu *pcc;
pcc = __alloc_percpu_gfp(sizeof(struct bpf_mem_caches), 8, GFP_KERNEL);
if (!pcc)
return -ENOMEM;
ma->caches = pcc;
ma->objcg = objcg;
ma->percpu = true;
return 0;
}
int bpf_mem_alloc_percpu_unit_init(struct bpf_mem_alloc *ma, int size)
{
struct bpf_mem_caches *cc; struct bpf_mem_caches __percpu *pcc;
int cpu, i, unit_size, percpu_size;
struct obj_cgroup *objcg;
struct bpf_mem_cache *c;
i = bpf_mem_cache_idx(size);
if (i < 0)
return -EINVAL;
/* room for llist_node and per-cpu pointer */
percpu_size = LLIST_NODE_SZ + sizeof(void *);
unit_size = sizes[i];
objcg = ma->objcg;
pcc = ma->caches;
for_each_possible_cpu(cpu) {
cc = per_cpu_ptr(pcc, cpu);
c = &cc->cache[i];
if (c->unit_size)
break;
c->unit_size = unit_size;
c->objcg = objcg;
c->percpu_size = percpu_size;
c->tgt = c;
init_refill_work(c);
prefill_mem_cache(c, cpu);
}
return 0;
}
static void drain_mem_cache(struct bpf_mem_cache *c)
{
bool percpu = !!c->percpu_size;
/* No progs are using this bpf_mem_cache, but htab_map_free() called
* bpf_mem_cache_free() for all remaining elements and they can be in
* free_by_rcu_ttrace or in waiting_for_gp_ttrace lists, so drain those lists now.
*
* Except for waiting_for_gp_ttrace list, there are no concurrent operations
* on these lists, so it is safe to use __llist_del_all().
*/
free_all(llist_del_all(&c->free_by_rcu_ttrace), percpu);
free_all(llist_del_all(&c->waiting_for_gp_ttrace), percpu);
free_all(__llist_del_all(&c->free_llist), percpu);
free_all(__llist_del_all(&c->free_llist_extra), percpu);
free_all(__llist_del_all(&c->free_by_rcu), percpu);
free_all(__llist_del_all(&c->free_llist_extra_rcu), percpu);
free_all(llist_del_all(&c->waiting_for_gp), percpu);
}
static void check_mem_cache(struct bpf_mem_cache *c)
{
WARN_ON_ONCE(!llist_empty(&c->free_by_rcu_ttrace));
WARN_ON_ONCE(!llist_empty(&c->waiting_for_gp_ttrace));
WARN_ON_ONCE(!llist_empty(&c->free_llist));
WARN_ON_ONCE(!llist_empty(&c->free_llist_extra));
WARN_ON_ONCE(!llist_empty(&c->free_by_rcu));
WARN_ON_ONCE(!llist_empty(&c->free_llist_extra_rcu));
WARN_ON_ONCE(!llist_empty(&c->waiting_for_gp));
}
static void check_leaked_objs(struct bpf_mem_alloc *ma)
{
struct bpf_mem_caches *cc;
struct bpf_mem_cache *c;
int cpu, i;
if (ma->cache) {
for_each_possible_cpu(cpu) {
c = per_cpu_ptr(ma->cache, cpu);
check_mem_cache(c);
}
}
if (ma->caches) {
for_each_possible_cpu(cpu) {
cc = per_cpu_ptr(ma->caches, cpu);
for (i = 0; i < NUM_CACHES; i++) {
c = &cc->cache[i];
check_mem_cache(c);
}
}
}
}
static void free_mem_alloc_no_barrier(struct bpf_mem_alloc *ma)
{
check_leaked_objs(ma);
free_percpu(ma->cache);
free_percpu(ma->caches);
ma->cache = NULL;
ma->caches = NULL;
}
static void free_mem_alloc(struct bpf_mem_alloc *ma)
{
/* waiting_for_gp[_ttrace] lists were drained, but RCU callbacks
* might still execute. Wait for them.
*
* rcu_barrier_tasks_trace() doesn't imply synchronize_rcu_tasks_trace(),
* but rcu_barrier_tasks_trace() and rcu_barrier() below are only used
* to wait for the pending __free_rcu_tasks_trace() and __free_rcu(),
* so if call_rcu(head, __free_rcu) is skipped due to
* rcu_trace_implies_rcu_gp(), it will be OK to skip rcu_barrier() by
* using rcu_trace_implies_rcu_gp() as well.
*/
rcu_barrier(); /* wait for __free_by_rcu */
rcu_barrier_tasks_trace(); /* wait for __free_rcu */
if (!rcu_trace_implies_rcu_gp())
rcu_barrier();
free_mem_alloc_no_barrier(ma);
}
static void free_mem_alloc_deferred(struct work_struct *work)
{
struct bpf_mem_alloc *ma = container_of(work, struct bpf_mem_alloc, work);
free_mem_alloc(ma);
kfree(ma);
}
static void destroy_mem_alloc(struct bpf_mem_alloc *ma, int rcu_in_progress)
{
struct bpf_mem_alloc *copy;
if (!rcu_in_progress) {
/* Fast path. No callbacks are pending, hence no need to do
* rcu_barrier-s.
*/
free_mem_alloc_no_barrier(ma);
return;
}
copy = kmemdup(ma, sizeof(*ma), GFP_KERNEL);
if (!copy) {
/* Slow path with inline barrier-s */
free_mem_alloc(ma);
return;
}
/* Defer barriers into worker to let the rest of map memory to be freed */
memset(ma, 0, sizeof(*ma));
INIT_WORK(©->work, free_mem_alloc_deferred);
queue_work(system_unbound_wq, ©->work);
}
void bpf_mem_alloc_destroy(struct bpf_mem_alloc *ma)
{
struct bpf_mem_caches *cc;
struct bpf_mem_cache *c;
int cpu, i, rcu_in_progress;
if (ma->cache) {
rcu_in_progress = 0;
for_each_possible_cpu(cpu) {
c = per_cpu_ptr(ma->cache, cpu);
WRITE_ONCE(c->draining, true);
irq_work_sync(&c->refill_work);
drain_mem_cache(c);
rcu_in_progress += atomic_read(&c->call_rcu_ttrace_in_progress);
rcu_in_progress += atomic_read(&c->call_rcu_in_progress);
}
obj_cgroup_put(ma->objcg);
destroy_mem_alloc(ma, rcu_in_progress);
}
if (ma->caches) {
rcu_in_progress = 0;
for_each_possible_cpu(cpu) {
cc = per_cpu_ptr(ma->caches, cpu);
for (i = 0; i < NUM_CACHES; i++) {
c = &cc->cache[i];
WRITE_ONCE(c->draining, true);
irq_work_sync(&c->refill_work);
drain_mem_cache(c);
rcu_in_progress += atomic_read(&c->call_rcu_ttrace_in_progress);
rcu_in_progress += atomic_read(&c->call_rcu_in_progress);
}
}
obj_cgroup_put(ma->objcg);
destroy_mem_alloc(ma, rcu_in_progress);
}
}
/* notrace is necessary here and in other functions to make sure
* bpf programs cannot attach to them and cause llist corruptions.
*/
static void notrace *unit_alloc(struct bpf_mem_cache *c)
{
struct llist_node *llnode = NULL;
unsigned long flags;
int cnt = 0;
/* Disable irqs to prevent the following race for majority of prog types:
* prog_A
* bpf_mem_alloc
* preemption or irq -> prog_B
* bpf_mem_alloc
*
* but prog_B could be a perf_event NMI prog.
* Use per-cpu 'active' counter to order free_list access between
* unit_alloc/unit_free/bpf_mem_refill.
*/
local_irq_save(flags);
if (local_inc_return(&c->active) == 1) {
llnode = __llist_del_first(&c->free_llist);
if (llnode) {
cnt = --c->free_cnt;
*(struct bpf_mem_cache **)llnode = c;
}
}
local_dec(&c->active);
WARN_ON(cnt < 0);
if (cnt < c->low_watermark)
irq_work_raise(c);
/* Enable IRQ after the enqueue of irq work completes, so irq work
* will run after IRQ is enabled and free_llist may be refilled by
* irq work before other task preempts current task.
*/
local_irq_restore(flags);
return llnode;
}
/* Though 'ptr' object could have been allocated on a different cpu
* add it to the free_llist of the current cpu.
* Let kfree() logic deal with it when it's later called from irq_work.
*/
static void notrace unit_free(struct bpf_mem_cache *c, void *ptr)
{
struct llist_node *llnode = ptr - LLIST_NODE_SZ;
unsigned long flags;
int cnt = 0;
BUILD_BUG_ON(LLIST_NODE_SZ > 8);
/*
* Remember bpf_mem_cache that allocated this object.
* The hint is not accurate.
*/
c->tgt = *(struct bpf_mem_cache **)llnode;
local_irq_save(flags);
if (local_inc_return(&c->active) == 1) {
__llist_add(llnode, &c->free_llist);
cnt = ++c->free_cnt;
} else {
/* unit_free() cannot fail. Therefore add an object to atomic
* llist. free_bulk() will drain it. Though free_llist_extra is
* a per-cpu list we have to use atomic llist_add here, since
* it also can be interrupted by bpf nmi prog that does another
* unit_free() into the same free_llist_extra.
*/
llist_add(llnode, &c->free_llist_extra);
}
local_dec(&c->active);
if (cnt > c->high_watermark)
/* free few objects from current cpu into global kmalloc pool */
irq_work_raise(c);
/* Enable IRQ after irq_work_raise() completes, otherwise when current
* task is preempted by task which does unit_alloc(), unit_alloc() may
* return NULL unexpectedly because irq work is already pending but can
* not been triggered and free_llist can not be refilled timely.
*/
local_irq_restore(flags);
}
static void notrace unit_free_rcu(struct bpf_mem_cache *c, void *ptr)
{
struct llist_node *llnode = ptr - LLIST_NODE_SZ;
unsigned long flags;
c->tgt = *(struct bpf_mem_cache **)llnode;
local_irq_save(flags);
if (local_inc_return(&c->active) == 1) {
if (__llist_add(llnode, &c->free_by_rcu))
c->free_by_rcu_tail = llnode;
} else {
llist_add(llnode, &c->free_llist_extra_rcu);
}
local_dec(&c->active);
if (!atomic_read(&c->call_rcu_in_progress))
irq_work_raise(c);
local_irq_restore(flags);
}
/* Called from BPF program or from sys_bpf syscall.
* In both cases migration is disabled.
*/
void notrace *bpf_mem_alloc(struct bpf_mem_alloc *ma, size_t size)
{
int idx;
void *ret;
if (!size)
return NULL;
if (!ma->percpu)
size += LLIST_NODE_SZ;
idx = bpf_mem_cache_idx(size);
if (idx < 0)
return NULL;
ret = unit_alloc(this_cpu_ptr(ma->caches)->cache + idx);
return !ret ? NULL : ret + LLIST_NODE_SZ;
}
void notrace bpf_mem_free(struct bpf_mem_alloc *ma, void *ptr)
{
struct bpf_mem_cache *c;
int idx;
if (!ptr)
return;
c = *(void **)(ptr - LLIST_NODE_SZ);
idx = bpf_mem_cache_idx(c->unit_size);
if (WARN_ON_ONCE(idx < 0))
return;
unit_free(this_cpu_ptr(ma->caches)->cache + idx, ptr);
}
void notrace bpf_mem_free_rcu(struct bpf_mem_alloc *ma, void *ptr)
{
struct bpf_mem_cache *c;
int idx;
if (!ptr)
return;
c = *(void **)(ptr - LLIST_NODE_SZ);
idx = bpf_mem_cache_idx(c->unit_size);
if (WARN_ON_ONCE(idx < 0))
return;
unit_free_rcu(this_cpu_ptr(ma->caches)->cache + idx, ptr);
}
void notrace *bpf_mem_cache_alloc(struct bpf_mem_alloc *ma)
{
void *ret;
ret = unit_alloc(this_cpu_ptr(ma->cache));
return !ret ? NULL : ret + LLIST_NODE_SZ;
}
void notrace bpf_mem_cache_free(struct bpf_mem_alloc *ma, void *ptr)
{
if (!ptr)
return;
unit_free(this_cpu_ptr(ma->cache), ptr);
}
void notrace bpf_mem_cache_free_rcu(struct bpf_mem_alloc *ma, void *ptr)
{
if (!ptr)
return;
unit_free_rcu(this_cpu_ptr(ma->cache), ptr);
}
/* Directly does a kfree() without putting 'ptr' back to the free_llist
* for reuse and without waiting for a rcu_tasks_trace gp.
* The caller must first go through the rcu_tasks_trace gp for 'ptr'
* before calling bpf_mem_cache_raw_free().
* It could be used when the rcu_tasks_trace callback does not have
* a hold on the original bpf_mem_alloc object that allocated the
* 'ptr'. This should only be used in the uncommon code path.
* Otherwise, the bpf_mem_alloc's free_llist cannot be refilled
* and may affect performance.
*/
void bpf_mem_cache_raw_free(void *ptr)
{
if (!ptr)
return;
kfree(ptr - LLIST_NODE_SZ);
}
/* When flags == GFP_KERNEL, it signals that the caller will not cause
* deadlock when using kmalloc. bpf_mem_cache_alloc_flags() will use
* kmalloc if the free_llist is empty.
*/
void notrace *bpf_mem_cache_alloc_flags(struct bpf_mem_alloc *ma, gfp_t flags)
{
struct bpf_mem_cache *c;
void *ret;
c = this_cpu_ptr(ma->cache);
ret = unit_alloc(c);
if (!ret && flags == GFP_KERNEL) {
struct mem_cgroup *memcg, *old_memcg;
memcg = get_memcg(c);
old_memcg = set_active_memcg(memcg);
ret = __alloc(c, NUMA_NO_NODE, GFP_KERNEL | __GFP_NOWARN | __GFP_ACCOUNT);
if (ret)
*(struct bpf_mem_cache **)ret = c;
set_active_memcg(old_memcg);
mem_cgroup_put(memcg);
}
return !ret ? NULL : ret + LLIST_NODE_SZ;
}
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