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synced 2024-09-06 18:01:05 +00:00
![Yonghong Song](/assets/img/avatar_default.png)
After merging the patch set [1] to reduce memory usage for bpf_global_percpu_ma, Alexei found a redundant check (cpu == 0) in function bpf_mem_alloc_percpu_unit_init() ([2]). Indeed, the check is unnecessary since c->unit_size will be all NULL or all non-NULL for all cpus before for_each_possible_cpu() loop. Removing the check makes code less confusing. [1] https://lore.kernel.org/all/20231222031729.1287957-1-yonghong.song@linux.dev/ [2] https://lore.kernel.org/all/20231222031745.1289082-1-yonghong.song@linux.dev/ Signed-off-by: Yonghong Song <yonghong.song@linux.dev> Link: https://lore.kernel.org/r/20240104165744.702239-1-yonghong.song@linux.dev Signed-off-by: Alexei Starovoitov <ast@kernel.org>
1013 lines
26 KiB
C
1013 lines
26 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/* Copyright (c) 2022 Meta Platforms, Inc. and affiliates. */
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#include <linux/mm.h>
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#include <linux/llist.h>
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#include <linux/bpf.h>
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#include <linux/irq_work.h>
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#include <linux/bpf_mem_alloc.h>
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#include <linux/memcontrol.h>
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#include <asm/local.h>
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/* Any context (including NMI) BPF specific memory allocator.
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*
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* Tracing BPF programs can attach to kprobe and fentry. Hence they
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* run in unknown context where calling plain kmalloc() might not be safe.
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*
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* Front-end kmalloc() with per-cpu per-bucket cache of free elements.
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* Refill this cache asynchronously from irq_work.
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*
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* CPU_0 buckets
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* 16 32 64 96 128 196 256 512 1024 2048 4096
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* ...
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* CPU_N buckets
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* 16 32 64 96 128 196 256 512 1024 2048 4096
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*
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* The buckets are prefilled at the start.
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* BPF programs always run with migration disabled.
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* It's safe to allocate from cache of the current cpu with irqs disabled.
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* Free-ing is always done into bucket of the current cpu as well.
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* irq_work trims extra free elements from buckets with kfree
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* and refills them with kmalloc, so global kmalloc logic takes care
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* of freeing objects allocated by one cpu and freed on another.
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*
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* Every allocated objected is padded with extra 8 bytes that contains
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* struct llist_node.
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*/
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#define LLIST_NODE_SZ sizeof(struct llist_node)
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/* similar to kmalloc, but sizeof == 8 bucket is gone */
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static u8 size_index[24] __ro_after_init = {
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3, /* 8 */
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3, /* 16 */
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4, /* 24 */
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4, /* 32 */
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5, /* 40 */
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5, /* 48 */
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5, /* 56 */
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5, /* 64 */
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1, /* 72 */
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1, /* 80 */
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1, /* 88 */
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1, /* 96 */
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6, /* 104 */
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6, /* 112 */
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6, /* 120 */
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6, /* 128 */
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2, /* 136 */
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2, /* 144 */
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2, /* 152 */
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2, /* 160 */
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2, /* 168 */
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2, /* 176 */
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2, /* 184 */
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2 /* 192 */
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};
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static int bpf_mem_cache_idx(size_t size)
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{
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if (!size || size > 4096)
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return -1;
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if (size <= 192)
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return size_index[(size - 1) / 8] - 1;
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return fls(size - 1) - 2;
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}
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#define NUM_CACHES 11
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struct bpf_mem_cache {
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/* per-cpu list of free objects of size 'unit_size'.
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* All accesses are done with interrupts disabled and 'active' counter
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* protection with __llist_add() and __llist_del_first().
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*/
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struct llist_head free_llist;
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local_t active;
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/* Operations on the free_list from unit_alloc/unit_free/bpf_mem_refill
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* are sequenced by per-cpu 'active' counter. But unit_free() cannot
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* fail. When 'active' is busy the unit_free() will add an object to
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* free_llist_extra.
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*/
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struct llist_head free_llist_extra;
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struct irq_work refill_work;
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struct obj_cgroup *objcg;
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int unit_size;
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/* count of objects in free_llist */
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int free_cnt;
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int low_watermark, high_watermark, batch;
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int percpu_size;
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bool draining;
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struct bpf_mem_cache *tgt;
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/* list of objects to be freed after RCU GP */
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struct llist_head free_by_rcu;
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struct llist_node *free_by_rcu_tail;
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struct llist_head waiting_for_gp;
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struct llist_node *waiting_for_gp_tail;
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struct rcu_head rcu;
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atomic_t call_rcu_in_progress;
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struct llist_head free_llist_extra_rcu;
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/* list of objects to be freed after RCU tasks trace GP */
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struct llist_head free_by_rcu_ttrace;
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struct llist_head waiting_for_gp_ttrace;
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struct rcu_head rcu_ttrace;
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atomic_t call_rcu_ttrace_in_progress;
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};
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struct bpf_mem_caches {
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struct bpf_mem_cache cache[NUM_CACHES];
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};
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static const u16 sizes[NUM_CACHES] = {96, 192, 16, 32, 64, 128, 256, 512, 1024, 2048, 4096};
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static struct llist_node notrace *__llist_del_first(struct llist_head *head)
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{
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struct llist_node *entry, *next;
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entry = head->first;
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if (!entry)
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return NULL;
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next = entry->next;
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head->first = next;
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return entry;
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}
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static void *__alloc(struct bpf_mem_cache *c, int node, gfp_t flags)
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{
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if (c->percpu_size) {
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void **obj = kmalloc_node(c->percpu_size, flags, node);
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void *pptr = __alloc_percpu_gfp(c->unit_size, 8, flags);
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if (!obj || !pptr) {
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free_percpu(pptr);
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kfree(obj);
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return NULL;
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}
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obj[1] = pptr;
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return obj;
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}
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return kmalloc_node(c->unit_size, flags | __GFP_ZERO, node);
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}
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static struct mem_cgroup *get_memcg(const struct bpf_mem_cache *c)
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{
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#ifdef CONFIG_MEMCG_KMEM
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if (c->objcg)
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return get_mem_cgroup_from_objcg(c->objcg);
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#endif
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#ifdef CONFIG_MEMCG
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return root_mem_cgroup;
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#else
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return NULL;
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#endif
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}
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static void inc_active(struct bpf_mem_cache *c, unsigned long *flags)
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{
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if (IS_ENABLED(CONFIG_PREEMPT_RT))
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/* In RT irq_work runs in per-cpu kthread, so disable
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* interrupts to avoid preemption and interrupts and
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* reduce the chance of bpf prog executing on this cpu
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* when active counter is busy.
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*/
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local_irq_save(*flags);
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/* alloc_bulk runs from irq_work which will not preempt a bpf
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* program that does unit_alloc/unit_free since IRQs are
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* disabled there. There is no race to increment 'active'
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* counter. It protects free_llist from corruption in case NMI
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* bpf prog preempted this loop.
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*/
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WARN_ON_ONCE(local_inc_return(&c->active) != 1);
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}
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static void dec_active(struct bpf_mem_cache *c, unsigned long *flags)
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{
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local_dec(&c->active);
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if (IS_ENABLED(CONFIG_PREEMPT_RT))
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local_irq_restore(*flags);
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}
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static void add_obj_to_free_list(struct bpf_mem_cache *c, void *obj)
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{
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unsigned long flags;
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inc_active(c, &flags);
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__llist_add(obj, &c->free_llist);
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c->free_cnt++;
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dec_active(c, &flags);
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}
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/* Mostly runs from irq_work except __init phase. */
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static void alloc_bulk(struct bpf_mem_cache *c, int cnt, int node, bool atomic)
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{
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struct mem_cgroup *memcg = NULL, *old_memcg;
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gfp_t gfp;
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void *obj;
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int i;
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gfp = __GFP_NOWARN | __GFP_ACCOUNT;
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gfp |= atomic ? GFP_NOWAIT : GFP_KERNEL;
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for (i = 0; i < cnt; i++) {
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/*
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* For every 'c' llist_del_first(&c->free_by_rcu_ttrace); is
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* done only by one CPU == current CPU. Other CPUs might
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* llist_add() and llist_del_all() in parallel.
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*/
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obj = llist_del_first(&c->free_by_rcu_ttrace);
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if (!obj)
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break;
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add_obj_to_free_list(c, obj);
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}
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if (i >= cnt)
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return;
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for (; i < cnt; i++) {
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obj = llist_del_first(&c->waiting_for_gp_ttrace);
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if (!obj)
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break;
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add_obj_to_free_list(c, obj);
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}
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if (i >= cnt)
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return;
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memcg = get_memcg(c);
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old_memcg = set_active_memcg(memcg);
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for (; i < cnt; i++) {
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/* Allocate, but don't deplete atomic reserves that typical
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* GFP_ATOMIC would do. irq_work runs on this cpu and kmalloc
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* will allocate from the current numa node which is what we
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* want here.
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*/
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obj = __alloc(c, node, gfp);
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if (!obj)
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break;
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add_obj_to_free_list(c, obj);
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}
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set_active_memcg(old_memcg);
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mem_cgroup_put(memcg);
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}
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static void free_one(void *obj, bool percpu)
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{
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if (percpu) {
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free_percpu(((void **)obj)[1]);
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kfree(obj);
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return;
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}
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kfree(obj);
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}
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static int free_all(struct llist_node *llnode, bool percpu)
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{
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struct llist_node *pos, *t;
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int cnt = 0;
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llist_for_each_safe(pos, t, llnode) {
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free_one(pos, percpu);
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cnt++;
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}
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return cnt;
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}
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static void __free_rcu(struct rcu_head *head)
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{
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struct bpf_mem_cache *c = container_of(head, struct bpf_mem_cache, rcu_ttrace);
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free_all(llist_del_all(&c->waiting_for_gp_ttrace), !!c->percpu_size);
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atomic_set(&c->call_rcu_ttrace_in_progress, 0);
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}
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static void __free_rcu_tasks_trace(struct rcu_head *head)
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{
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/* If RCU Tasks Trace grace period implies RCU grace period,
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* there is no need to invoke call_rcu().
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*/
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if (rcu_trace_implies_rcu_gp())
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__free_rcu(head);
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else
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call_rcu(head, __free_rcu);
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}
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static void enque_to_free(struct bpf_mem_cache *c, void *obj)
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{
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struct llist_node *llnode = obj;
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/* bpf_mem_cache is a per-cpu object. Freeing happens in irq_work.
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* Nothing races to add to free_by_rcu_ttrace list.
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*/
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llist_add(llnode, &c->free_by_rcu_ttrace);
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}
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static void do_call_rcu_ttrace(struct bpf_mem_cache *c)
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{
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struct llist_node *llnode, *t;
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if (atomic_xchg(&c->call_rcu_ttrace_in_progress, 1)) {
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if (unlikely(READ_ONCE(c->draining))) {
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llnode = llist_del_all(&c->free_by_rcu_ttrace);
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free_all(llnode, !!c->percpu_size);
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}
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return;
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}
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WARN_ON_ONCE(!llist_empty(&c->waiting_for_gp_ttrace));
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llist_for_each_safe(llnode, t, llist_del_all(&c->free_by_rcu_ttrace))
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llist_add(llnode, &c->waiting_for_gp_ttrace);
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if (unlikely(READ_ONCE(c->draining))) {
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__free_rcu(&c->rcu_ttrace);
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return;
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}
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/* Use call_rcu_tasks_trace() to wait for sleepable progs to finish.
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* If RCU Tasks Trace grace period implies RCU grace period, free
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* these elements directly, else use call_rcu() to wait for normal
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* progs to finish and finally do free_one() on each element.
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*/
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call_rcu_tasks_trace(&c->rcu_ttrace, __free_rcu_tasks_trace);
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}
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static void free_bulk(struct bpf_mem_cache *c)
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{
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struct bpf_mem_cache *tgt = c->tgt;
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struct llist_node *llnode, *t;
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unsigned long flags;
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int cnt;
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WARN_ON_ONCE(tgt->unit_size != c->unit_size);
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WARN_ON_ONCE(tgt->percpu_size != c->percpu_size);
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do {
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inc_active(c, &flags);
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llnode = __llist_del_first(&c->free_llist);
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if (llnode)
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cnt = --c->free_cnt;
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else
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cnt = 0;
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dec_active(c, &flags);
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if (llnode)
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enque_to_free(tgt, llnode);
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} while (cnt > (c->high_watermark + c->low_watermark) / 2);
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/* and drain free_llist_extra */
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llist_for_each_safe(llnode, t, llist_del_all(&c->free_llist_extra))
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enque_to_free(tgt, llnode);
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do_call_rcu_ttrace(tgt);
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}
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static void __free_by_rcu(struct rcu_head *head)
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{
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struct bpf_mem_cache *c = container_of(head, struct bpf_mem_cache, rcu);
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struct bpf_mem_cache *tgt = c->tgt;
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struct llist_node *llnode;
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WARN_ON_ONCE(tgt->unit_size != c->unit_size);
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WARN_ON_ONCE(tgt->percpu_size != c->percpu_size);
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llnode = llist_del_all(&c->waiting_for_gp);
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if (!llnode)
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goto out;
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llist_add_batch(llnode, c->waiting_for_gp_tail, &tgt->free_by_rcu_ttrace);
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/* Objects went through regular RCU GP. Send them to RCU tasks trace */
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do_call_rcu_ttrace(tgt);
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out:
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atomic_set(&c->call_rcu_in_progress, 0);
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}
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static void check_free_by_rcu(struct bpf_mem_cache *c)
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{
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struct llist_node *llnode, *t;
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unsigned long flags;
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/* drain free_llist_extra_rcu */
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if (unlikely(!llist_empty(&c->free_llist_extra_rcu))) {
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inc_active(c, &flags);
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llist_for_each_safe(llnode, t, llist_del_all(&c->free_llist_extra_rcu))
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if (__llist_add(llnode, &c->free_by_rcu))
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c->free_by_rcu_tail = llnode;
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dec_active(c, &flags);
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}
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if (llist_empty(&c->free_by_rcu))
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return;
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if (atomic_xchg(&c->call_rcu_in_progress, 1)) {
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/*
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* Instead of kmalloc-ing new rcu_head and triggering 10k
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* call_rcu() to hit rcutree.qhimark and force RCU to notice
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* the overload just ask RCU to hurry up. There could be many
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* objects in free_by_rcu list.
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* This hint reduces memory consumption for an artificial
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* benchmark from 2 Gbyte to 150 Mbyte.
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*/
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rcu_request_urgent_qs_task(current);
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return;
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}
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WARN_ON_ONCE(!llist_empty(&c->waiting_for_gp));
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inc_active(c, &flags);
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WRITE_ONCE(c->waiting_for_gp.first, __llist_del_all(&c->free_by_rcu));
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c->waiting_for_gp_tail = c->free_by_rcu_tail;
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dec_active(c, &flags);
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if (unlikely(READ_ONCE(c->draining))) {
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free_all(llist_del_all(&c->waiting_for_gp), !!c->percpu_size);
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atomic_set(&c->call_rcu_in_progress, 0);
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} else {
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call_rcu_hurry(&c->rcu, __free_by_rcu);
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}
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}
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static void bpf_mem_refill(struct irq_work *work)
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{
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struct bpf_mem_cache *c = container_of(work, struct bpf_mem_cache, refill_work);
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int cnt;
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/* Racy access to free_cnt. It doesn't need to be 100% accurate */
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cnt = c->free_cnt;
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if (cnt < c->low_watermark)
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/* irq_work runs on this cpu and kmalloc will allocate
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* from the current numa node which is what we want here.
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*/
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alloc_bulk(c, c->batch, NUMA_NO_NODE, true);
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else if (cnt > c->high_watermark)
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free_bulk(c);
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check_free_by_rcu(c);
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}
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static void notrace irq_work_raise(struct bpf_mem_cache *c)
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{
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irq_work_queue(&c->refill_work);
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}
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/* For typical bpf map case that uses bpf_mem_cache_alloc and single bucket
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* the freelist cache will be elem_size * 64 (or less) on each cpu.
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*
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* For bpf programs that don't have statically known allocation sizes and
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* assuming (low_mark + high_mark) / 2 as an average number of elements per
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* bucket and all buckets are used the total amount of memory in freelists
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* on each cpu will be:
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* 64*16 + 64*32 + 64*64 + 64*96 + 64*128 + 64*196 + 64*256 + 32*512 + 16*1024 + 8*2048 + 4*4096
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* == ~ 116 Kbyte using below heuristic.
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* Initialized, but unused bpf allocator (not bpf map specific one) will
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* consume ~ 11 Kbyte per cpu.
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* Typical case will be between 11K and 116K closer to 11K.
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* bpf progs can and should share bpf_mem_cache when possible.
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*
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* 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, __percpu *pcc;
|
|
struct bpf_mem_cache *c, __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_KMEM
|
|
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_KMEM
|
|
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, __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);
|
|
}
|
|
if (ma->objcg)
|
|
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);
|
|
}
|
|
}
|
|
if (ma->objcg)
|
|
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;
|
|
}
|