From b936ca643ade11f265fa10e5fb71c20d9c5243f1 Mon Sep 17 00:00:00 2001
From: Roman Gushchin <guro@fb.com>
Date: Wed, 29 May 2019 18:03:58 -0700
Subject: bpf: rework memlock-based memory accounting for maps
In order to unify the existing memlock charging code with the
memcg-based memory accounting, which will be added later, let's
rework the current scheme.
Currently the following design is used:
1) .alloc() callback optionally checks if the allocation will likely
succeed using bpf_map_precharge_memlock()
2) .alloc() performs actual allocations
3) .alloc() callback calculates map cost and sets map.memory.pages
4) map_create() calls bpf_map_init_memlock() which sets map.memory.user
and performs actual charging; in case of failure the map is
destroyed
<map is in use>
1) bpf_map_free_deferred() calls bpf_map_release_memlock(), which
performs uncharge and releases the user
2) .map_free() callback releases the memory
The scheme can be simplified and made more robust:
1) .alloc() calculates map cost and calls bpf_map_charge_init()
2) bpf_map_charge_init() sets map.memory.user and performs actual
charge
3) .alloc() performs actual allocations
<map is in use>
1) .map_free() callback releases the memory
2) bpf_map_charge_finish() performs uncharge and releases the user
The new scheme also allows to reuse bpf_map_charge_init()/finish()
functions for memcg-based accounting. Because charges are performed
before actual allocations and uncharges after freeing the memory,
no bogus memory pressure can be created.
In cases when the map structure is not available (e.g. it's not
created yet, or is already destroyed), on-stack bpf_map_memory
structure is used. The charge can be transferred with the
bpf_map_charge_move() function.
Signed-off-by: Roman Gushchin <guro@fb.com>
Acked-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
---
kernel/bpf/queue_stack_maps.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)
(limited to 'kernel/bpf/queue_stack_maps.c')
diff --git a/kernel/bpf/queue_stack_maps.c b/kernel/bpf/queue_stack_maps.c
index 8a510e71d486..224cb0fd8f03 100644
--- a/kernel/bpf/queue_stack_maps.c
+++ b/kernel/bpf/queue_stack_maps.c
@@ -67,6 +67,7 @@ static int queue_stack_map_alloc_check(union bpf_attr *attr)
static struct bpf_map *queue_stack_map_alloc(union bpf_attr *attr)
{
int ret, numa_node = bpf_map_attr_numa_node(attr);
+ struct bpf_map_memory mem = {0};
struct bpf_queue_stack *qs;
u64 size, queue_size, cost;
@@ -77,19 +78,21 @@ static struct bpf_map *queue_stack_map_alloc(union bpf_attr *attr)
cost = round_up(cost, PAGE_SIZE) >> PAGE_SHIFT;
- ret = bpf_map_precharge_memlock(cost);
+ ret = bpf_map_charge_init(&mem, cost);
if (ret < 0)
return ERR_PTR(ret);
qs = bpf_map_area_alloc(queue_size, numa_node);
- if (!qs)
+ if (!qs) {
+ bpf_map_charge_finish(&mem);
return ERR_PTR(-ENOMEM);
+ }
memset(qs, 0, sizeof(*qs));
bpf_map_init_from_attr(&qs->map, attr);
- qs->map.memory.pages = cost;
+ bpf_map_charge_move(&qs->map.memory, &mem);
qs->size = size;
raw_spin_lock_init(&qs->lock);
--
cgit v1.2.3