[PATCH v6 27/34] bpf: eliminate rlimit-based memory accounting for bpf ringbuffer

[Roman Gushchin]

Do not use rlimit-based memory accounting for bpf ringbuffer.
It has been replaced with the memcg-based memory accounting.

bpf_ringbuf_alloc() can't return anything except ERR_PTR(-ENOMEM)
and a valid pointer, so to simplify the code make it return NULL
in the first case. This allows to drop a couple of lines in
ringbuf_map_alloc() and also makes it look similar to other memory
allocating function like kmalloc().

Signed-off-by: Roman Gushchin <guro@xxxxxx>
Acked-by: Song Liu <songliubraving@xxxxxx>
Acked-by: Andrii Nakryiko <andriin@xxxxxx>
---
 kernel/bpf/ringbuf.c | 24 ++++--------------------
 1 file changed, 4 insertions(+), 20 deletions(-)

diff --git a/kernel/bpf/ringbuf.c b/kernel/bpf/ringbuf.c
index ee5f55d9276e..c8892b58501e 100644
--- a/kernel/bpf/ringbuf.c
+++ b/kernel/bpf/ringbuf.c
@@ -48,7 +48,6 @@ struct bpf_ringbuf {
 
 struct bpf_ringbuf_map {
 	struct bpf_map map;
-	struct bpf_map_memory memory;
 	struct bpf_ringbuf *rb;
 };
 
@@ -135,7 +134,7 @@ static struct bpf_ringbuf *bpf_ringbuf_alloc(size_t data_sz, int numa_node)
 
 	rb = bpf_ringbuf_area_alloc(data_sz, numa_node);
 	if (!rb)
-		return ERR_PTR(-ENOMEM);
+		return NULL;
 
 	spin_lock_init(&rb->spinlock);
 	init_waitqueue_head(&rb->waitq);
@@ -151,8 +150,6 @@ static struct bpf_ringbuf *bpf_ringbuf_alloc(size_t data_sz, int numa_node)
 static struct bpf_map *ringbuf_map_alloc(union bpf_attr *attr)
 {
 	struct bpf_ringbuf_map *rb_map;
-	u64 cost;
-	int err;
 
 	if (attr->map_flags & ~RINGBUF_CREATE_FLAG_MASK)
 		return ERR_PTR(-EINVAL);
@@ -174,26 +171,13 @@ static struct bpf_map *ringbuf_map_alloc(union bpf_attr *attr)
 
 	bpf_map_init_from_attr(&rb_map->map, attr);
 
-	cost = sizeof(struct bpf_ringbuf_map) +
-	       sizeof(struct bpf_ringbuf) +
-	       attr->max_entries;
-	err = bpf_map_charge_init(&rb_map->map.memory, cost);
-	if (err)
-		goto err_free_map;
-
 	rb_map->rb = bpf_ringbuf_alloc(attr->max_entries, rb_map->map.numa_node);
-	if (IS_ERR(rb_map->rb)) {
-		err = PTR_ERR(rb_map->rb);
-		goto err_uncharge;
+	if (!rb_map->rb) {
+		kfree(rb_map);
+		return ERR_PTR(-ENOMEM);
 	}
 
 	return &rb_map->map;
-
-err_uncharge:
-	bpf_map_charge_finish(&rb_map->map.memory);
-err_free_map:
-	kfree(rb_map);
-	return ERR_PTR(err);
 }
 
 static void bpf_ringbuf_free(struct bpf_ringbuf *rb)
-- 
2.26.2