kernel/bpf/bpf_local_storage.c

286 		 * read if the freeing of the storage is done
290 		 * to the caller which then calls then frees the storage after
453 	struct bpf_local_storage *prev_storage, *storage;
457 	err = mem_charge(smap, owner, sizeof(*storage));
463 		storage = bpf_mem_cache_alloc_flags(&smap->storage_ma, gfp_flags);
466 		storage = bpf_map_kzalloc(&smap->map, sizeof(*storage),
470 	if (!storage) {
475 	RCU_INIT_POINTER(storage->smap, smap);
476 	INIT_HLIST_HEAD(&storage->list);
477 	raw_spin_lock_init(&storage->lock);
478 	storage->owner = owner;
480 	bpf_selem_link_storage_nolock(storage, first_selem);
485 	/* Publish storage to the owner.
490 	 * From now on, the owner->storage pointer (e.g. sk->sk_bpf_storage)
491 	 * is protected by the storage->lock.  Hence, when freeing
492 	 * the owner->storage, the storage->lock must be held before
493 	 * setting owner->storage ptr to NULL.
495 	prev_storage = cmpxchg(owner_storage_ptr, NULL, storage);
515 	bpf_local_storage_free(storage, smap, smap->bpf_ma, true);
516 	mem_uncharge(smap, owner, sizeof(*storage));
733 		 * intends to remove all local storage. So the last iteration
756  * A deadlock free allocator is useful for storage that the bpf prog can easily
758  * The task and cgroup storage fall into this case. The bpf_mem_alloc reuses
843 	 * to the owner->storage or to the map bucket's list.
846 	 * or when the storage is freed e.g.
871 	/* While freeing the storage we may still need to access the map.
877 	 * However, while freeing the storage one still needs to access the
881 	 * Hence, wait another rcu grace period for the storage to be freed.