From mboxrd@z Thu Jan 1 00:00:00 1970 From: Roman Gushchin Subject: Re: [PATCH v3 bpf-next 03/10] bpf: introduce per-cpu cgroup local storage Date: Fri, 28 Sep 2018 11:03:03 +0100 Message-ID: <20180928100302.GB9018@castle.DHCP.thefacebook.com> References: <20180926113326.29069-1-guro@fb.com> <20180926113326.29069-4-guro@fb.com> <20180928084528.i5txkac34pmqvs3p@ast-mbp.dhcp.thefacebook.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Cc: , Song Liu , , , Daniel Borkmann , Alexei Starovoitov To: Alexei Starovoitov Return-path: Content-Disposition: inline In-Reply-To: <20180928084528.i5txkac34pmqvs3p@ast-mbp.dhcp.thefacebook.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Fri, Sep 28, 2018 at 10:45:31AM +0200, Alexei Starovoitov wrote: > On Wed, Sep 26, 2018 at 12:33:19PM +0100, Roman Gushchin wrote: > > This commit introduced per-cpu cgroup local storage. > > > > Per-cpu cgroup local storage is very similar to simple cgroup storage > > (let's call it shared), except all the data is per-cpu. > > > > The main goal of per-cpu variant is to implement super fast > > counters (e.g. packet counters), which don't require neither > > lookups, neither atomic operations. > > > > From userspace's point of view, accessing a per-cpu cgroup storage > > is similar to other per-cpu map types (e.g. per-cpu hashmaps and > > arrays). > > > > Writing to a per-cpu cgroup storage is not atomic, but is performed > > by copying longs, so some minimal atomicity is here, exactly > > as with other per-cpu maps. > > > > Signed-off-by: Roman Gushchin > > Cc: Daniel Borkmann > > Cc: Alexei Starovoitov > > --- > > include/linux/bpf-cgroup.h | 20 ++++- > > include/linux/bpf.h | 1 + > > include/linux/bpf_types.h | 1 + > > include/uapi/linux/bpf.h | 1 + > > kernel/bpf/helpers.c | 8 +- > > kernel/bpf/local_storage.c | 148 ++++++++++++++++++++++++++++++++----- > > kernel/bpf/syscall.c | 11 ++- > > kernel/bpf/verifier.c | 15 +++- > > 8 files changed, 177 insertions(+), 28 deletions(-) > > > > diff --git a/include/linux/bpf-cgroup.h b/include/linux/bpf-cgroup.h > > index 7e0c9a1d48b7..588dd5f0bd85 100644 > > --- a/include/linux/bpf-cgroup.h > > +++ b/include/linux/bpf-cgroup.h > > @@ -37,7 +37,10 @@ struct bpf_storage_buffer { > > }; > > > > struct bpf_cgroup_storage { > > - struct bpf_storage_buffer *buf; > > + union { > > + struct bpf_storage_buffer *buf; > > + void __percpu *percpu_buf; > > + }; > > struct bpf_cgroup_storage_map *map; > > struct bpf_cgroup_storage_key key; > > struct list_head list; > > @@ -109,6 +112,9 @@ int __cgroup_bpf_check_dev_permission(short dev_type, u32 major, u32 minor, > > static inline enum bpf_cgroup_storage_type cgroup_storage_type( > > struct bpf_map *map) > > { > > + if (map->map_type == BPF_MAP_TYPE_PERCPU_CGROUP_STORAGE) > > + return BPF_CGROUP_STORAGE_PERCPU; > > + > > return BPF_CGROUP_STORAGE_SHARED; > > } > > > > @@ -131,6 +137,10 @@ void bpf_cgroup_storage_unlink(struct bpf_cgroup_storage *storage); > > int bpf_cgroup_storage_assign(struct bpf_prog *prog, struct bpf_map *map); > > void bpf_cgroup_storage_release(struct bpf_prog *prog, struct bpf_map *map); > > > > +int bpf_percpu_cgroup_storage_copy(struct bpf_map *map, void *key, void *value); > > +int bpf_percpu_cgroup_storage_update(struct bpf_map *map, void *key, > > + void *value, u64 flags); > > + > > /* Wrappers for __cgroup_bpf_run_filter_skb() guarded by cgroup_bpf_enabled. */ > > #define BPF_CGROUP_RUN_PROG_INET_INGRESS(sk, skb) \ > > ({ \ > > @@ -285,6 +295,14 @@ static inline struct bpf_cgroup_storage *bpf_cgroup_storage_alloc( > > struct bpf_prog *prog, enum bpf_cgroup_storage_type stype) { return 0; } > > static inline void bpf_cgroup_storage_free( > > struct bpf_cgroup_storage *storage) {} > > +static inline int bpf_percpu_cgroup_storage_copy(struct bpf_map *map, void *key, > > + void *value) { > > + return 0; > > +} > > +static inline int bpf_percpu_cgroup_storage_update(struct bpf_map *map, > > + void *key, void *value, u64 flags) { > > + return 0; > > +} > > > > #define cgroup_bpf_enabled (0) > > #define BPF_CGROUP_PRE_CONNECT_ENABLED(sk) (0) > > diff --git a/include/linux/bpf.h b/include/linux/bpf.h > > index b457fbe7b70b..018299a595c8 100644 > > --- a/include/linux/bpf.h > > +++ b/include/linux/bpf.h > > @@ -274,6 +274,7 @@ struct bpf_prog_offload { > > > > enum bpf_cgroup_storage_type { > > BPF_CGROUP_STORAGE_SHARED, > > + BPF_CGROUP_STORAGE_PERCPU, > > __BPF_CGROUP_STORAGE_MAX > > }; > > > > diff --git a/include/linux/bpf_types.h b/include/linux/bpf_types.h > > index c9bd6fb765b0..5432f4c9f50e 100644 > > --- a/include/linux/bpf_types.h > > +++ b/include/linux/bpf_types.h > > @@ -43,6 +43,7 @@ BPF_MAP_TYPE(BPF_MAP_TYPE_CGROUP_ARRAY, cgroup_array_map_ops) > > #endif > > #ifdef CONFIG_CGROUP_BPF > > BPF_MAP_TYPE(BPF_MAP_TYPE_CGROUP_STORAGE, cgroup_storage_map_ops) > > +BPF_MAP_TYPE(BPF_MAP_TYPE_PERCPU_CGROUP_STORAGE, cgroup_storage_map_ops) > > #endif > > BPF_MAP_TYPE(BPF_MAP_TYPE_HASH, htab_map_ops) > > BPF_MAP_TYPE(BPF_MAP_TYPE_PERCPU_HASH, htab_percpu_map_ops) > > diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h > > index aa5ccd2385ed..e2070d819e04 100644 > > --- a/include/uapi/linux/bpf.h > > +++ b/include/uapi/linux/bpf.h > > @@ -127,6 +127,7 @@ enum bpf_map_type { > > BPF_MAP_TYPE_SOCKHASH, > > BPF_MAP_TYPE_CGROUP_STORAGE, > > BPF_MAP_TYPE_REUSEPORT_SOCKARRAY, > > + BPF_MAP_TYPE_PERCPU_CGROUP_STORAGE, > > }; > > > > enum bpf_prog_type { > > diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c > > index e42f8789b7ea..6502115e8f55 100644 > > --- a/kernel/bpf/helpers.c > > +++ b/kernel/bpf/helpers.c > > @@ -206,10 +206,16 @@ BPF_CALL_2(bpf_get_local_storage, struct bpf_map *, map, u64, flags) > > */ > > enum bpf_cgroup_storage_type stype = cgroup_storage_type(map); > > struct bpf_cgroup_storage *storage; > > + void *ptr; > > > > storage = this_cpu_read(bpf_cgroup_storage[stype]); > > > > - return (unsigned long)&READ_ONCE(storage->buf)->data[0]; > > + if (stype == BPF_CGROUP_STORAGE_SHARED) > > + ptr = &READ_ONCE(storage->buf)->data[0]; > > + else > > + ptr = this_cpu_ptr(storage->percpu_buf); > > + > > + return (unsigned long)ptr; > > } > > > > const struct bpf_func_proto bpf_get_local_storage_proto = { > > diff --git a/kernel/bpf/local_storage.c b/kernel/bpf/local_storage.c > > index 6742292fb39e..c739f6dcc3c2 100644 > > --- a/kernel/bpf/local_storage.c > > +++ b/kernel/bpf/local_storage.c > > @@ -152,6 +152,71 @@ static int cgroup_storage_update_elem(struct bpf_map *map, void *_key, > > return 0; > > } > > > > +int bpf_percpu_cgroup_storage_copy(struct bpf_map *_map, void *_key, > > + void *value) > > +{ > > + struct bpf_cgroup_storage_map *map = map_to_storage(_map); > > + struct bpf_cgroup_storage_key *key = _key; > > + struct bpf_cgroup_storage *storage; > > + int cpu, off = 0; > > + u32 size; > > + > > + rcu_read_lock(); > > + storage = cgroup_storage_lookup(map, key, false); > > + if (!storage) { > > + rcu_read_unlock(); > > + return -ENOENT; > > + } > > + > > + /* per_cpu areas are zero-filled and bpf programs can only > > + * access 'value_size' of them, so copying rounded areas > > + * will not leak any kernel data > > + */ > > + size = round_up(_map->value_size, 8); > > + for_each_possible_cpu(cpu) { > > + bpf_long_memcpy(value + off, > > + per_cpu_ptr(storage->percpu_buf, cpu), size); > > + off += size; > > + } > > + rcu_read_unlock(); > > + return 0; > > +} > > + > > +int bpf_percpu_cgroup_storage_update(struct bpf_map *_map, void *_key, > > + void *value, u64 map_flags) > > +{ > > + struct bpf_cgroup_storage_map *map = map_to_storage(_map); > > + struct bpf_cgroup_storage_key *key = _key; > > + struct bpf_cgroup_storage *storage; > > + int cpu, off = 0; > > + u32 size; > > + > > + if (unlikely(map_flags & BPF_EXIST)) > > + return -EINVAL; > > that should have been BPF_NOEXIST ? Yeah, or maybe even better s/&/!= ? It's probably better to require BPF_EXIST flag to update a cgroup storage? Agree? If so, let me fix this for both shared and per-cpu versions in a follow-up patch. > > > + > > + rcu_read_lock(); > > + storage = cgroup_storage_lookup(map, key, false); > > + if (!storage) { > > + rcu_read_unlock(); > > + return -ENOENT; > > + } > > + > > + /* the user space will provide round_up(value_size, 8) bytes that > > + * will be copied into per-cpu area. bpf programs can only access > > + * value_size of it. During lookup the same extra bytes will be > > + * returned or zeros which were zero-filled by percpu_alloc, > > + * so no kernel data leaks possible > > + */ > > + size = round_up(_map->value_size, 8); > > + for_each_possible_cpu(cpu) { > > + bpf_long_memcpy(per_cpu_ptr(storage->percpu_buf, cpu), > > + value + off, size); > > + off += size; > > + } > > + rcu_read_unlock(); > > storage_update and storage_copy look essentially the same > with the only difference that src/dst swap. > Would it be possible to combine them ? > Not sure whether #define template would look better. I'll try to refactor this and next one in a follow-up patch. Thanks!