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Thu, 18 Dec 2025 09:56:38 -0800 (PST) Received: from localhost ([2a03:2880:ff:4a::]) by smtp.gmail.com with ESMTPSA id 41be03b00d2f7-c1d2fff94e5sm2889041a12.25.2025.12.18.09.56.38 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 18 Dec 2025 09:56:38 -0800 (PST) From: Amery Hung To: bpf@vger.kernel.org Cc: netdev@vger.kernel.org, alexei.starovoitov@gmail.com, andrii@kernel.org, daniel@iogearbox.net, memxor@gmail.com, martin.lau@kernel.org, kpsingh@kernel.org, yonghong.song@linux.dev, song@kernel.org, haoluo@google.com, ameryhung@gmail.com, kernel-team@meta.com Subject: [PATCH bpf-next v3 07/16] bpf: Remove cgroup local storage percpu counter Date: Thu, 18 Dec 2025 09:56:17 -0800 Message-ID: <20251218175628.1460321-8-ameryhung@gmail.com> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20251218175628.1460321-1-ameryhung@gmail.com> References: <20251218175628.1460321-1-ameryhung@gmail.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit The percpu counter in cgroup local storage is no longer needed as the underlying bpf_local_storage can now handle deadlock with the help of rqspinlock. Remove the percpu counter and related migrate_{disable, enable}. Signed-off-by: Amery Hung --- kernel/bpf/bpf_cgrp_storage.c | 59 +++++------------------------------ 1 file changed, 8 insertions(+), 51 deletions(-) diff --git a/kernel/bpf/bpf_cgrp_storage.c b/kernel/bpf/bpf_cgrp_storage.c index 8fef24fcac68..4d84611d8222 100644 --- a/kernel/bpf/bpf_cgrp_storage.c +++ b/kernel/bpf/bpf_cgrp_storage.c @@ -11,29 +11,6 @@ DEFINE_BPF_STORAGE_CACHE(cgroup_cache); -static DEFINE_PER_CPU(int, bpf_cgrp_storage_busy); - -static void bpf_cgrp_storage_lock(void) -{ - cant_migrate(); - this_cpu_inc(bpf_cgrp_storage_busy); -} - -static void bpf_cgrp_storage_unlock(void) -{ - this_cpu_dec(bpf_cgrp_storage_busy); -} - -static bool bpf_cgrp_storage_trylock(void) -{ - cant_migrate(); - if (unlikely(this_cpu_inc_return(bpf_cgrp_storage_busy) != 1)) { - this_cpu_dec(bpf_cgrp_storage_busy); - return false; - } - return true; -} - static struct bpf_local_storage __rcu **cgroup_storage_ptr(void *owner) { struct cgroup *cg = owner; @@ -45,16 +22,14 @@ void bpf_cgrp_storage_free(struct cgroup *cgroup) { struct bpf_local_storage *local_storage; - rcu_read_lock_dont_migrate(); + rcu_read_lock(); local_storage = rcu_dereference(cgroup->bpf_cgrp_storage); if (!local_storage) goto out; - bpf_cgrp_storage_lock(); bpf_local_storage_destroy(local_storage); - bpf_cgrp_storage_unlock(); out: - rcu_read_unlock_migrate(); + rcu_read_unlock(); } static struct bpf_local_storage_data * @@ -83,9 +58,7 @@ static void *bpf_cgrp_storage_lookup_elem(struct bpf_map *map, void *key) if (IS_ERR(cgroup)) return ERR_CAST(cgroup); - bpf_cgrp_storage_lock(); sdata = cgroup_storage_lookup(cgroup, map, true); - bpf_cgrp_storage_unlock(); cgroup_put(cgroup); return sdata ? sdata->data : NULL; } @@ -102,10 +75,8 @@ static long bpf_cgrp_storage_update_elem(struct bpf_map *map, void *key, if (IS_ERR(cgroup)) return PTR_ERR(cgroup); - bpf_cgrp_storage_lock(); sdata = bpf_local_storage_update(cgroup, (struct bpf_local_storage_map *)map, value, map_flags, false, GFP_ATOMIC); - bpf_cgrp_storage_unlock(); cgroup_put(cgroup); return PTR_ERR_OR_ZERO(sdata); } @@ -131,9 +102,7 @@ static long bpf_cgrp_storage_delete_elem(struct bpf_map *map, void *key) if (IS_ERR(cgroup)) return PTR_ERR(cgroup); - bpf_cgrp_storage_lock(); err = cgroup_storage_delete(cgroup, map); - bpf_cgrp_storage_unlock(); cgroup_put(cgroup); return err; } @@ -150,7 +119,7 @@ static struct bpf_map *cgroup_storage_map_alloc(union bpf_attr *attr) static void cgroup_storage_map_free(struct bpf_map *map) { - bpf_local_storage_map_free(map, &cgroup_cache, &bpf_cgrp_storage_busy); + bpf_local_storage_map_free(map, &cgroup_cache, NULL); } /* *gfp_flags* is a hidden argument provided by the verifier */ @@ -158,7 +127,6 @@ BPF_CALL_5(bpf_cgrp_storage_get, struct bpf_map *, map, struct cgroup *, cgroup, void *, value, u64, flags, gfp_t, gfp_flags) { struct bpf_local_storage_data *sdata; - bool nobusy; WARN_ON_ONCE(!bpf_rcu_lock_held()); if (flags & ~(BPF_LOCAL_STORAGE_GET_F_CREATE)) @@ -167,38 +135,27 @@ BPF_CALL_5(bpf_cgrp_storage_get, struct bpf_map *, map, struct cgroup *, cgroup, if (!cgroup) return (unsigned long)NULL; - nobusy = bpf_cgrp_storage_trylock(); - - sdata = cgroup_storage_lookup(cgroup, map, nobusy); + sdata = cgroup_storage_lookup(cgroup, map, true); if (sdata) - goto unlock; + goto out; /* only allocate new storage, when the cgroup is refcounted */ if (!percpu_ref_is_dying(&cgroup->self.refcnt) && - (flags & BPF_LOCAL_STORAGE_GET_F_CREATE) && nobusy) + (flags & BPF_LOCAL_STORAGE_GET_F_CREATE)) sdata = bpf_local_storage_update(cgroup, (struct bpf_local_storage_map *)map, value, BPF_NOEXIST, false, gfp_flags); -unlock: - if (nobusy) - bpf_cgrp_storage_unlock(); +out: return IS_ERR_OR_NULL(sdata) ? (unsigned long)NULL : (unsigned long)sdata->data; } BPF_CALL_2(bpf_cgrp_storage_delete, struct bpf_map *, map, struct cgroup *, cgroup) { - int ret; - WARN_ON_ONCE(!bpf_rcu_lock_held()); if (!cgroup) return -EINVAL; - if (!bpf_cgrp_storage_trylock()) - return -EBUSY; - - ret = cgroup_storage_delete(cgroup, map); - bpf_cgrp_storage_unlock(); - return ret; + return cgroup_storage_delete(cgroup, map); } const struct bpf_map_ops cgrp_storage_map_ops = { -- 2.47.3