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Wed, 28 May 2025 17:04:10 -0700 (PDT) Received: from gmail.com ([98.97.34.246]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-23506bc86c2sm1587855ad.43.2025.05.28.17.04.09 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 28 May 2025 17:04:10 -0700 (PDT) Date: Wed, 28 May 2025 17:04:05 -0700 From: John Fastabend To: Cong Wang Cc: netdev@vger.kernel.org, bpf@vger.kernel.org, zhoufeng.zf@bytedance.com, jakub@cloudflare.com, zijianzhang@bytedance.com, Cong Wang Subject: Re: [Patch bpf-next v3 2/4] skmsg: implement slab allocator cache for sk_msg Message-ID: <20250529000348.upto3ztve36ccamv@gmail.com> References: <20250519203628.203596-1-xiyou.wangcong@gmail.com> <20250519203628.203596-3-xiyou.wangcong@gmail.com> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250519203628.203596-3-xiyou.wangcong@gmail.com> On 2025-05-19 13:36:26, Cong Wang wrote: > From: Zijian Zhang > > Optimizing redirect ingress performance requires frequent allocation and > deallocation of sk_msg structures. Introduce a dedicated kmem_cache for > sk_msg to reduce memory allocation overhead and improve performance. > > Reviewed-by: Cong Wang > Signed-off-by: Zijian Zhang > --- > include/linux/skmsg.h | 21 ++++++++++++--------- > net/core/skmsg.c | 28 +++++++++++++++++++++------- > net/ipv4/tcp_bpf.c | 5 ++--- > 3 files changed, 35 insertions(+), 19 deletions(-) > > diff --git a/include/linux/skmsg.h b/include/linux/skmsg.h > index d6f0a8cd73c4..bf28ce9b5fdb 100644 > --- a/include/linux/skmsg.h > +++ b/include/linux/skmsg.h > @@ -121,6 +121,7 @@ struct sk_psock { > struct rcu_work rwork; > }; > > +struct sk_msg *sk_msg_alloc(gfp_t gfp); > int sk_msg_expand(struct sock *sk, struct sk_msg *msg, int len, > int elem_first_coalesce); > int sk_msg_clone(struct sock *sk, struct sk_msg *dst, struct sk_msg *src, > @@ -143,6 +144,8 @@ int sk_msg_recvmsg(struct sock *sk, struct sk_psock *psock, struct msghdr *msg, > int len, int flags); > bool sk_msg_is_readable(struct sock *sk); > > +extern struct kmem_cache *sk_msg_cachep; > + > static inline void sk_msg_check_to_free(struct sk_msg *msg, u32 i, u32 bytes) > { > WARN_ON(i == msg->sg.end && bytes); > @@ -319,6 +322,13 @@ static inline void sock_drop(struct sock *sk, struct sk_buff *skb) > kfree_skb(skb); > } > > +static inline void kfree_sk_msg(struct sk_msg *msg) > +{ > + if (msg->skb) > + consume_skb(msg->skb); > + kmem_cache_free(sk_msg_cachep, msg); > +} > + > static inline bool sk_psock_queue_msg(struct sk_psock *psock, > struct sk_msg *msg) > { > @@ -330,7 +340,7 @@ static inline bool sk_psock_queue_msg(struct sk_psock *psock, > ret = true; > } else { > sk_msg_free(psock->sk, msg); > - kfree(msg); > + kfree_sk_msg(msg); Isn't this a potential use after free on msg->skb? The sk_msg_free() a line above will consume_skb() if it exists and its not nil set so we would consume_skb() again? > ret = false; > } > spin_unlock_bh(&psock->ingress_lock); > @@ -378,13 +388,6 @@ static inline bool sk_psock_queue_empty(const struct sk_psock *psock) > return psock ? list_empty(&psock->ingress_msg) : true; > } > > -static inline void kfree_sk_msg(struct sk_msg *msg) > -{ > - if (msg->skb) > - consume_skb(msg->skb); > - kfree(msg); > -} > - > static inline void sk_psock_report_error(struct sk_psock *psock, int err) > { > struct sock *sk = psock->sk; > @@ -441,7 +444,7 @@ static inline void sk_psock_cork_free(struct sk_psock *psock) > { > if (psock->cork) { > sk_msg_free(psock->sk, psock->cork); > - kfree(psock->cork); > + kfree_sk_msg(psock->cork); Same here. > psock->cork = NULL; > } > }