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[2.104.116.184]) by smtp.gmail.com with ESMTPSA id a26-20020a19f81a000000b0047255d21116sm2611832lff.69.2022.05.24.09.21.02 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 24 May 2022 09:21:03 -0700 (PDT) From: Hans Schultz X-Google-Original-From: Hans Schultz To: Nikolay Aleksandrov , Hans Schultz , davem@davemloft.net, kuba@kernel.org Cc: netdev@vger.kernel.org, Andrew Lunn , Vivien Didelot , Florian Fainelli , Vladimir Oltean , Eric Dumazet , Paolo Abeni , Jiri Pirko , Ivan Vecera , Roopa Prabhu , Shuah Khan , Daniel Borkmann , Ido Schimmel , linux-kernel@vger.kernel.org, bridge@lists.linux-foundation.org, linux-kselftest@vger.kernel.org Subject: Re: [PATCH V3 net-next 1/4] net: bridge: add fdb flag to extent locked port feature In-Reply-To: <01e6e35c-f5c9-9776-1263-058f84014ed9@blackwall.org> References: <20220524152144.40527-1-schultz.hans+netdev@gmail.com> <20220524152144.40527-2-schultz.hans+netdev@gmail.com> <01e6e35c-f5c9-9776-1263-058f84014ed9@blackwall.org> Date: Tue, 24 May 2022 18:21:02 +0200 Message-ID: <86zgj6oqa9.fsf@gmail.com> MIME-Version: 1.0 Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > > Hi Hans, > So this approach has a fundamental problem, f->dst is changed without any synchronization > you cannot rely on it and thus you cannot account for these entries properly. We must be very > careful if we try to add any new synchronization not to affect performance as well. > More below... > >> @@ -319,6 +326,9 @@ static void fdb_delete(struct net_bridge *br, struct net_bridge_fdb_entry *f, >> if (test_bit(BR_FDB_STATIC, &f->flags)) >> fdb_del_hw_addr(br, f->key.addr.addr); >> >> + if (test_bit(BR_FDB_ENTRY_LOCKED, &f->flags) && !test_bit(BR_FDB_OFFLOADED, &f->flags)) >> + atomic_dec(&f->dst->locked_entry_cnt); > > Sorry but you cannot do this for multiple reasons: > - f->dst can be NULL > - f->dst changes without any synchronization > - there is no synchronization between fdb's flags and its ->dst > > Cheers, > Nik Hi Nik, if a port is decoupled from the bridge, the locked entries would of course be invalid, so maybe if adding and removing a port is accounted for wrt locked entries and the count of locked entries, would that not work? Best, Hans From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=from:to:cc:subject:in-reply-to:references:date:message-id :mime-version; bh=2/bDGPYXufJFzkVnBY8mqDgAglNZetlk8WJ7Djt/e2E=; b=e6JB8CI6WFSU+Q/ABVHaxlfYhBRAsmmbmkIDuhn1m6DKPOXKF37gjB/m9GdsVi49dc JNf43jPT5zw03LMoVZ8t3fuV30/a2V5p20h02AkSpplyqHBCbbU0BEhybKuk9LvBIU0v yF5u5B3igHgLN7iRG8ZQrDAszFgPNI/I5CRCOoGPWgb0Tr5z/PCYQqsyZhaq45tfM2ue TR82sVYgQfPiZLzURg9Q0Ng/5eocdGR5EPE8FxukEwr6LoxzCf3TXITUf9yHbYMLAfmG vt/o3bafEdXjgzQsP4rsUwQGadPuBcmEHO5dtLS97SrWhTOdZeC4FS/jt5IR6+lcfUJ1 OuKg== From: Hans Schultz In-Reply-To: <01e6e35c-f5c9-9776-1263-058f84014ed9@blackwall.org> References: <20220524152144.40527-1-schultz.hans+netdev@gmail.com> <20220524152144.40527-2-schultz.hans+netdev@gmail.com> <01e6e35c-f5c9-9776-1263-058f84014ed9@blackwall.org> Date: Tue, 24 May 2022 18:21:02 +0200 Message-ID: <86zgj6oqa9.fsf@gmail.com> MIME-Version: 1.0 Content-Type: text/plain Subject: Re: [Bridge] [PATCH V3 net-next 1/4] net: bridge: add fdb flag to extent locked port feature List-Id: Linux Ethernet Bridging List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Nikolay Aleksandrov , Hans Schultz , davem@davemloft.net, kuba@kernel.org Cc: Ivan Vecera , Andrew Lunn , Florian Fainelli , Jiri Pirko , Daniel Borkmann , netdev@vger.kernel.org, Ido Schimmel , bridge@lists.linux-foundation.org, linux-kernel@vger.kernel.org, Eric Dumazet , linux-kselftest@vger.kernel.org, Roopa Prabhu , Paolo Abeni , Vladimir Oltean , Shuah Khan , Vivien Didelot > > Hi Hans, > So this approach has a fundamental problem, f->dst is changed without any synchronization > you cannot rely on it and thus you cannot account for these entries properly. We must be very > careful if we try to add any new synchronization not to affect performance as well. > More below... > >> @@ -319,6 +326,9 @@ static void fdb_delete(struct net_bridge *br, struct net_bridge_fdb_entry *f, >> if (test_bit(BR_FDB_STATIC, &f->flags)) >> fdb_del_hw_addr(br, f->key.addr.addr); >> >> + if (test_bit(BR_FDB_ENTRY_LOCKED, &f->flags) && !test_bit(BR_FDB_OFFLOADED, &f->flags)) >> + atomic_dec(&f->dst->locked_entry_cnt); > > Sorry but you cannot do this for multiple reasons: > - f->dst can be NULL > - f->dst changes without any synchronization > - there is no synchronization between fdb's flags and its ->dst > > Cheers, > Nik Hi Nik, if a port is decoupled from the bridge, the locked entries would of course be invalid, so maybe if adding and removing a port is accounted for wrt locked entries and the count of locked entries, would that not work? Best, Hans