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[2.42.195.208]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-a89891d86b5sm587968266b.178.2024.09.02.10.03.56 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 02 Sep 2024 10:03:57 -0700 (PDT) Date: Mon, 2 Sep 2024 19:03:55 +0200 From: Joe Damato To: Eric Dumazet Cc: netdev@vger.kernel.org, mkarsten@uwaterloo.ca, stable@kernel.org, Jakub Kicinski , "David S. Miller" , Paolo Abeni , Jonathan Corbet , Breno Leitao , Johannes Berg , Heiner Kallweit , Alexander Lobakin , "open list:DOCUMENTATION" , open list Subject: Re: [PATCH net] net: napi: Make napi_defer_irqs u32 Message-ID: Mail-Followup-To: Joe Damato , Eric Dumazet , netdev@vger.kernel.org, mkarsten@uwaterloo.ca, stable@kernel.org, Jakub Kicinski , "David S. Miller" , Paolo Abeni , Jonathan Corbet , Breno Leitao , Johannes Berg , Heiner Kallweit , Alexander Lobakin , "open list:DOCUMENTATION" , open list References: <20240831113223.9627-1-jdamato@fastly.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On Mon, Sep 02, 2024 at 03:01:28PM +0200, Eric Dumazet wrote: > On Sat, Aug 31, 2024 at 1:32 PM Joe Damato wrote: > > > > In commit 6f8b12d661d0 ("net: napi: add hard irqs deferral feature") > > napi_defer_irqs was added to net_device and napi_defer_irqs_count was > > added to napi_struct, both as type int. > > > > This value never goes below zero. Change the type for both from int to > > u32, and add an overflow check to sysfs to limit the value to S32_MAX. > > > > Before this patch: > > > > $ sudo bash -c 'echo 2147483649 > /sys/class/net/eth4/napi_defer_hard_irqs' > > $ cat /sys/class/net/eth4/napi_defer_hard_irqs > > -2147483647 > > > > After this patch: > > > > $ sudo bash -c 'echo 2147483649 > /sys/class/net/eth4/napi_defer_hard_irqs' > > bash: line 0: echo: write error: Numerical result out of range > > > > Fixes: 6f8b12d661d0 ("net: napi: add hard irqs deferral feature") > > Cc: stable@kernel.org > > Cc: Eric Dumazet > > Suggested-by: Jakub Kicinski > > Signed-off-by: Joe Damato > > --- > > I do not think this deserves a change to stable trees. > > Signed or unsigned, what is the issue ? > > Do you really need one extra bit ? > > /sys/class/net/XXXXX/tx_queue_len has a similar behavior. Sorry, Eric, I'm not following. Are you asking me to allow u32_max for napi_defer_hard_irqs the same way tx_queue_len does and avoid overflow that way: include/linux/netdevice.h: unsigned int tx_queue_len; dev_change_tx_queue_len(..., unsigned long new_len): if (new_len != (unsigned int)new_len) return -ERANGE;