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Miller" , Jakub Kicinski , Paolo Abeni , netdev@vger.kernel.org, eric.dumazet@gmail.com Subject: Re: [PATCH net-next 12/13] rtnetlink: make rtnl_fill_link_ifmap() RCU ready Message-ID: References: <20240221105915.829140-1-edumazet@google.com> <20240221105915.829140-13-edumazet@google.com> Precedence: bulk X-Mailing-List: netdev@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: Wed, Feb 21, 2024 at 06:15:11PM CET, edumazet@google.com wrote: >On Wed, Feb 21, 2024 at 5:03 PM Jiri Pirko wrote: >> >> Wed, Feb 21, 2024 at 11:59:14AM CET, edumazet@google.com wrote: >> >Use READ_ONCE() to read the following device fields: >> > >> > dev->mem_start >> > dev->mem_end >> > dev->base_addr >> > dev->irq >> > dev->dma >> > dev->if_port >> > >> >Provide IFLA_MAP attribute only if at least one of these fields >> >is not zero. This saves some space in the output skb for most devices. >> > >> >Signed-off-by: Eric Dumazet >> >--- >> > net/core/rtnetlink.c | 26 ++++++++++++++------------ >> > 1 file changed, 14 insertions(+), 12 deletions(-) >> > >> >diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c >> >index 1b26dfa5668d22fb2e30ceefbf143e98df13ae29..b91ec216c593aaebf97ea69aa0d2d265ab61c098 100644 >> >--- a/net/core/rtnetlink.c >> >+++ b/net/core/rtnetlink.c >> >@@ -1455,19 +1455,21 @@ static noinline_for_stack int rtnl_fill_vf(struct sk_buff *skb, >> > return 0; >> > } >> > >> >-static int rtnl_fill_link_ifmap(struct sk_buff *skb, struct net_device *dev) >> >+static int rtnl_fill_link_ifmap(struct sk_buff *skb, >> >+ const struct net_device *dev) >> > { >> > struct rtnl_link_ifmap map; >> > >> > memset(&map, 0, sizeof(map)); >> >- map.mem_start = dev->mem_start; >> >- map.mem_end = dev->mem_end; >> >- map.base_addr = dev->base_addr; >> >- map.irq = dev->irq; >> >- map.dma = dev->dma; >> >- map.port = dev->if_port; >> >- >> >- if (nla_put_64bit(skb, IFLA_MAP, sizeof(map), &map, IFLA_PAD)) >> >+ map.mem_start = READ_ONCE(dev->mem_start); >> >+ map.mem_end = READ_ONCE(dev->mem_end); >> >+ map.base_addr = READ_ONCE(dev->base_addr); >> >+ map.irq = READ_ONCE(dev->irq); >> >+ map.dma = READ_ONCE(dev->dma); >> >+ map.port = READ_ONCE(dev->if_port); >> >+ /* Only report non zero information. */ >> >+ if (memchr_inv(&map, 0, sizeof(map)) && >> >> This check(optimization) is unrelated to the rest of the patch, correct? >> If yes, could it be a separate patch? > >Sure thing. BTW, do you know which tool is using this ? > >I could not find IFLA_MAP being used in iproute2 or ethtool. No clue. Never spotted it.