From patchwork Wed Jan 15 03:53:12 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jakub Kicinski X-Patchwork-Id: 13939816 X-Patchwork-Delegate: kuba@kernel.org Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 53DFE22E41D for ; Wed, 15 Jan 2025 03:53:39 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1736913219; cv=none; b=n6ygpK9ZRQ47RstB0wtYnwZfEX7JGwyZggPQ8/XGv4lF1PZQVvZdZLS2kqlcdaoPx9gMgJ2LpB+y5x8T3fSHmYwrEyg9La04cccOZ0K4CMFapYEN4Ru2Mlo9Vcr9UPLcaeSOn4bSYoOMMNg6vIMJUWC/F3eqlBbdi9qzEo3oS3Q= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1736913219; c=relaxed/simple; bh=0s2TaLPITNZgbrpX6AdtBSLUabw5dyWkhwRq5Z93L7o=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=j/IIgktajU5+ZgQ2zOh7DZSNTi5ae7AM2hgZVhHgAjgb9vY8jQB4AFSTPLxlDs+xitNcplNXg6wwbNqoKzBFumGqQdkX/XhUD+CrptNMHw9gQYRYUBq6EaFu4G/zDXzY/4FKd9stRiFmG95KT5H5nJp/Qrs10kQaFkfRraTM4G0= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=lv/rlPfI; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="lv/rlPfI" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D3AF9C4CEE2; Wed, 15 Jan 2025 03:53:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1736913219; bh=0s2TaLPITNZgbrpX6AdtBSLUabw5dyWkhwRq5Z93L7o=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=lv/rlPfI/N89JdyYF7Cd+upntyCzbNeT5JcCmmPBv5Bl5w03f+RU1BLp4dcjZttsk YYQYSpymziP5YBNk33GVULTuhOKAuC71HKdrBBDZNK0sojbYRGiJe8wACYYZ1Ekyw3 4oR6+djdU1KgfCeBwhR0GmoGmbEQcs9E10y05WMHP5c6+sZgEHJ+q2jBmJeOb4KBux ra+eizzOevrKP945SIXf0crYGuWqKpRqOFPZKGmKhx40SJnKEbnv8j5Nr9fHvB8Rsk oZJII9vsT0k0+1MrgIZdzbokr4H8J5tXEml6Ys6+gWwRRtFZ1FFkpq2nAsqqPXlSJi kTY2q2PUB6b9A== From: Jakub Kicinski To: davem@davemloft.net Cc: netdev@vger.kernel.org, edumazet@google.com, pabeni@redhat.com, andrew+netdev@lunn.ch, horms@kernel.org, jdamato@fastly.com, Jakub Kicinski Subject: [PATCH net-next v2 04/11] net: add netdev->up protected by netdev_lock() Date: Tue, 14 Jan 2025 19:53:12 -0800 Message-ID: <20250115035319.559603-5-kuba@kernel.org> X-Mailer: git-send-email 2.48.0 In-Reply-To: <20250115035319.559603-1-kuba@kernel.org> References: <20250115035319.559603-1-kuba@kernel.org> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Patchwork-Delegate: kuba@kernel.org Some uAPI (netdev netlink) hide net_device's sub-objects while the interface is down to ensure uniform behavior across drivers. To remove the rtnl_lock dependency from those uAPIs we need a way to safely tell if the device is down or up. Add an indication of whether device is open or closed, protected by netdev->lock. The semantics are the same as IFF_UP, but taking netdev_lock around every write to ->flags would be a lot of code churn. We don't want to blanket the entire open / close path by netdev_lock, because it will prevent us from applying it to specific structures - core helpers won't be able to take that lock from any function called by the drivers on open/close paths. So the state of the flag is "pessimistic", as in it may report false negatives, but never false positives. Reviewed-by: Joe Damato Reviewed-by: Eric Dumazet Signed-off-by: Jakub Kicinski Reviewed-by: Kuniyuki Iwashima --- v2: - rework the kdoc to please Sphinx v1: https://lore.kernel.org/20250114035118.110297-5-kuba@kernel.org --- include/linux/netdevice.h | 14 +++++++++++++- net/core/dev.h | 12 ++++++++++++ net/core/dev.c | 4 ++-- 3 files changed, 27 insertions(+), 3 deletions(-) diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h index 30963c5d409b..fdf3a8d93185 100644 --- a/include/linux/netdevice.h +++ b/include/linux/netdevice.h @@ -2443,12 +2443,24 @@ struct net_device { unsigned long gro_flush_timeout; u32 napi_defer_hard_irqs; + /** + * @up: copy of @state's IFF_UP, but safe to read with just @lock. + * May report false negatives while the device is being opened + * or closed (@lock does not protect .ndo_open, or .ndo_close). + */ + bool up; + /** * @lock: netdev-scope lock, protects a small selection of fields. * Should always be taken using netdev_lock() / netdev_unlock() helpers. * Drivers are free to use it for other protection. * - * Protects: @reg_state, @net_shaper_hierarchy. + * Protects: + * @net_shaper_hierarchy, @reg_state + * + * Partially protects (writers must hold both @lock and rtnl_lock): + * @up + * * Ordering: take after rtnl_lock. */ struct mutex lock; diff --git a/net/core/dev.h b/net/core/dev.h index 25ae732c0775..ef37e2dd44f4 100644 --- a/net/core/dev.h +++ b/net/core/dev.h @@ -128,6 +128,18 @@ void __dev_notify_flags(struct net_device *dev, unsigned int old_flags, void unregister_netdevice_many_notify(struct list_head *head, u32 portid, const struct nlmsghdr *nlh); +static inline void netif_set_up(struct net_device *dev, bool value) +{ + if (value) + dev->flags |= IFF_UP; + else + dev->flags &= ~IFF_UP; + + netdev_lock(dev); + dev->up = value; + netdev_unlock(dev); +} + static inline void netif_set_gso_max_size(struct net_device *dev, unsigned int size) { diff --git a/net/core/dev.c b/net/core/dev.c index c871e2697fb6..4cba553a4742 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -1618,7 +1618,7 @@ static int __dev_open(struct net_device *dev, struct netlink_ext_ack *extack) if (ret) clear_bit(__LINK_STATE_START, &dev->state); else { - dev->flags |= IFF_UP; + netif_set_up(dev, true); dev_set_rx_mode(dev); dev_activate(dev); add_device_randomness(dev->dev_addr, dev->addr_len); @@ -1697,7 +1697,7 @@ static void __dev_close_many(struct list_head *head) if (ops->ndo_stop) ops->ndo_stop(dev); - dev->flags &= ~IFF_UP; + netif_set_up(dev, false); netpoll_poll_enable(dev); } }