From mboxrd@z Thu Jan 1 00:00:00 1970 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 449601D362B; Tue, 5 Nov 2024 13:40:01 +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=1730814001; cv=none; b=UToxdvH4yKgBvAO5hkG3ZyYvL6XBbR4COBYVeT3vlrxndWt99i8MFfz1upevLEcoZ0GNgJsapimfdiN0YlDZ+MhNn28kLTwCw/sIh4p+iScENWWPmwVgiMAJ69zMIWMaBr69CrS2dJKR4qNz9FLr3AjRty3F3jN9IhHJOJzt4MM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730814001; c=relaxed/simple; bh=X+jkMNJf202J2qCII6QtiwBjooGAeSjJ1FivbkrQ/d0=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=QoSTOKlfPp5Hq5Ei2oPdNuw0wYbYMkcEXlHP16s549abaWAa8ZSKobizJpgnrJtDCUKfjhwO05es0ra+B26oE604CfF/d80PHMXvBnC52Sz9Nvzj1rDw15I1WgbmSikl0YbD1fpAXiXmLRBqQDmPBLXlWdvTFQqmWzItOy36mB4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=DxznB3XN; 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="DxznB3XN" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 290FFC4CECF; Tue, 5 Nov 2024 13:39:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1730814001; bh=X+jkMNJf202J2qCII6QtiwBjooGAeSjJ1FivbkrQ/d0=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=DxznB3XNa4vSg81xiTd126Ga2cYMH4eJmxgA+UrsT35LqYbnBJAcre2w+sNMcA1kz Fui4F3KUj/muw3CweyuZLGcaVLtaB7IIzjfcYXAXFtE+vRvpmdxKboOp6OUj9APMZL oJqiBpus//Kok5GG9yLpJLa9+po7ExY1uF0jBRP0AcY8ddRSR8u69yDhxQKSr2UH/h TeKwFZXRU1KO5XN8DQpvG6Rb9avbf55CxHEKkgDdaiWVHfvE+LY/SExhlSWf+0aIMq qSXR+51W+/JVvCpCpH5sgsfhF66SApK3g+L2TtpILpsMMSS538baIiV5lF6SKvpyA4 i/cQKYjzwCG5w== Date: Tue, 5 Nov 2024 15:39:55 +0200 From: Leon Romanovsky To: Wenjia Zhang Cc: Wen Gu , "D. Wythe" , Tony Lu , David Miller , Jakub Kicinski , Eric Dumazet , Paolo Abeni , netdev@vger.kernel.org, linux-rdma@vger.kernel.org, linux-s390@vger.kernel.org, Heiko Carstens , Jan Karcher , Gerd Bayer , Alexandra Winter , Halil Pasic , Nils Hoppmann , Niklas Schnell , Thorsten Winkler , Karsten Graul , Stefan Raspl , Aswin K Subject: Re: [PATCH net] net/smc: Fix lookup of netdev by using ib_device_get_netdev() Message-ID: <20241105133955.GF311159@unreal> References: <20241025072356.56093-1-wenjia@linux.ibm.com> <20241027201857.GA1615717@unreal> <8d17b403-aefa-4f36-a913-7ace41cf2551@linux.ibm.com> <20241105112313.GE311159@unreal> Precedence: bulk X-Mailing-List: netdev@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: On Tue, Nov 05, 2024 at 01:30:24PM +0100, Wenjia Zhang wrote: > > > On 05.11.24 12:23, Leon Romanovsky wrote: > > On Tue, Nov 05, 2024 at 10:50:45AM +0100, Wenjia Zhang wrote: > > > > > > > > > On 27.10.24 21:18, Leon Romanovsky wrote: > > > > On Fri, Oct 25, 2024 at 09:23:55AM +0200, Wenjia Zhang wrote: > > > > > Commit c2261dd76b54 ("RDMA/device: Add ib_device_set_netdev() as an > > > > > alternative to get_netdev") introduced an API ib_device_get_netdev. > > > > > The SMC-R variant of the SMC protocol continued to use the old API > > > > > ib_device_ops.get_netdev() to lookup netdev. > > > > > > > > I would say that calls to ibdev ops from ULPs was never been right > > > > thing to do. The ib_device_set_netdev() was introduced for the drivers. > > > > > > > > So the whole commit message is not accurate and better to be rewritten. > > > > > > > > > As this commit 8d159eb2117b > > > > > ("RDMA/mlx5: Use IB set_netdev and get_netdev functions") removed the > > > > > get_netdev callback from mlx5_ib_dev_common_roce_ops, calling > > > > > ib_device_ops.get_netdev didn't work any more at least by using a mlx5 > > > > > device driver. > > > > > > > > It is not a correct statement too. All modern drivers (for last 5 years) > > > > don't have that .get_netdev() ops, so it is not mlx5 specific, but another > > > > justification to say that SMC-R was doing it wrong. > > > > > > > > > Thus, using ib_device_set_netdev() now became mandatory. > > > > > > > > ib_device_set_netdev() is mandatory for the drivers, it is nothing to do > > > > with ULPs. > > > > > > > > > > > > > > Replace ib_device_ops.get_netdev() with ib_device_get_netdev(). > > > > > > > > It is too late for me to do proper review for today, but I would say > > > > that it is worth to pay attention to multiple dev_put() calls in the > > > > functions around the ib_device_get_netdev(). > > > > > > > > > > > > > > Fixes: 54903572c23c ("net/smc: allow pnetid-less configuration") > > > > > Fixes: 8d159eb2117b ("RDMA/mlx5: Use IB set_netdev and get_netdev functions") > > > > > > > > It is not related to this change Fixes line. > > > > > > > > > > Hi Leon, > > > > > > Thank you for the review! I agree that SMC could do better. However, we > > > should fix it and give enough information and reference on the changes, > > > since the code has already existed and didn't work with the old way. > > > > The code which you change worked by chance and was wrong from day one. > > > > > I can rewrite the commit message. > > > > > > What about: > > > " > > > The SMC-R variant of the SMC protocol still called > > > ib_device_ops.get_netdev() to lookup netdev. As we used mlx5 device driver > > > to run SMC-R, it failed to find a device, because in mlx5_ib the internal > > > net device management for retrieving net devices was replaced by a common > > > interface ib_device_get_netdev() in commit 8d159eb2117b ("RDMA/mlx5: Use IB > > > set_netdev and get_netdev functions"). Thus, replace > > > ib_device_ops.get_netdev() with ib_device_get_netdev() in SMC. > > > " > > > > The SMC-R variant of the SMC protocol used direct call to ib_device_ops.get_netdev() > > function to lookup netdev. Such direct accesses are not correct for any > > usage outside of RDMA core code. > > > Is such an absolute statement documented somewhere? If not, I don't think > it's convenient that I use it. Maybe you guys as RDMA core maintainer can, > not I. You can too as it is very clear. All functions which can be used have EXPORT_SYMBOL near them, ops.get_netdev() has nothing like that. > > RDMA subsystem provides ib_device_get_netdev() function that works on > > all RDMA drivers returns valid netdev with proper locking an reference > > counting. The commit 8d159eb2117b ("RDMA/mlx5: Use IB set_netdev and get_netdev > > functions") exposed that SMC-R didn't use that function. > > > > So update the SMC-R to use proper API, > > > > Thanks > > > mhhh, I'd like to stick to my version, which sounds more neutral IMO. I > think the purpose is the same. I don't want to argue about the words, my point is that get_netdev() was never been the right interface. Thanks > > Thanks, > Wenjia