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 682A5198E63 for ; Mon, 24 Feb 2025 09:02:18 +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=1740387738; cv=none; b=PUxI4BBVii4cc5waXgp3BjjES/G0kmhUs1mXQyH7ol9odTdzBd9r/DPW+Desbb8593wh5nABSvxAvibvY/6+9KMpC0Z2t7/Mj6H5I77hYkV/TLWd8f+WqorzBrHTwPKDCqwixlJrCj1/5DLVInk5kF9rblUpBXU1lublyNwIOIs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1740387738; c=relaxed/simple; bh=TaAnkgvwP/TvvrfdAl8NX9efJWboefZ0h+g5g0c+Eyo=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=nUnBLsJesSx41f9G9hc5iUEA9hNtQuCh2avtaJd/2TSO2CtJVE75a1PqL+T8lPXQ8PyYvHeuGf6dIKormAK3fUIx7hzZDEcXIGHzHTVDPojNOkW2s59nQL2Y9mGrsh+Nq3/NEldGF46PwPsKWze8pqKBIuiwJyuhURLJYve0Yi8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=lFqEF6gC; 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="lFqEF6gC" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E1B33C4CED6; Mon, 24 Feb 2025 09:02:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1740387737; bh=TaAnkgvwP/TvvrfdAl8NX9efJWboefZ0h+g5g0c+Eyo=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=lFqEF6gCFcNFVBtl+46XkMmyfmptLiYHsTIeaCJwKsvEFm7yLsQB/IiHkJQqunS2q 1T/rRQFFKnWy9pkOTVG5xLCwmvDaArgrz9s8hYkr+59Pfl0ffzP2eJtvkHfD53AxZU ilVm3C1oSyHlBrUvWhY5TuPOPfgeQ8oo/VUJC6qF+CLcxXMB489vBZ1/yenfQ4X9Yv i65TFAizg+9vIzNqQVSM/j6Rgy65vyPebqtqa9qnHVBCCNXMGTPPklBRiaWh2Q7Kk5 H/nc2dbC/4GsfI6bPSBaYHALND5dwLr8dfIEh+2Su1jHKM924Ma19dHoqI7IllFiSq 8gyyuFG3/3i/g== Message-ID: Date: Mon, 24 Feb 2025 10:02:15 +0100 Precedence: bulk X-Mailing-List: mptcp@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Beta Subject: Re: [PATCH mptcp-next v3 3/5] Squash to "bpf: Add mptcp_subflow bpf_iter" Content-Language: en-GB To: Geliang Tang , mptcp@lists.linux.dev Cc: Geliang Tang References: <64115dfbaa4e31a997cdaa8c8195eeeae4fab247.camel@kernel.org> From: Matthieu Baerts Autocrypt: addr=matttbe@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 8bit Hi Geliang, On 24/02/2025 09:31, Geliang Tang wrote: > Hi Mat, > > Thanks for the review. > > On Thu, 2025-02-20 at 19:25 +0100, Matthieu Baerts wrote: >> Hi Geliang, >> >> On 17/02/2025 11:34, Geliang Tang wrote: >>> From: Geliang Tang >>> >>> Drop the NULL check for 'msk' as Martin suggested, add more checks >>> for 'sk'. >>> >>> Use the "struct sock *sk" instead of "struct mptcp-sock *msk" as >>> the >>> argument in the bpf_iter_mptcp_subflow_new as Martin suggested. >>> >>> v3: >>>  - continue to use sock_owned_by_user_nocheck and spin_is_locked >>> checks instead of using msk_owned_by_me(). >> >> Why should we continue to do so? >> >> From what I understood, with the current version, this new >> bpf_iter_mptcp_subflow_new kfunc can only be called from a cg sockopt >> bpf prog, which means these checks are not needed for the moment, no? > > Thanks for the clarification. I re-read Martin's comments and he also > suggested removing these checks. So I removed it in v4. Thanks! >> So maybe we should only add these checks later, when extending its >> usage >> to struct_ops? In the meantime, msk_owned_by_me() could then be used >> instead? > > Do I need to add a patch into the "use bpf_iter in bpf schedulers" set > that is under review to do these checks? Do you mean that using > msk_owned_by_me() is enough for struct_ops, and there is no need to use > sock_owned_by_user_nocheck() and spin_is_locked() checks? My understanding is that if a kfunc is set to used in 'struct_ops', it can be used with any 'struct_ops', and not a specific one. Is this correct? - If yes, it means we don't really know in which context a kfunc will be used, thus we need additional checks. But... this feels wrong: if kfunc's cannot be restricted to specific 'struct_ops', probably this should be reported to the BPF maintainers, and see if it could be possible to have such restriction not to add unneeded checks at run time. - If the MPTCP kfunc can be restricted to MPTCP 'struct_ops' where we know the msk lock will be taken, then no need to add these checks if they are useless. Cheers, Matt -- Sponsored by the NGI0 Core fund.