From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id B7DC0C32793 for ; Wed, 24 Aug 2022 14:07:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238845AbiHXOHB (ORCPT ); Wed, 24 Aug 2022 10:07:01 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48210 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239093AbiHXOGm (ORCPT ); Wed, 24 Aug 2022 10:06:42 -0400 Received: from mail-oi1-x233.google.com (mail-oi1-x233.google.com [IPv6:2607:f8b0:4864:20::233]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 694F098589 for ; Wed, 24 Aug 2022 07:06:40 -0700 (PDT) Received: by mail-oi1-x233.google.com with SMTP id p187so12405134oia.9 for ; Wed, 24 Aug 2022 07:06:40 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=paul-moore-com.20210112.gappssmtp.com; s=20210112; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:from:to:cc; bh=vuqWnah213DNr5H1tn4ngrXQB2l3I0G5wL/BS1TfAHU=; b=4CTpJ2CA2srjZiBgpJuzNh70tqshr8M8JZlh7r1vXXVe6IkKJhWj6f4e/oyuwHt9Cb 3ln3zssJi3/pDymbdZrNuaLokwogS6IeSaFCwh7v2xh9C6Pf6DYvpmhiPTReI6BytPaw iA735qCdspKC9+CznKtPS/nrI1eN9pLMdI3UTMhQ4yXncb0O77D723FMO/Oxi4q0XTXM luM2X2HyV3tuUM5yr2TJQopFdQXCDRMzhFsIPw5GsE405w7wWX59Cc9EJx6j3SxvQL4U ckB3+eYS/hH7UYXu+LIzeBg5ohZDojQNDcmw1b9TFqJRo786YF8i4Scqd1QmijDO/R0y AzJg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:x-gm-message-state:from:to:cc; bh=vuqWnah213DNr5H1tn4ngrXQB2l3I0G5wL/BS1TfAHU=; b=7GecpuaiAyZIK4GKNz6gmPUOQXMCkMoZVHv2Sdrp7g+EWeP81QasgebQOocXyRFInQ SN/Cm74j1xvl3HO2oLyim/ZEw5h/awGxDxh48TV2wr4+L6ez5tkQmVu1vnJE88YgCKLm KZWFiJ1ELvPgRN9zZDyi5tzWx5+1akm5X3T+CJPe3tRRVHbspar+mtNN+46mYHOUhddo tIJbolufVi+bvgCHw9fp4uqhcllewh9u9TyfzJ/n+R77bfmUmP94dwBReWrho4Dl/4Fh a5CShD4ckCuWMPxGSvwzBBUR6EJ8kmoJrWupn3f08qr+u3/NpJHIYM/qe5vH8Yblc/8V 8inQ== X-Gm-Message-State: ACgBeo2b0RKnR2oE2qg4W/MNmklMVKbTROCq9ftEe0GY6Ci0ss76SPAs +13gBeE+1SHlrjfwdrjD+Ha6i0NlwU5Ve7UUvcw/ X-Google-Smtp-Source: AA6agR4kZuDhD9CQWEqCwv8GJP/H3Oi3rbFzJ9S9hgeov6GQmqTZiX0PeLxSUp3Vuw5SBnCLVZ9Lcjz5OyT5kUXOn0Q= X-Received: by 2002:a05:6808:3a9:b0:343:4b14:ccce with SMTP id n9-20020a05680803a900b003434b14cccemr3332125oie.41.1661349999371; Wed, 24 Aug 2022 07:06:39 -0700 (PDT) MIME-Version: 1.0 References: <166120321387.369593.7400426327771894334.stgit@olly> <166120327984.369593.8371751426301540450.stgit@olly> In-Reply-To: From: Paul Moore Date: Wed, 24 Aug 2022 10:06:28 -0400 Message-ID: Subject: Re: [PATCH 3/3] /dev/null: add IORING_OP_URING_CMD support To: Greg Kroah-Hartman Cc: linux-security-module@vger.kernel.org, selinux@vger.kernel.org, io-uring@vger.kernel.org, Arnd Bergmann , Luis Chamberlain Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org On Wed, Aug 24, 2022 at 2:10 AM Greg Kroah-Hartman wrote: > On Tue, Aug 23, 2022 at 01:02:08PM -0400, Paul Moore wrote: > > On Tue, Aug 23, 2022 at 2:52 AM Greg Kroah-Hartman > > wrote: > > > On Mon, Aug 22, 2022 at 05:21:19PM -0400, Paul Moore wrote: > > > > This patch adds support for the io_uring command pass through, aka > > > > IORING_OP_URING_CMD, to the /dev/null driver. As with all of the > > > > /dev/null functionality, the implementation is just a simple sink > > > > where commands go to die, but it should be useful for developers who > > > > need a simple IORING_OP_URING_CMD test device that doesn't require > > > > any special hardware. > > > > > > Also, shouldn't you document this somewhere? > > > > > > At least in the code itself saying "this is here so that /dev/null works > > > as a io_uring sink" or something like that? Otherwise it just looks > > > like it does nothing at all. > > > > What about read_null() and write_null()? I can definitely add a > > comment (there is no /dev/null documentation in the kernel source tree > > that I can see), but there is clearly precedence for /dev/null having > > "do nothing" file_operations functions. > > Yes, they should "do nothing". Right, I don't think anyone was disputing that. You were asking for a comment for the new function that effectively says "this function does nothing", which seems a little silly given the simplicity of the function, the name, and the context of it all. > write_null() does report that it > consumed everything, why doesn't this function have to also do that? Because a file write (file_operations->write) and a IORING_OP_URING_CMD (file_operations->uring_cmd) are fundamentally different operations; uring_cmd_null() returns 0, which is the success return code for this file op (not to mention a significant number of kernel functions that return an int). -- paul-moore.com