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 X-Spam-Level: X-Spam-Status: No, score=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2F1ECC433E0 for ; Wed, 24 Mar 2021 17:22:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EDB03619FC for ; Wed, 24 Mar 2021 17:22:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237166AbhCXRWG (ORCPT ); Wed, 24 Mar 2021 13:22:06 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59434 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237131AbhCXRWB (ORCPT ); Wed, 24 Mar 2021 13:22:01 -0400 Received: from mail-qt1-x82a.google.com (mail-qt1-x82a.google.com [IPv6:2607:f8b0:4864:20::82a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 87FB1C0613DF for ; Wed, 24 Mar 2021 10:22:00 -0700 (PDT) Received: by mail-qt1-x82a.google.com with SMTP id m7so18115084qtq.11 for ; Wed, 24 Mar 2021 10:22:00 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ziepe.ca; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=SrdP9ZidSNfCaSucoColh3TxPDb0AtWOwMrzkk0oHMo=; b=VqmHlOv5pk7Z6wF8FHX+TfDJjfjh921rYi4eN41NcDt/fq0DBDJOU7rhGSKU6ufyTm xgryyJiAucS8WZzz2ViVbQUPuCpXfg7uEEhpPzzprqcXGMGkBwD6G1BUvjJVBTwjUNRd pCXxJXPAOu8fNVQE1dmK+28ONbnNOcRwtDtStbIduQNJhqkB9Esrou8G0LfcvJrhW4fe ULycH1dWEtxvx55GhkyZoQPGnapSxw7VUycFCKDpkG8+3sa5snIG53zjQV6wfo7BiGMJ HJ9PrsuAPOJka52Tqjh77gZ/r2aV/d7R2K1zypTuv24H1EMPdKj6/CNzp7+bL0NdEvhW NVQw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=SrdP9ZidSNfCaSucoColh3TxPDb0AtWOwMrzkk0oHMo=; b=WTi/hRzpwGDEgXVO15SIhW42Mrp34icP58mChHaX7N6GyptXBmDrFixVz+b19gvc6H jQghgTLWyGd1d0ql/VOetKfofqtnwgvsDFj43hPPQj0xSZ+B32oVcoUFTmj+Jx2gxMgX FgRHj+LIfiahCDCsm6OYoUq4I+bsAqcwg6oOJLRP3uGIv+h4Ly8jDXG3CzgL40LWThmD ZeQV8M8d4xQOAtgmXOcIbUzKfpZakQ/1WHVN1BId5JGFaq7nPjL8dJgdesVqzuMc7hNu 7VBmD5yYg8QTywFTbsNKAxhKal/3WmQGYqzaicwsmP/wxmqU7wLzUqrwddzGzaPPORr/ rcGw== X-Gm-Message-State: AOAM531lyOM/vafoAlOC9fWOJZBnHUCbiLjPeR0oX+H9E+IfO+2CDQow duqukTJ2VV7C+4Zv/NihV9CCuQ== X-Google-Smtp-Source: ABdhPJyneQA4gaMEWYTu19JnLqKtUSbn29vkpMblQHBkTJsjZw2ELWdLSZfb1xoPTIiUK6qAC7wT3Q== X-Received: by 2002:ac8:4d02:: with SMTP id w2mr3864955qtv.126.1616606519694; Wed, 24 Mar 2021 10:21:59 -0700 (PDT) Received: from ziepe.ca ([206.223.160.26]) by smtp.gmail.com with ESMTPSA id q125sm2144133qkf.68.2021.03.24.10.21.59 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 24 Mar 2021 10:21:59 -0700 (PDT) Received: from jgg by mlx with local (Exim 4.94) (envelope-from ) id 1lP7Cf-0025Yq-Vy; Wed, 24 Mar 2021 14:21:58 -0300 Date: Wed, 24 Mar 2021 14:21:57 -0300 From: Jason Gunthorpe To: Logan Gunthorpe Cc: Ira Weiny , linux-kernel@vger.kernel.org, linux-nvme@lists.infradead.org, linux-block@vger.kernel.org, linux-pci@vger.kernel.org, linux-mm@kvack.org, iommu@lists.linux-foundation.org, Stephen Bates , Christoph Hellwig , Dan Williams , Christian =?utf-8?B?S8O2bmln?= , Ira Weiny , John Hubbard , Don Dutile , Matthew Wilcox , Daniel Vetter , Jakowski Andrzej , Minturn Dave B , Jason Ekstrand , Dave Hansen , Xiong Jianxin Subject: Re: [RFC PATCH v2 04/11] PCI/P2PDMA: Introduce pci_p2pdma_should_map_bus() and pci_p2pdma_bus_offset() Message-ID: <20210324172157.GH2710221@ziepe.ca> References: <20210311233142.7900-1-logang@deltatee.com> <20210311233142.7900-5-logang@deltatee.com> <20210313013856.GA3402637@iweiny-DESK2.sc.intel.com> <7509243d-b605-953b-6941-72876a60d527@deltatee.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <7509243d-b605-953b-6941-72876a60d527@deltatee.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Mar 15, 2021 at 10:27:08AM -0600, Logan Gunthorpe wrote: > In this case the WARN_ON is just to guard against misuse of the > function. It should never happen unless a developer changes the code in > a way that is incorrect. So I think that's the correct use of WARN_ON. > Though I might change it to WARN and return, that seems safer. Right, WARN_ON and return is the right pattern for an assertion that must never happen: if (WARN_ON(foo)) return -1 Linus wants assertions like this to be able to recover. People runing the 'panic on warn' mode want the kernel to stop if it detects an internal malfunction. Jason