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=-5.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 D4D37C433DB for ; Tue, 16 Mar 2021 07:57:29 +0000 (UTC) Received: from desiato.infradead.org (desiato.infradead.org [90.155.92.199]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 71C2864F4D for ; Tue, 16 Mar 2021 07:57:29 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 71C2864F4D Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=lst.de Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=desiato.20200630; h=Sender:Content-Transfer-Encoding :Content-Type:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References:Message-ID: Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=AZuH3nz6Br5n4HWGCERzCZE9Yr8qzMKQQPbPqG4P6Uc=; b=JYMelVHtHpuBBWqqeQp6T+6Ez 2lFB0kODkZkwx27bppSpG/yJMYKx2aYFpypiXV0frbcBcXPNBMfP3dzzh+a/WXzxc3EtqR45WHZWB 996l9w2l7DD7jVEQyULAzrVoS2U8KpgPI8AjGnIjqktZlANYNyE/3jaxjo9CsreIBcZXBRJfbNXxo AHDPWmHaT9gOLJoSUZsMoGjBaHgUwpYjwIrF33UtiBm9lLEvPHT7vmAyo7gbq7r2T43hLFmk0FOe1 lUuehfzbsxn/ZeEguRr6v2mbZHuZMkLJXAXrog0gQVpLiqVcrq0HLauh3nIoK6oGbJEad1TOzdkvV 2tgBkGK0w==; Received: from localhost ([::1] helo=desiato.infradead.org) by desiato.infradead.org with esmtp (Exim 4.94 #2 (Red Hat Linux)) id 1lM4Zg-0002kn-P8; Tue, 16 Mar 2021 07:57:08 +0000 Received: from verein.lst.de ([213.95.11.211]) by desiato.infradead.org with esmtps (Exim 4.94 #2 (Red Hat Linux)) id 1lM4Zb-0002k2-Gj for linux-nvme@lists.infradead.org; Tue, 16 Mar 2021 07:57:05 +0000 Received: by verein.lst.de (Postfix, from userid 2407) id 7222268C4E; Tue, 16 Mar 2021 08:56:58 +0100 (CET) Date: Tue, 16 Mar 2021 08:56:58 +0100 From: Christoph Hellwig To: Robin Murphy Cc: Logan Gunthorpe , 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, Minturn Dave B , John Hubbard , Dave Hansen , Matthew Wilcox , Christian =?iso-8859-1?Q?K=F6nig?= , Jason Gunthorpe , Jason Ekstrand , Daniel Vetter , Dan Williams , Stephen Bates , Jakowski Andrzej , Christoph Hellwig , Xiong Jianxin Subject: Re: [RFC PATCH v2 06/11] dma-direct: Support PCI P2PDMA pages in dma-direct map_sg Message-ID: <20210316075658.GA15949@lst.de> References: <20210311233142.7900-1-logang@deltatee.com> <20210311233142.7900-7-logang@deltatee.com> <215e1472-5294-d20a-a43a-ff6dfe8cd66e@arm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.17 (2007-11-01) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210316_075703_667399_37C147BB X-CRM114-Status: GOOD ( 12.68 ) X-BeenThere: linux-nvme@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "Linux-nvme" Errors-To: linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org On Fri, Mar 12, 2021 at 06:11:17PM +0000, Robin Murphy wrote: > Sure, that's how things stand immediately after this patch. But then > someone comes along with the perfectly reasonable argument for returning > more expressive error information for regular mapping failures as well > (because sometimes those can be terminal too, as above), we start to get > divergent behaviour across architectures and random bits of old code subtly > breaking down the line. *That* is what makes me wary of making a > fundamental change to a long-standing "nonzero means success" interface... Agreed. IMHO dma_map_sg actually needs to be switched to return unsigned to help root this out, going the other way is no helpful. _______________________________________________ Linux-nvme mailing list Linux-nvme@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-nvme