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=-5.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, 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 B4013C433B4 for ; Mon, 3 May 2021 18:24:43 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id E1EFC61283 for ; Mon, 3 May 2021 18:24:42 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E1EFC61283 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=lst.de Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 6718B6B0070; Mon, 3 May 2021 14:24:42 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 621C06B0071; Mon, 3 May 2021 14:24:42 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 4E99E6B0073; Mon, 3 May 2021 14:24:42 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0025.hostedemail.com [216.40.44.25]) by kanga.kvack.org (Postfix) with ESMTP id 3008A6B0070 for ; Mon, 3 May 2021 14:24:42 -0400 (EDT) Received: from smtpin32.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id E6E336D79 for ; Mon, 3 May 2021 18:24:41 +0000 (UTC) X-FDA: 78100745562.32.452CF6A Received: from verein.lst.de (verein.lst.de [213.95.11.211]) by imf08.hostedemail.com (Postfix) with ESMTP id 1E33F80192F3 for ; Mon, 3 May 2021 18:24:16 +0000 (UTC) Received: by verein.lst.de (Postfix, from userid 2407) id 6C9EA68B05; Mon, 3 May 2021 20:24:35 +0200 (CEST) Date: Mon, 3 May 2021 20:24:35 +0200 From: Christoph Hellwig To: John Hubbard 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, Stephen Bates , Christoph Hellwig , Dan Williams , Jason Gunthorpe , Christian =?iso-8859-1?Q?K=F6nig?= , Don Dutile , Matthew Wilcox , Daniel Vetter , Jakowski Andrzej , Minturn Dave B , Jason Ekstrand , Dave Hansen , Xiong Jianxin , Bjorn Helgaas , Ira Weiny , Robin Murphy , Bjorn Helgaas Subject: Re: [PATCH 01/16] PCI/P2PDMA: Pass gfp_mask flags to upstream_bridge_distance_warn() Message-ID: <20210503182434.GA17174@lst.de> References: <20210408170123.8788-1-logang@deltatee.com> <20210408170123.8788-2-logang@deltatee.com> <8ea5b5b3-e10f-121a-bd2a-07db83c6da01@deltatee.com> <3bced3a4-b826-46ab-3d98-d2dc6871bfe1@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <3bced3a4-b826-46ab-3d98-d2dc6871bfe1@nvidia.com> User-Agent: Mutt/1.5.17 (2007-11-01) Authentication-Results: imf08.hostedemail.com; dkim=none; dmarc=none; spf=none (imf08.hostedemail.com: domain of hch@lst.de has no SPF policy when checking 213.95.11.211) smtp.mailfrom=hch@lst.de X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 1E33F80192F3 X-Stat-Signature: 39cngki6c9tgxr8enswww6qcc6sh5w3y Received-SPF: none (lst.de>: No applicable sender policy available) receiver=imf08; identity=mailfrom; envelope-from=""; helo=verein.lst.de; client-ip=213.95.11.211 X-HE-DKIM-Result: none/none X-HE-Tag: 1620066256-31091 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, May 03, 2021 at 11:17:31AM -0700, John Hubbard wrote: > That's the thing: memory failure should be exceedingly rare for this. > Therefore, just fail out entirely (which I don't expect we'll likely > ever see), instead of doing all this weird stuff to try to continue > on if you cannot allocate a single page. If you are in that case, the > system is not in a state that is going to run your dma p2p setup well > anyway. > > I think it's *less* complexity to allocate up front, fail early if > allocation fails, and then not have to deal with these really odd > quirks at the lower levels. Agreed.