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=-2.2 required=3.0 tests=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 4B229C47255 for ; Fri, 8 May 2020 19:51:35 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id F1EBF218AC for ; Fri, 8 May 2020 19:51:34 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org F1EBF218AC 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 7D776900003; Fri, 8 May 2020 15:51:34 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 7ACE98E0003; Fri, 8 May 2020 15:51:34 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 7108E900003; Fri, 8 May 2020 15:51:34 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0168.hostedemail.com [216.40.44.168]) by kanga.kvack.org (Postfix) with ESMTP id 5B8E88E0003 for ; Fri, 8 May 2020 15:51:34 -0400 (EDT) Received: from smtpin14.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 1CC378248068 for ; Fri, 8 May 2020 19:51:34 +0000 (UTC) X-FDA: 76794596508.14.pipe88_47d55ac54251d X-HE-Tag: pipe88_47d55ac54251d X-Filterd-Recvd-Size: 2251 Received: from verein.lst.de (verein.lst.de [213.95.11.211]) by imf07.hostedemail.com (Postfix) with ESMTP for ; Fri, 8 May 2020 19:51:33 +0000 (UTC) Received: by verein.lst.de (Postfix, from userid 2407) id 6EAA068C7B; Fri, 8 May 2020 21:51:30 +0200 (CEST) Date: Fri, 8 May 2020 21:51:30 +0200 From: Christoph Hellwig To: Ralph Campbell Cc: nouveau@lists.freedesktop.org, linux-rdma@vger.kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, Jerome Glisse , John Hubbard , Christoph Hellwig , Jason Gunthorpe , Ben Skeggs , Andrew Morton , Shuah Khan , willy@infradead.org Subject: Re: [PATCH 4/6] mm/hmm: add output flag for compound page mapping Message-ID: <20200508195129.GA19740@lst.de> References: <20200508192009.15302-1-rcampbell@nvidia.com> <20200508192009.15302-5-rcampbell@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200508192009.15302-5-rcampbell@nvidia.com> User-Agent: Mutt/1.5.17 (2007-11-01) 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 Fri, May 08, 2020 at 12:20:07PM -0700, Ralph Campbell wrote: > hmm_range_fault() returns an array of page frame numbers and flags for > how the pages are mapped in the requested process' page tables. The PFN > can be used to get the struct page with hmm_pfn_to_page() and the page size > order can be determined with compound_order(page) but if the page is larger > than order 0 (PAGE_SIZE), there is no indication that the page is mapped > using a larger page size. To be fully general, hmm_range_fault() would need > to return the mapping size to handle cases like a 1GB compound page being > mapped with 2MB PMD entries. However, the most common case is the mapping > size the same as the underlying compound page size. > Add a new output flag to indicate this so that callers know it is safe to > use a large device page table mapping if one is available. Why do you need the flag? The caller should be able to just use page_size() (or willys new thp_size helper).