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 16CF4C43215 for ; Thu, 14 Nov 2019 07:19:08 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id D59192068F for ; Thu, 14 Nov 2019 07:19:07 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D59192068F 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 505306B0003; Thu, 14 Nov 2019 02:19:07 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 4B5846B0005; Thu, 14 Nov 2019 02:19:07 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 41A476B0006; Thu, 14 Nov 2019 02:19:07 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0039.hostedemail.com [216.40.44.39]) by kanga.kvack.org (Postfix) with ESMTP id 2DEC16B0003 for ; Thu, 14 Nov 2019 02:19:07 -0500 (EST) Received: from smtpin20.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with SMTP id BC468824999B for ; Thu, 14 Nov 2019 07:19:06 +0000 (UTC) X-FDA: 76154031492.20.rain74_89b420d4d6007 X-HE-Tag: rain74_89b420d4d6007 X-Filterd-Recvd-Size: 2529 Received: from verein.lst.de (verein.lst.de [213.95.11.211]) by imf47.hostedemail.com (Postfix) with ESMTP for ; Thu, 14 Nov 2019 07:19:06 +0000 (UTC) Received: by verein.lst.de (Postfix, from userid 2407) id 2FE8B68AFE; Thu, 14 Nov 2019 08:19:03 +0100 (CET) Date: Thu, 14 Nov 2019 08:19:03 +0100 From: Christoph Hellwig To: Dan Williams Cc: jhubbard@nvidia.com, Jan Kara , Christoph Hellwig , Ira Weiny , =?iso-8859-1?B?Suly9G1l?= Glisse , linux-nvdimm@lists.01.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH] mm: Cleanup __put_devmap_managed_page() vs ->page_free() Message-ID: <20191114071903.GA26307@lst.de> References: <157368992671.2974225.13512647385398246617.stgit@dwillia2-desk3.amr.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <157368992671.2974225.13512647385398246617.stgit@dwillia2-desk3.amr.corp.intel.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 Wed, Nov 13, 2019 at 04:07:22PM -0800, Dan Williams wrote: > static int devmap_managed_enable_get(struct dev_pagemap *pgmap) > { > - if (!pgmap->ops || !pgmap->ops->page_free) { > + if (!pgmap->ops || (pgmap->type == MEMORY_DEVICE_PRIVATE > + && !pgmap->ops->page_free)) { I don't think this check is correct. You only want the the ops null check or MEMORY_DEVICE_PRIVATE as well now, i.e.: if (pgmap->type == MEMORY_DEVICE_PRIVATE && (!pgmap->ops || !pgmap->ops->page_free)) { > @@ -476,10 +471,17 @@ void __put_devmap_managed_page(struct page *page) > * handled differently or not done at all, so there is no need > * to clear page->mapping. > */ > - if (is_device_private_page(page)) > - page->mapping = NULL; > + if (is_device_private_page(page)) { > + /* Clear Active bit in case of parallel mark_page_accessed */ This adds a > 80 char line. But that whole flow of the function seems rather odd now. Why can't we do: if (count == 0) { __put_page(page); } else if (is_device_private_page(page)) { __ClearPageActive(page); __ClearPageWaiters(page); mem_cgroup_uncharge(page); page->mapping = NULL; page->pgmap->ops->page_free(page); } else { wake_up_var(&page->_refcount); } (except for the fact that I don't get the point of calling __put_page on a refcount of zero, but that is separate from this patch).