From patchwork Wed Nov 13 04:26:51 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: John Hubbard X-Patchwork-Id: 11240797 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id C86CF1850 for ; Wed, 13 Nov 2019 04:27:52 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 880C522466 for ; Wed, 13 Nov 2019 04:27:52 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=nvidia.com header.i=@nvidia.com header.b="pj6M3Paz" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 880C522466 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=nvidia.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 508CC6B0270; Tue, 12 Nov 2019 23:27:22 -0500 (EST) Delivered-To: linux-mm-outgoing@kvack.org Received: by kanga.kvack.org (Postfix, from userid 40) id 2B7826B026F; Tue, 12 Nov 2019 23:27:22 -0500 (EST) X-Original-To: int-list-linux-mm@kvack.org X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 098746B0272; Tue, 12 Nov 2019 23:27:21 -0500 (EST) X-Original-To: linux-mm@kvack.org X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0246.hostedemail.com [216.40.44.246]) by kanga.kvack.org (Postfix) with ESMTP id C9F686B026D for ; Tue, 12 Nov 2019 23:27:21 -0500 (EST) Received: from smtpin07.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with SMTP id 89CB4181AEF1A for ; Wed, 13 Nov 2019 04:27:21 +0000 (UTC) X-FDA: 76149969882.07.berry88_230c3eaf06a28 X-Spam-Summary: 1,0,0,,d41d8cd98f00b204,jhubbard@nvidia.com,:akpm@linux-foundation.org:viro@zeniv.linux.org.uk:alex.williamson@redhat.com:benh@kernel.crashing.org:bjorn.topel@intel.com:hch@infradead.org:dan.j.williams@intel.com:daniel@ffwll.ch:david@fromorbit.com:airlied@linux.ie:davem@davemloft.net:ira.weiny@intel.com:jack@suse.cz:jgg@ziepe.ca:axboe@kernel.dk:corbet@lwn.net:jglisse@redhat.com:magnus.karlsson@intel.com:mchehab@kernel.org:mpe@ellerman.id.au:mhocko@suse.com:mike.kravetz@oracle.com:paulus@samba.org:shuah@kernel.org:vbabka@suse.cz:bpf@vger.kernel.org:dri-devel@lists.freedesktop.org:kvm@vger.kernel.org:linux-block@vger.kernel.org:linux-doc@vger.kernel.org:linux-fsdevel@vger.kernel.org:linux-kselftest@vger.kernel.org:linux-media@vger.kernel.org:linux-rdma@vger.kernel.org:linuxppc-dev@lists.ozlabs.org:netdev@vger.kernel.org::linux-kernel@vger.kernel.org:jhubbard@nvidia.com,RULES_HIT:30054:30064:30070:30090,0,RBL:216.228.121.64:@nvidia.com:.lbl8.mailshell.net-62.18.0 .100 64. X-HE-Tag: berry88_230c3eaf06a28 X-Filterd-Recvd-Size: 9837 Received: from hqemgate15.nvidia.com (hqemgate15.nvidia.com [216.228.121.64]) by imf21.hostedemail.com (Postfix) with ESMTP for ; Wed, 13 Nov 2019 04:27:20 +0000 (UTC) Received: from hqpgpgate102.nvidia.com (Not Verified[216.228.121.13]) by hqemgate15.nvidia.com (using TLS: TLSv1.2, DES-CBC3-SHA) id ; Tue, 12 Nov 2019 20:27:12 -0800 Received: from hqmail.nvidia.com ([172.20.161.6]) by hqpgpgate102.nvidia.com (PGP Universal service); Tue, 12 Nov 2019 20:27:12 -0800 X-PGP-Universal: processed; by hqpgpgate102.nvidia.com on Tue, 12 Nov 2019 20:27:12 -0800 Received: from HQMAIL101.nvidia.com (172.20.187.10) by HQMAIL105.nvidia.com (172.20.187.12) with Microsoft SMTP Server (TLS) id 15.0.1473.3; Wed, 13 Nov 2019 04:27:12 +0000 Received: from hqnvemgw03.nvidia.com (10.124.88.68) by HQMAIL101.nvidia.com (172.20.187.10) with Microsoft SMTP Server (TLS) id 15.0.1473.3 via Frontend Transport; Wed, 13 Nov 2019 04:27:12 +0000 Received: from blueforge.nvidia.com (Not Verified[10.110.48.28]) by hqnvemgw03.nvidia.com with Trustwave SEG (v7,5,8,10121) id ; Tue, 12 Nov 2019 20:27:12 -0800 From: John Hubbard To: Andrew Morton CC: Al Viro , Alex Williamson , Benjamin Herrenschmidt , =?utf-8?b?QmrDtnJuIFQ=?= =?utf-8?b?w7ZwZWw=?= , Christoph Hellwig , Dan Williams , Daniel Vetter , Dave Chinner , David Airlie , "David S . Miller" , Ira Weiny , Jan Kara , Jason Gunthorpe , Jens Axboe , Jonathan Corbet , =?utf-8?b?SsOpcsO0bWUgR2xpc3Nl?= , Magnus Karlsson , Mauro Carvalho Chehab , Michael Ellerman , Michal Hocko , Mike Kravetz , Paul Mackerras , Shuah Khan , Vlastimil Babka , , , , , , , , , , , , , LKML , John Hubbard Subject: [PATCH v4 04/23] mm: devmap: refactor 1-based refcounting for ZONE_DEVICE pages Date: Tue, 12 Nov 2019 20:26:51 -0800 Message-ID: <20191113042710.3997854-5-jhubbard@nvidia.com> X-Mailer: git-send-email 2.24.0 In-Reply-To: <20191113042710.3997854-1-jhubbard@nvidia.com> References: <20191113042710.3997854-1-jhubbard@nvidia.com> MIME-Version: 1.0 X-NVConfidentiality: public DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nvidia.com; s=n1; t=1573619232; bh=eh5PKTqFnv3H2C1oWk46Hm4jlzYBaiSiPR2xbAo8/Xk=; h=X-PGP-Universal:From:To:CC:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:X-NVConfidentiality: Content-Type:Content-Transfer-Encoding; b=pj6M3Paz4Jb8s/zkr4xbcn7V9rw85SFVXQf2t/30nSh5HeFhZtiu6L2TDkY9LXdBk qmFAmsMXW8K9aqONmx5rzpgcKrp7KyoDoxEcKWWeF72f2hFzO1rgnvWA62qGpVpJpw Fji+h0aQkFAXAMnKj3pPlPYU48JG4GZyXfD/6m7PagtSohgBgvIQp6tKddm+C3WJk9 XcFpVY0yWtBnkeMgSj0/b7hydd7pek7qPo7vhnlFkZz0SUdf+MdspBaUtaMwS2wKLd hFWYy6ySeXIEnL5hOSCfBW1tz3UyYdy4KyiOziT+U/tvErynTern5gpDgfTipG7fZf A69nwyNvr8ktQ== 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: An upcoming patch changes and complicates the refcounting and especially the "put page" aspects of it. In order to keep everything clean, refactor the devmap page release routines: * Rename put_devmap_managed_page() to page_is_devmap_managed(), and limit the functionality to "read only": return a bool, with no side effects. * Add a new routine, put_devmap_managed_page(), to handle checking what kind of page it is, and what kind of refcount handling it requires. * Rename __put_devmap_managed_page() to free_devmap_managed_page(), and limit the functionality to unconditionally freeing a devmap page. This is originally based on a separate patch by Ira Weiny, which applied to an early version of the put_user_page() experiments. Since then, Jérôme Glisse suggested the refactoring described above. Suggested-by: Jérôme Glisse Signed-off-by: Ira Weiny Signed-off-by: John Hubbard Reviewed-by: Jan Kara Reviewed-by: Jérôme Glisse --- include/linux/mm.h | 27 ++++++++++++++++--- mm/memremap.c | 67 ++++++++++++++++++++-------------------------- 2 files changed, 53 insertions(+), 41 deletions(-) diff --git a/include/linux/mm.h b/include/linux/mm.h index a2adf95b3f9c..96228376139c 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -967,9 +967,10 @@ static inline bool is_zone_device_page(const struct page *page) #endif #ifdef CONFIG_DEV_PAGEMAP_OPS -void __put_devmap_managed_page(struct page *page); +void free_devmap_managed_page(struct page *page); DECLARE_STATIC_KEY_FALSE(devmap_managed_key); -static inline bool put_devmap_managed_page(struct page *page) + +static inline bool page_is_devmap_managed(struct page *page) { if (!static_branch_unlikely(&devmap_managed_key)) return false; @@ -978,7 +979,6 @@ static inline bool put_devmap_managed_page(struct page *page) switch (page->pgmap->type) { case MEMORY_DEVICE_PRIVATE: case MEMORY_DEVICE_FS_DAX: - __put_devmap_managed_page(page); return true; default: break; @@ -986,6 +986,27 @@ static inline bool put_devmap_managed_page(struct page *page) return false; } +static inline bool put_devmap_managed_page(struct page *page) +{ + bool is_devmap = page_is_devmap_managed(page); + + if (is_devmap) { + int count = page_ref_dec_return(page); + + /* + * devmap page refcounts are 1-based, rather than 0-based: if + * refcount is 1, then the page is free and the refcount is + * stable because nobody holds a reference on the page. + */ + if (count == 1) + free_devmap_managed_page(page); + else if (!count) + __put_page(page); + } + + return is_devmap; +} + #else /* CONFIG_DEV_PAGEMAP_OPS */ static inline bool put_devmap_managed_page(struct page *page) { diff --git a/mm/memremap.c b/mm/memremap.c index 03ccbdfeb697..bc7e2a27d025 100644 --- a/mm/memremap.c +++ b/mm/memremap.c @@ -410,48 +410,39 @@ struct dev_pagemap *get_dev_pagemap(unsigned long pfn, EXPORT_SYMBOL_GPL(get_dev_pagemap); #ifdef CONFIG_DEV_PAGEMAP_OPS -void __put_devmap_managed_page(struct page *page) +void free_devmap_managed_page(struct page *page) { - int count = page_ref_dec_return(page); + /* Clear Active bit in case of parallel mark_page_accessed */ + __ClearPageActive(page); + __ClearPageWaiters(page); + + mem_cgroup_uncharge(page); /* - * If refcount is 1 then page is freed and refcount is stable as nobody - * holds a reference on the page. + * When a device_private page is freed, the page->mapping field + * may still contain a (stale) mapping value. For example, the + * lower bits of page->mapping may still identify the page as + * an anonymous page. Ultimately, this entire field is just + * stale and wrong, and it will cause errors if not cleared. + * One example is: + * + * migrate_vma_pages() + * migrate_vma_insert_page() + * page_add_new_anon_rmap() + * __page_set_anon_rmap() + * ...checks page->mapping, via PageAnon(page) call, + * and incorrectly concludes that the page is an + * anonymous page. Therefore, it incorrectly, + * silently fails to set up the new anon rmap. + * + * For other types of ZONE_DEVICE pages, migration is either + * handled differently or not done at all, so there is no need + * to clear page->mapping. */ - if (count == 1) { - /* Clear Active bit in case of parallel mark_page_accessed */ - __ClearPageActive(page); - __ClearPageWaiters(page); - - mem_cgroup_uncharge(page); - - /* - * When a device_private page is freed, the page->mapping field - * may still contain a (stale) mapping value. For example, the - * lower bits of page->mapping may still identify the page as - * an anonymous page. Ultimately, this entire field is just - * stale and wrong, and it will cause errors if not cleared. - * One example is: - * - * migrate_vma_pages() - * migrate_vma_insert_page() - * page_add_new_anon_rmap() - * __page_set_anon_rmap() - * ...checks page->mapping, via PageAnon(page) call, - * and incorrectly concludes that the page is an - * anonymous page. Therefore, it incorrectly, - * silently fails to set up the new anon rmap. - * - * For other types of ZONE_DEVICE pages, migration is either - * 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)) + page->mapping = NULL; - page->pgmap->ops->page_free(page); - } else if (!count) - __put_page(page); + page->pgmap->ops->page_free(page); } -EXPORT_SYMBOL(__put_devmap_managed_page); +EXPORT_SYMBOL(free_devmap_managed_page); #endif /* CONFIG_DEV_PAGEMAP_OPS */