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=-9.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham 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 C3B09C17442 for ; Wed, 13 Nov 2019 04:27:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9214022473 for ; Wed, 13 Nov 2019 04:27:16 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=nvidia.com header.i=@nvidia.com header.b="pj6M3Paz" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727199AbfKME1Q (ORCPT ); Tue, 12 Nov 2019 23:27:16 -0500 Received: from hqemgate15.nvidia.com ([216.228.121.64]:13623 "EHLO hqemgate15.nvidia.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726995AbfKME1P (ORCPT ); Tue, 12 Nov 2019 23:27:15 -0500 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?q?Bj=C3=B6rn=20T=C3=B6pel?= , 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?q?J=C3=A9r=C3=B4me=20Glisse?= , 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 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable 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== Sender: bpf-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org 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, J=C3=A9r=C3=B4me Glisse suggested the refactoring described abo= ve. Suggested-by: J=C3=A9r=C3=B4me Glisse Signed-off-by: Ira Weiny Signed-off-by: John Hubbard --- 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 pa= ge *page) #endif =20 #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; } =20 +static inline bool put_devmap_managed_page(struct page *page) +{ + bool is_devmap =3D page_is_devmap_managed(page); + + if (is_devmap) { + int count =3D 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 =3D=3D 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); =20 #ifdef CONFIG_DEV_PAGEMAP_OPS -void __put_devmap_managed_page(struct page *page) +void free_devmap_managed_page(struct page *page) { - int count =3D page_ref_dec_return(page); + /* Clear Active bit in case of parallel mark_page_accessed */ + __ClearPageActive(page); + __ClearPageWaiters(page); + + mem_cgroup_uncharge(page); =20 /* - * 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 =3D=3D 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 =3D NULL; + if (is_device_private_page(page)) + page->mapping =3D NULL; =20 - 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 */ --=20 2.24.0