From patchwork Thu Dec 19 00:40:37 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: John Hubbard X-Patchwork-Id: 11302507 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 B815714B7 for ; Thu, 19 Dec 2019 00:41:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8C5AF24650 for ; Thu, 19 Dec 2019 00:41:35 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=nvidia.com header.i=@nvidia.com header.b="qjIOKqdC" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726717AbfLSAl0 (ORCPT ); Wed, 18 Dec 2019 19:41:26 -0500 Received: from hqnvemgate24.nvidia.com ([216.228.121.143]:12803 "EHLO hqnvemgate24.nvidia.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726463AbfLSAl0 (ORCPT ); Wed, 18 Dec 2019 19:41:26 -0500 Received: from hqpgpgate101.nvidia.com (Not Verified[216.228.121.13]) by hqnvemgate24.nvidia.com (using TLS: TLSv1.2, DES-CBC3-SHA) id ; Wed, 18 Dec 2019 16:40:11 -0800 Received: from hqmail.nvidia.com ([172.20.161.6]) by hqpgpgate101.nvidia.com (PGP Universal service); Wed, 18 Dec 2019 16:40:40 -0800 X-PGP-Universal: processed; by hqpgpgate101.nvidia.com on Wed, 18 Dec 2019 16:40:40 -0800 Received: from HQMAIL101.nvidia.com (172.20.187.10) by HQMAIL101.nvidia.com (172.20.187.10) with Microsoft SMTP Server (TLS) id 15.0.1473.3; Thu, 19 Dec 2019 00:40:40 +0000 Received: from rnnvemgw01.nvidia.com (10.128.109.123) by HQMAIL101.nvidia.com (172.20.187.10) with Microsoft SMTP Server (TLS) id 15.0.1473.3 via Frontend Transport; Thu, 19 Dec 2019 00:40:39 +0000 Received: from blueforge.nvidia.com (Not Verified[10.110.48.28]) by rnnvemgw01.nvidia.com with Trustwave SEG (v7,5,8,10121) id ; Wed, 18 Dec 2019 16:40:39 -0800 From: John Hubbard To: Andrew Morton CC: "Kirill A . Shutemov" , 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 , Christoph Hellwig Subject: [PATCH v12] mm: devmap: refactor 1-based refcounting for ZONE_DEVICE pages Date: Wed, 18 Dec 2019 16:40:37 -0800 Message-ID: <20191219004037.1198078-1-jhubbard@nvidia.com> X-Mailer: git-send-email 2.24.1 In-Reply-To: <20191218160420.gyt4c45e6zsnxqv6@box> References: <20191218160420.gyt4c45e6zsnxqv6@box> MIME-Version: 1.0 X-NVConfidentiality: public DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nvidia.com; s=n1; t=1576716012; bh=meY7XSFZGFTm0ReBYolvDdqRBgCh/HSlArb5Zg3NFvk=; 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=qjIOKqdCUd7FwtXps/EX5rcy2jzX7ECH7d3gscZlvPWK+USZzY1q0dAG+H1A1e4bW xIdpfAI5t4vavi9qpNMvGtiweIkR1awxL4TYXPZwaeONkFcFN1zXQbpW/68snevPNj 5QIP3HFe/KnwTQJ5t/CB3h4eLlluOox9FBIYdqA3HpeElohSY3KZjP+6dBkbINRhFa ZYRgTzuq1d6+3U/JsKziS6j7uhAZMlje1/Nk/EI1s0RtNW9Xt5H7STM2pMGvX9z96O 6weRpZ4IdcHq5gWYu+R05VYD+Ro8D3XakiiYQK6azXLHolwxZWIhC6GYnIMG6nSLyM S6aDYq/kU5kxg== Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@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 decrementing the refcount for ZONE_DEVICE pages. * Change callers (just release_pages() and put_page()) to check page_is_devmap_managed() before calling the new put_devmap_managed_page() routine. This is a performance point: put_page() is a hot path, so we need to avoid non- inline function calls where possible. * 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. Cc: Christoph Hellwig Suggested-by: Jérôme Glisse Reviewed-by: Dan Williams Reviewed-by: Jan Kara Signed-off-by: Ira Weiny Signed-off-by: John Hubbard --- include/linux/mm.h | 18 +++++++++++++----- mm/memremap.c | 16 ++-------------- mm/swap.c | 27 ++++++++++++++++++++++++++- 3 files changed, 41 insertions(+), 20 deletions(-) diff --git a/include/linux/mm.h b/include/linux/mm.h index c97ea3b694e6..87b54126e46d 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -952,9 +952,10 @@ 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; @@ -963,7 +964,6 @@ 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; @@ -971,11 +971,17 @@ static inline bool put_devmap_managed_page(struct page *page) return false; } +void put_devmap_managed_page(struct page *page); + #else /* CONFIG_DEV_PAGEMAP_OPS */ -static inline bool put_devmap_managed_page(struct page *page) +static inline bool page_is_devmap_managed(struct page *page) { return false; } + +static inline void put_devmap_managed_page(struct page *page) +{ +} #endif /* CONFIG_DEV_PAGEMAP_OPS */ static inline bool is_device_private_page(const struct page *page) @@ -1028,8 +1034,10 @@ static inline void put_page(struct page *page) * need to inform the device driver through callback. See * include/linux/memremap.h and HMM for details. */ - if (put_devmap_managed_page(page)) + if (page_is_devmap_managed(page)) { + put_devmap_managed_page(page); return; + } if (put_page_testzero(page)) __put_page(page); diff --git a/mm/memremap.c b/mm/memremap.c index e899fa876a62..2ba773859031 100644 --- a/mm/memremap.c +++ b/mm/memremap.c @@ -411,20 +411,8 @@ 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); - - /* still busy */ - if (count > 1) - return; - - /* only triggered by the dev_pagemap shutdown path */ - if (count == 0) { - __put_page(page); - return; - } - /* notify page idle for dax */ if (!is_device_private_page(page)) { wake_up_var(&page->_refcount); @@ -461,5 +449,5 @@ void __put_devmap_managed_page(struct page *page) page->mapping = NULL; page->pgmap->ops->page_free(page); } -EXPORT_SYMBOL(__put_devmap_managed_page); +EXPORT_SYMBOL(free_devmap_managed_page); #endif /* CONFIG_DEV_PAGEMAP_OPS */ diff --git a/mm/swap.c b/mm/swap.c index 5341ae93861f..cf39d24ada2a 100644 --- a/mm/swap.c +++ b/mm/swap.c @@ -813,8 +813,10 @@ void release_pages(struct page **pages, int nr) * processing, and instead, expect a call to * put_page_testzero(). */ - if (put_devmap_managed_page(page)) + if (page_is_devmap_managed(page)) { + put_devmap_managed_page(page); continue; + } } page = compound_head(page); @@ -1102,3 +1104,26 @@ void __init swap_setup(void) * _really_ don't want to cluster much more */ } + +#ifdef CONFIG_DEV_PAGEMAP_OPS +void put_devmap_managed_page(struct page *page) +{ + int count; + + if (WARN_ON_ONCE(!page_is_devmap_managed(page))) + return; + + 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); +} +EXPORT_SYMBOL(put_devmap_managed_page); +#endif