From patchwork Sat Aug 29 08:08:51 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: John Hubbard X-Patchwork-Id: 11744221 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 D7B221751 for ; Sat, 29 Aug 2020 08:09:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C0CB121473 for ; Sat, 29 Aug 2020 08:09:24 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=nvidia.com header.i=@nvidia.com header.b="GeCR42p0" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727941AbgH2IJB (ORCPT ); Sat, 29 Aug 2020 04:09:01 -0400 Received: from hqnvemgate24.nvidia.com ([216.228.121.143]:6667 "EHLO hqnvemgate24.nvidia.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727931AbgH2II4 (ORCPT ); Sat, 29 Aug 2020 04:08:56 -0400 Received: from hqpgpgate101.nvidia.com (Not Verified[216.228.121.13]) by hqnvemgate24.nvidia.com (using TLS: TLSv1.2, DES-CBC3-SHA) id ; Sat, 29 Aug 2020 01:06:51 -0700 Received: from hqmail.nvidia.com ([172.20.161.6]) by hqpgpgate101.nvidia.com (PGP Universal service); Sat, 29 Aug 2020 01:08:55 -0700 X-PGP-Universal: processed; by hqpgpgate101.nvidia.com on Sat, 29 Aug 2020 01:08:55 -0700 Received: from HQMAIL107.nvidia.com (172.20.187.13) by HQMAIL107.nvidia.com (172.20.187.13) with Microsoft SMTP Server (TLS) id 15.0.1473.3; Sat, 29 Aug 2020 08:08:54 +0000 Received: from hqnvemgw03.nvidia.com (10.124.88.68) by HQMAIL107.nvidia.com (172.20.187.13) with Microsoft SMTP Server (TLS) id 15.0.1473.3 via Frontend Transport; Sat, 29 Aug 2020 08:08:54 +0000 Received: from sandstorm.nvidia.com (Not Verified[10.2.50.252]) by hqnvemgw03.nvidia.com with Trustwave SEG (v7,5,8,10121) id ; Sat, 29 Aug 2020 01:08:54 -0700 From: John Hubbard To: Andrew Morton CC: Alexander Viro , Christoph Hellwig , Ilya Dryomov , Jens Axboe , , , , , LKML , John Hubbard Subject: [PATCH v2 1/3] mm/gup: introduce pin_user_page() Date: Sat, 29 Aug 2020 01:08:51 -0700 Message-ID: <20200829080853.20337-2-jhubbard@nvidia.com> X-Mailer: git-send-email 2.28.0 In-Reply-To: <20200829080853.20337-1-jhubbard@nvidia.com> References: <20200829080853.20337-1-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=1598688411; bh=nt0PtF6oHhEk4Ehi11ZCG1lTaPX813pQeWdo2szO18M=; h=X-PGP-Universal:From:To:CC:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:X-NVConfidentiality: Content-Transfer-Encoding:Content-Type; b=GeCR42p0vG1Y/mcPDPfFg8Jr+t+lxTu2SPIfM2gbW6ioXBlHyDFBEpuWKpukI54u+ wsuDo2DHLHKzyLlIOzIMY4I1LBumbthJEXfQmWXbbOStiZGBDqfFygVpB3cAvHtCxJ O7vNWk/2AOqUKjPA6p+gj8ZomZWK4+T5oteaJhEgJEmZcyDIMb4EFnfTlOEIici30Q IBgbsi1Eg0hhZ4Jobh5b6/CjdUvus97FqFJ/WqgEUtSAFqIA33aVOm1GONjDKd6GC3 ODte/dvdN6LsXZp/2yOMJiuHmDsUiIwW+lNAgUdH40w5HufWhROtZDg4IwW21uTptn FfBYqJQiWcdAg== Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org pin_user_page() is the FOLL_PIN equivalent of get_page(). This was always a missing piece of the pin/unpin API calls (early reviewers of pin_user_pages() asked about it, in fact), but until now, it just wasn't needed. Finally though, now that the Direct IO pieces in block/bio are about to be converted to use FOLL_PIN, it turns out that there are some cases in which get_page() and get_user_pages_fast() were both used. Converting those sites requires a drop-in replacement for get_page(), which this patch supplies. [1] and [2] provide some background about pin_user_pages() in general. [1] "Explicit pinning of user-space pages": https://lwn.net/Articles/807108/ [2] Documentation/core-api/pin_user_pages.rst Signed-off-by: John Hubbard --- include/linux/mm.h | 2 ++ mm/gup.c | 30 ++++++++++++++++++++++++++++++ 2 files changed, 32 insertions(+) diff --git a/include/linux/mm.h b/include/linux/mm.h index 97c83773b6f0..51c6ae4b63f7 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -1152,6 +1152,8 @@ static inline void get_page(struct page *page) page_ref_inc(page); } +void pin_user_page(struct page *page); + bool __must_check try_grab_page(struct page *page, unsigned int flags); static inline __must_check bool try_get_page(struct page *page) diff --git a/mm/gup.c b/mm/gup.c index ae096ea7583f..2cae5bbbc862 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -123,6 +123,36 @@ static __maybe_unused struct page *try_grab_compound_head(struct page *page, return NULL; } +/* + * pin_user_page() - elevate the page refcount, and mark as FOLL_PIN + * + * This the FOLL_PIN equivalent of get_page(). It is intended for use when the + * page will be released via unpin_user_page(). + */ +void pin_user_page(struct page *page) +{ + int refs = 1; + + page = compound_head(page); + + VM_BUG_ON_PAGE(page_ref_count(page) <= 0, page); + + if (hpage_pincount_available(page)) + hpage_pincount_add(page, 1); + else + refs = GUP_PIN_COUNTING_BIAS; + + /* + * Similar to try_grab_compound_head(): even if using the + * hpage_pincount_add/_sub() routines, be sure to + * *also* increment the normal page refcount field at least + * once, so that the page really is pinned. + */ + page_ref_add(page, refs); + + mod_node_page_state(page_pgdat(page), NR_FOLL_PIN_ACQUIRED, 1); +} + /** * try_grab_page() - elevate a page's refcount by a flag-dependent amount *