Received: by 2002:a05:6a10:a0d1:0:0:0:0 with SMTP id j17csp742194pxa; Fri, 21 Aug 2020 21:22:51 -0700 (PDT) X-Google-Smtp-Source: ABdhPJxdL3WEAzTh6fyCt1Fn31pRy91keRoNg9lYaX7gL0oCltgYODFGRGTMUuU/bfCoeD/7EPwV X-Received: by 2002:a50:ed88:: with SMTP id h8mr770061edr.360.1598070171490; Fri, 21 Aug 2020 21:22:51 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1598070171; cv=none; d=google.com; s=arc-20160816; b=ianH77QdUTSQBeYlzV8yk9U+XL4QFJAQ23ZOYAG9bjKNmEGuDUPeg5B4H1hiXWCjmX agR5lHfDm30yX0SWRHg+j/BXOyKXFf1RD1oGPRouPCS/Ea33La0N5Tvep4Rs2A5JeDWl Cp5tfUgWANa99zrOceZ96Nmo8AJZUp8X2qap6NzjxbFuiom+YeTRNS3rhgPGis63nKBh wF7GIP02E9ic+xDt5kn1L4+V1cgi8qHnEZVHDolGn0xdMNsRstlezHgv+QRnpjsBUBL/ BviiHTCzyfpOQyfx/F/9vQdxLa/bAQPjVL/BUJMLRUUmQ5KggXRTYUMIjxrX29G8H5s0 TOKg== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:sender:dkim-signature:content-transfer-encoding :mime-version:references:in-reply-to:message-id:date:subject:cc:to :from; bh=AWm7U3a8aov4PNZrSYviqR5QtvQW/uLd0HXBmgxRGZY=; b=IW88nHy/dAOIzUVOk2P0gsQJr71ysDegoN+N53q6hV7esl76UxcoIqvm+8J5RF+nP/ FKRukoVyqJ6yUs4TtAGCpVsu+f2sVd9sUIDhCfKN5Wd0Ed1Rg9NVZiRZ91Zr2moyyqAj hGat5RzkYGGz33CrDbj142IpE+F36pwos31JX4jRZSO7hVJSVIR/SpXIeb16iPZPLusL poAKe3wZucOJIuLWetpMLkdCc7WWN/rqGGjOyLi210E03neqkFkpjqFui6cwniHD0+Yp Ry7BnPFN3LSSIZQkT6FYDV5VFfWeJjvQs+KxrMtIu3tTpm5pRCi/oOu5Hc2cN6k0bz0k 1PBg== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@nvidia.com header.s=n1 header.b=ClifxiVu; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=nvidia.com Return-Path: Received: from vger.kernel.org (vger.kernel.org. [23.128.96.18]) by mx.google.com with ESMTP id dm18si2622625edb.8.2020.08.21.21.22.28; Fri, 21 Aug 2020 21:22:51 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; dkim=pass header.i=@nvidia.com header.s=n1 header.b=ClifxiVu; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=nvidia.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727084AbgHVEVX (ORCPT + 99 others); Sat, 22 Aug 2020 00:21:23 -0400 Received: from hqnvemgate26.nvidia.com ([216.228.121.65]:7900 "EHLO hqnvemgate26.nvidia.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726059AbgHVEVH (ORCPT ); Sat, 22 Aug 2020 00:21:07 -0400 Received: from hqpgpgate101.nvidia.com (Not Verified[216.228.121.13]) by hqnvemgate26.nvidia.com (using TLS: TLSv1.2, DES-CBC3-SHA) id ; Fri, 21 Aug 2020 21:20:52 -0700 Received: from hqmail.nvidia.com ([172.20.161.6]) by hqpgpgate101.nvidia.com (PGP Universal service); Fri, 21 Aug 2020 21:21:06 -0700 X-PGP-Universal: processed; by hqpgpgate101.nvidia.com on Fri, 21 Aug 2020 21:21:06 -0700 Received: from HQMAIL111.nvidia.com (172.20.187.18) by HQMAIL101.nvidia.com (172.20.187.10) with Microsoft SMTP Server (TLS) id 15.0.1473.3; Sat, 22 Aug 2020 04:21:05 +0000 Received: from hqnvemgw03.nvidia.com (10.124.88.68) by HQMAIL111.nvidia.com (172.20.187.18) with Microsoft SMTP Server (TLS) id 15.0.1473.3 via Frontend Transport; Sat, 22 Aug 2020 04:21:05 +0000 Received: from sandstorm.nvidia.com (Not Verified[10.2.94.162]) by hqnvemgw03.nvidia.com with Trustwave SEG (v7,5,8,10121) id ; Fri, 21 Aug 2020 21:21:05 -0700 From: John Hubbard To: Andrew Morton CC: Alexander Viro , Christoph Hellwig , Ilya Dryomov , Jens Axboe , Jeff Layton , , , , , , LKML , John Hubbard Subject: [PATCH 2/5] mm/gup: introduce pin_user_page() Date: Fri, 21 Aug 2020 21:20:56 -0700 Message-ID: <20200822042059.1805541-3-jhubbard@nvidia.com> X-Mailer: git-send-email 2.28.0 In-Reply-To: <20200822042059.1805541-1-jhubbard@nvidia.com> References: <20200822042059.1805541-1-jhubbard@nvidia.com> MIME-Version: 1.0 X-NVConfidentiality: public Content-Transfer-Encoding: quoted-printable Content-Type: text/plain DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nvidia.com; s=n1; t=1598070052; bh=AWm7U3a8aov4PNZrSYviqR5QtvQW/uLd0HXBmgxRGZY=; 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=ClifxiVuABBkqvc/rqX6402hmxTySQe6DZT+CO3/xTn9dndqsYA1/DERMczpJhmKX w/8FUE9ErK/3jA+GCZ1sqGBiLhg1zK1miQSti1fNYmBrsGzfSIRJRNWrpn+/ZeDWfK TDoAVUzZ0qPKq3O6BsfpzF+8d1pZMxybo8DE7gmn+fs1bAuvDstlmdsNbUGYPknySA /BbmcP7B/8lyEAKIYiK2UytD7Seeb5X4Lehc9g9Zl7nD3ix63Pbzf3Zm082f3faLgm IEDZaKiUXd/f8B1uccRquX40ku0FMN1PIKsVxxzJTPfSIIFO6Q14lYldC9vvpPg89F JlFf893Gw976g== Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@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 1983e08f5906..bee26614f430 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -1149,6 +1149,8 @@ static inline void get_page(struct page *page) page_ref_inc(page); } =20 +void pin_user_page(struct page *page); + bool __must_check try_grab_page(struct page *page, unsigned int flags); =20 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_h= ead(struct page *page, return NULL; } =20 +/* + * 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 =3D 1; + + page =3D compound_head(page); + + VM_BUG_ON_PAGE(page_ref_count(page) <=3D 0, page); + + if (hpage_pincount_available(page)) + hpage_pincount_add(page, 1); + else + refs =3D 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 * --=20 2.28.0