From patchwork Fri Aug 27 16:49:24 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andreas Gruenbacher X-Patchwork-Id: 12462399 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=-16.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 6395DC432BE for ; Fri, 27 Aug 2021 16:51:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4A2CD60EE5 for ; Fri, 27 Aug 2021 16:51:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232844AbhH0Qwj (ORCPT ); Fri, 27 Aug 2021 12:52:39 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:20007 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234297AbhH0QwT (ORCPT ); Fri, 27 Aug 2021 12:52:19 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1630083089; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=zltTk4Y5c4tY2vgCMzhETo7fDPnjlrUk0T/NxlEENxc=; b=W3xUo7qDrVJjUiYfwpwEw2VUFCqAkvmyHFkkPIMeWzhuK6eJhyJzxeQDWJ2Y+E/6S5ERbK SltydVGiyv9kBMmHEZXjsFWRBcDX4j1pIJ4o2oF03HJU/bIsd1EEY3oIGxvzJwNgN4GbLd jr8+CVeAT6c5F9yPneTgjV8Iv1J/ApY= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-42-y3UaVDVzPnqtm79cLGJbsQ-1; Fri, 27 Aug 2021 12:51:28 -0400 X-MC-Unique: y3UaVDVzPnqtm79cLGJbsQ-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id AED901009E28; Fri, 27 Aug 2021 16:51:26 +0000 (UTC) Received: from max.com (unknown [10.40.194.206]) by smtp.corp.redhat.com (Postfix) with ESMTP id F364B60C81; Fri, 27 Aug 2021 16:51:17 +0000 (UTC) From: Andreas Gruenbacher To: Linus Torvalds , Alexander Viro , Christoph Hellwig , "Darrick J. Wong" Cc: Jan Kara , Matthew Wilcox , cluster-devel@redhat.com, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, ocfs2-devel@oss.oracle.com, Andreas Gruenbacher Subject: [PATCH v7 17/19] gup: Introduce FOLL_NOFAULT flag to disable page faults Date: Fri, 27 Aug 2021 18:49:24 +0200 Message-Id: <20210827164926.1726765-18-agruenba@redhat.com> In-Reply-To: <20210827164926.1726765-1-agruenba@redhat.com> References: <20210827164926.1726765-1-agruenba@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org Introduce a new FOLL_NOFAULT flag that causes get_user_pages to return -EFAULT when it would otherwise trigger a page fault. This is roughly similar to FOLL_FAST_ONLY but available on all architectures, and less fragile. Signed-off-by: Andreas Gruenbacher --- include/linux/mm.h | 3 ++- mm/gup.c | 4 +++- 2 files changed, 5 insertions(+), 2 deletions(-) diff --git a/include/linux/mm.h b/include/linux/mm.h index 7ca22e6e694a..958246aa343f 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -2850,7 +2850,8 @@ struct page *follow_page(struct vm_area_struct *vma, unsigned long address, #define FOLL_FORCE 0x10 /* get_user_pages read/write w/o permission */ #define FOLL_NOWAIT 0x20 /* if a disk transfer is needed, start the IO * and return without waiting upon it */ -#define FOLL_POPULATE 0x40 /* fault in page */ +#define FOLL_POPULATE 0x40 /* fault in pages (with FOLL_MLOCK) */ +#define FOLL_NOFAULT 0x80 /* do not fault in pages */ #define FOLL_HWPOISON 0x100 /* check page is hwpoisoned */ #define FOLL_NUMA 0x200 /* force NUMA hinting page fault */ #define FOLL_MIGRATION 0x400 /* wait for page to replace migration entry */ diff --git a/mm/gup.c b/mm/gup.c index 03ab03b68dc7..69056adcc8c9 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -932,6 +932,8 @@ static int faultin_page(struct vm_area_struct *vma, /* mlock all present pages, but do not fault in new pages */ if ((*flags & (FOLL_POPULATE | FOLL_MLOCK)) == FOLL_MLOCK) return -ENOENT; + if (*flags & FOLL_NOFAULT) + return -EFAULT; if (*flags & FOLL_WRITE) fault_flags |= FAULT_FLAG_WRITE; if (*flags & FOLL_REMOTE) @@ -2857,7 +2859,7 @@ static int internal_get_user_pages_fast(unsigned long start, if (WARN_ON_ONCE(gup_flags & ~(FOLL_WRITE | FOLL_LONGTERM | FOLL_FORCE | FOLL_PIN | FOLL_GET | - FOLL_FAST_ONLY))) + FOLL_FAST_ONLY | FOLL_NOFAULT))) return -EINVAL; if (gup_flags & FOLL_PIN)