From patchwork Tue Nov 2 12:29:43 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andreas Gruenbacher X-Patchwork-Id: 12598783 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 75FD9C4332F for ; Tue, 2 Nov 2021 12:31:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5A28060C51 for ; Tue, 2 Nov 2021 12:31:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231927AbhKBMeX (ORCPT ); Tue, 2 Nov 2021 08:34:23 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:43085 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231920AbhKBMeU (ORCPT ); Tue, 2 Nov 2021 08:34:20 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1635856305; 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=YU9rEXEndLCwBxiEdTyNgcsUGIjKGRnQTEaZLBH6B0o=; b=FNkRHEYdAhithI5JVzxhvN91qv64dIG9vyoMCf84Rng+nigu+giWri+U3jM45HW23hFmK3 tLx9DC5YMN4OhA5Y063vu1Gqob5fxBCxqnNqdYMmhTiJIj9bfmA/fGGSDoplZTZ54/gw8c eJWFWO6ZmsHqv8g/X9eoLWm2kFMXN+A= 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-430-pjBKn9bONYemierX2tUiJA-1; Tue, 02 Nov 2021 08:31:41 -0400 X-MC-Unique: pjBKn9bONYemierX2tUiJA-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id C78F98B4274; Tue, 2 Nov 2021 12:31:30 +0000 (UTC) Received: from max.localdomain (unknown [10.40.195.95]) by smtp.corp.redhat.com (Postfix) with ESMTP id 97D36652AC; Tue, 2 Nov 2021 12:31:22 +0000 (UTC) From: Andreas Gruenbacher To: cluster-devel@redhat.com Cc: Linus Torvalds , Catalin Marinas , Alexander Viro , Christoph Hellwig , "Darrick J. Wong" , Paul Mackerras , Jan Kara , Matthew Wilcox , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, ocfs2-devel@oss.oracle.com, kvm-ppc@vger.kernel.org, linux-btrfs@vger.kernel.org, Andreas Gruenbacher Subject: [PATCH v9 15/17] gup: Introduce FOLL_NOFAULT flag to disable page faults Date: Tue, 2 Nov 2021 13:29:43 +0100 Message-Id: <20211102122945.117744-16-agruenba@redhat.com> In-Reply-To: <20211102122945.117744-1-agruenba@redhat.com> References: <20211102122945.117744-1-agruenba@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@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 73a52aba448f..2f0e6b9f8f3b 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -2851,7 +2851,8 @@ 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 795f15c410cc..e1c7e4bde11f 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -918,6 +918,8 @@ 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) @@ -2843,7 +2845,7 @@ 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)