From patchwork Fri Apr 29 10:42:14 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg Kroah-Hartman X-Patchwork-Id: 568524 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1CB9DC433FE for ; Fri, 29 Apr 2022 10:45:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238217AbiD2KsT (ORCPT ); Fri, 29 Apr 2022 06:48:19 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59998 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1354933AbiD2KsK (ORCPT ); Fri, 29 Apr 2022 06:48:10 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 78017C1C9D; Fri, 29 Apr 2022 03:43:26 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 00E6160B06; Fri, 29 Apr 2022 10:43:26 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0B0ECC385A7; Fri, 29 Apr 2022 10:43:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1651229005; bh=fCJxO62DgJ7IYqm6IbepVM8R/1npYr0yMSg8doMFr7Y=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=01FZ53fvJvI4+eSgbZIO6WWgAATmgPMHh1QmfKXcuGO22iQwZH9TSxRTns/Rp87IQ 4qH+ZxvPNvodKs7BVdklMerd/3ItUshjB4dbrprf3g4dw/HoZwOLdOfBQrnG+WVkbE 1geurPD5XCQ6n8DGJ4Kc1vb/nBBA97K1sNNlsL/M= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Greg Kroah-Hartman , Andreas Gruenbacher , Anand Jain Subject: [PATCH 5.15 27/33] gup: Introduce FOLL_NOFAULT flag to disable page faults Date: Fri, 29 Apr 2022 12:42:14 +0200 Message-Id: <20220429104053.124854665@linuxfoundation.org> X-Mailer: git-send-email 2.36.0 In-Reply-To: <20220429104052.345760505@linuxfoundation.org> References: <20220429104052.345760505@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Andreas Gruenbacher commit 55b8fe703bc51200d4698596c90813453b35ae63 upstream 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 Signed-off-by: Anand Jain Signed-off-by: Greg Kroah-Hartman --- include/linux/mm.h | 3 ++- mm/gup.c | 4 +++- 2 files changed, 5 insertions(+), 2 deletions(-) --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -2858,7 +2858,8 @@ struct page *follow_page(struct vm_area_ #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 */ --- a/mm/gup.c +++ b/mm/gup.c @@ -943,6 +943,8 @@ static int faultin_page(struct vm_area_s /* 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) @@ -2868,7 +2870,7 @@ static int internal_get_user_pages_fast( 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)