From mboxrd@z Thu Jan 1 00:00:00 1970 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=-1.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 8EDFAC2D0F4 for ; Wed, 8 Apr 2020 17:13:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6633020768 for ; Wed, 8 Apr 2020 17:13:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1586365999; bh=FoiImDp2DYzSC0NZaFstUAHqxjS8zXEz3ZgOUzfsYbI=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=uQ861+nPykLQ477qs3wIsnLdxL6dBsvI8KFsD9bijS8VB/H9Fe2UbgkqSEji9J6Kw MrIJ0UH5yIzkq0lB+HEv8SwoA7MP93KlQlVmPgp0YT+19H7aWjLWK+zRFUPnq4PXii mEHytebMSwV+Kh0pZ7+EKzHnWxnlyM9vt+lkLj/0= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730529AbgDHRNS (ORCPT ); Wed, 8 Apr 2020 13:13:18 -0400 Received: from mail-wr1-f67.google.com ([209.85.221.67]:45180 "EHLO mail-wr1-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727327AbgDHRNS (ORCPT ); Wed, 8 Apr 2020 13:13:18 -0400 Received: by mail-wr1-f67.google.com with SMTP id v5so8716225wrp.12 for ; Wed, 08 Apr 2020 10:13:14 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=PGK0QQ5iawAohJgI19o0w6WPitsBtyuTREYifWy6rnk=; b=kQK/Bwh+0qpFdFQ0xwcXj+MQ9krQFurOVk6V8npqO6OMwf88522BYVQa6n3kjAssX9 7lZH9FoKoTlpxkj9HsGpPNOyjogu8tYleo296fY8qNX6DsdNR0rmeCo2RmrM5evTagbQ vU/upI69IeISwwC/qSMgdtMvPAeOXSnnQpq1/JyMF0fKKOywfwypr6HztoEli3GA7STf Zzgbs2Hv1H9RD/UvjVNnTv8kzulbZ0Li8Kv+snbi+NrorhSKW/Rsr6V9VRbANDNbRPx/ Q2In+l0JcFe4Nji15KGGFApEo7oA3bW22gjYI+BAjiEynqkaLsT81rPMkMeau8+bqvuu jlwQ== X-Gm-Message-State: AGi0PuZ44sfkOVruPruughRkwOzY3wMLQdwXWWbp22MTnF5AWDxKoMlW UFgLjlFvjoPZWHvA5q7htek= X-Google-Smtp-Source: APiQypL2wNAUOEz6xsdGeVvjZ+Xc8BldJu40k9eRSyNvN9GmPki/87HGbWbDXEz9aBz9+p77dv/koA== X-Received: by 2002:a5d:688f:: with SMTP id h15mr985530wru.352.1586365994354; Wed, 08 Apr 2020 10:13:14 -0700 (PDT) Received: from localhost (ip-37-188-180-223.eurotel.cz. [37.188.180.223]) by smtp.gmail.com with ESMTPSA id q8sm250026wmg.22.2020.04.08.10.13.11 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 08 Apr 2020 10:13:13 -0700 (PDT) Date: Wed, 8 Apr 2020 19:13:10 +0200 From: Michal Hocko To: Linus Torvalds Cc: Peter Xu , Linux-MM , Linux Kernel Mailing List , Andrew Morton , Hillf Danton , Thomas Gleixner , Peter Zijlstra , syzbot+3be1a33f04dc782e9fd5@syzkaller.appspotmail.com Subject: Re: [PATCH] mm/gup: Let __get_user_pages_locked() return -EINTR for fatal signal Message-ID: <20200408171023.GC18914@dhcp22.suse.cz> References: <20200408155924.107722-1-peterx@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed 08-04-20 09:20:00, Linus Torvalds wrote: > On Wed, Apr 8, 2020 at 8:59 AM Peter Xu wrote: > > > > __get_user_pages_locked() will return 0 instead of -EINTR after commit > > 4426e945df588 which added extra code to allow gup detect fatal signal > > faster. Restore that behavior. > > I've applied this, but it's worth noting that > __get_user_pages_locked() can still return 0 in other situations. > > I realize that "I got zero pages" is a valid return value, but I do > wonder if we should make the rule be that a zero return value isn't > possible (return -EAGAIN or whatever if you doin't have the > EFAULT/EINTR conditions). > > So that you'd always get either an error, or a successful number of pages. > > The only case where __get_user_pages_locked() might return zero is if > you pass in a zero 'nr_pages', although I suspect even for that case > returning -EINVAL might be a better option. Yeah, that makes sense to me. And get_user_pages_locked documentation would benefit from an actual documentation as well. What we have right now is more suited to the lower level (__get_user_pages_locked) and have a high level user oriented documentation. -- Michal Hocko SUSE Labs