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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, 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 B09DEC7618B for ; Tue, 23 Jul 2019 10:42:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 939CD22512 for ; Tue, 23 Jul 2019 10:42:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732471AbfGWKmt (ORCPT ); Tue, 23 Jul 2019 06:42:49 -0400 Received: from mail-qt1-f194.google.com ([209.85.160.194]:46772 "EHLO mail-qt1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729836AbfGWKmt (ORCPT ); Tue, 23 Jul 2019 06:42:49 -0400 Received: by mail-qt1-f194.google.com with SMTP id h21so41331294qtn.13 for ; Tue, 23 Jul 2019 03:42:48 -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=N4xK5veZG09uUkAaPdHZto+xy99VCECeBtRkb6sAB/w=; b=OyqEscqSIWL2Ugn6++0ThaejYaPcfl/dP0fdn5hCqlzc2t8pfoz4MlOM+Xk+asUoct FiUm+3v4NyN8dWanQRZOHvuh5rQJ4QISW2CWyzR9a5Tz+JBtFJarIIELRC4BbB06kQ++ RWzcnK1JCTLL4xUeQVW2vm0rsnj/lhFeXdnqs/NnqZiJ+5pXfeqZWPu5e+FGNR5XRulB XixqlGZphAgJK5t/hATXnZ/7+a8ulp2QFZG4AQi7Z2Dj4gIDbeccDS6mayPtAfnSoDHV LAmH084ZChCjHBJz9D624JIk5SD3X8rsmTipwmIKwKRR5s8o5CvjTnS77zAlqHohoxau RXfQ== X-Gm-Message-State: APjAAAVRAtAwYI6/xl3hOkzOVR80PdKtKDq3JCq97XPIGgQtAcjdzNqZ cSvBV7UIVROqrtZl0AHKiJt4Dw== X-Google-Smtp-Source: APXvYqyaExRlYw/QlDd/NWuqasay2jAYk3JOBnWzJfjESy3cklpZQkiKPy3zfhsnVUYaS/Q/QI1fjQ== X-Received: by 2002:a0c:d4d0:: with SMTP id y16mr52541534qvh.191.1563878568268; Tue, 23 Jul 2019 03:42:48 -0700 (PDT) Received: from redhat.com (bzq-79-181-91-42.red.bezeqint.net. [79.181.91.42]) by smtp.gmail.com with ESMTPSA id b7sm18536990qtt.38.2019.07.23.03.42.41 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Tue, 23 Jul 2019 03:42:47 -0700 (PDT) Date: Tue, 23 Jul 2019 06:42:38 -0400 From: "Michael S. Tsirkin" To: Jason Wang Cc: syzbot , aarcange@redhat.com, akpm@linux-foundation.org, christian@brauner.io, davem@davemloft.net, ebiederm@xmission.com, elena.reshetova@intel.com, guro@fb.com, hch@infradead.org, james.bottomley@hansenpartnership.com, jglisse@redhat.com, keescook@chromium.org, ldv@altlinux.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-parisc@vger.kernel.org, luto@amacapital.net, mhocko@suse.com, mingo@kernel.org, namit@vmware.com, peterz@infradead.org, syzkaller-bugs@googlegroups.com, viro@zeniv.linux.org.uk, wad@chromium.org Subject: Re: WARNING in __mmdrop Message-ID: <20190723062842-mutt-send-email-mst@kernel.org> References: <0000000000008dd6bb058e006938@google.com> <000000000000964b0d058e1a0483@google.com> <20190721044615-mutt-send-email-mst@kernel.org> <75c43998-3a1c-676f-99ff-3d04663c3fcc@redhat.com> <20190722035657-mutt-send-email-mst@kernel.org> <20190723010156-mutt-send-email-mst@kernel.org> <124be1a2-1c53-8e65-0f06-ee2294710822@redhat.com> <20190723032800-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: linux-parisc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-parisc@vger.kernel.org On Tue, Jul 23, 2019 at 04:42:19PM +0800, Jason Wang wrote: > > So how about this: do exactly what you propose but as a 2 patch series: > > start with the slow safe patch, and add then return uaddr optimizations > > on top. We can then more easily reason about whether they are safe. > > > If you stick, I can do this. So I definitely don't insist but I'd like us to get back to where we know existing code is very safe (if not super fast) and optimizing from there. Bugs happen but I'd like to see a bisect giving us "oh it's because of XYZ optimization" and not the general "it's somewhere within this driver" that we are getting now. Maybe the way to do this is to revert for this release cycle and target the next one. What do you think? -- MST