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=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,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 C93D7C7618B for ; Tue, 23 Jul 2019 10:42:54 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id A2C5A22512 for ; Tue, 23 Jul 2019 10:42:54 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="Q8lAya1M" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A2C5A22512 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=Yk43b1I+BGxeYxSc0dfw5PhbNb9WGk6gsn2Z3s1sgwc=; b=Q8lAya1MElSGoY 5nK17O9SN5JGa9kGXKrwomVmsAbEnqlaTPmYMCmLFj0qNGF7kOpZVgC6f85gwwIVS4og2y9exikBF xtjj/4r6xMVF1RqrkDSICB0NJziBOFStvo30N5a/gUqaiye1/d2FK3z7nZ8UNw0mqcN6j41sxM3vQ HN+wOSHbJtG4COkE1+bzX0KOe5bY8S79oGRW5DB1oCqxCCND1M+KrZ4gcMA45rp0X9mB0GmgaBrwh yhKj3kN9WPzgwU2XjtQFSH+nx/ODb52UMaDi7l0RrcWPa7DE418WijBt7KPIO+grBq3va6t8We4ZX NTtsBWgbQUYBk0LlCuDw==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92 #3 (Red Hat Linux)) id 1hpsFx-0005wq-N9; Tue, 23 Jul 2019 10:42:53 +0000 Received: from mail-qt1-f195.google.com ([209.85.160.195]) by bombadil.infradead.org with esmtps (Exim 4.92 #3 (Red Hat Linux)) id 1hpsFu-0005jN-5s for linux-arm-kernel@lists.infradead.org; Tue, 23 Jul 2019 10:42:51 +0000 Received: by mail-qt1-f195.google.com with SMTP id y26so41394353qto.4 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=Cr3MRyKzduTcJmo/kzFx3Pv6Rz+ednvTAxhzFdlNqd6V6OsB6jhNLrPWNgDBd5Pfo8 oU0BpI5yh6MXiaJtYkCqPJyrOpe9qu97uiHplSgDXJbgcgfDtq3KOBtloeT3B/dNI5e2 CMhvJr/btvZC3HPmeOXS+H3626YaZJeG/thdZZwCa5/HZRq04D5BSl/PYS+0ROTJXwjg yvS4MZZ5Hp50TToptcbQ74CX+Xj1JbVCbZ4Q01ZM4LXtlLHUt7d5qH/UQz7aoEytllAB 9o5kto/27SAt3Ws6S9JsG3E8gQXHRFwDxS6AmCwRgSxhJ1BQ65bpzOIw3pSBRiG6svCn XwZQ== X-Gm-Message-State: APjAAAWNv3vDVM3GspQrqPaTi9/xYtPIOk5kmzHoBSOOfsC1DeyZVivf //L10vaZ1XAeM5YKu+GHKK9f1Q== 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 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-Disposition: inline In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190723_034250_249818_75D1EC3C X-CRM114-Status: GOOD ( 10.14 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: mhocko@suse.com, peterz@infradead.org, ldv@altlinux.org, james.bottomley@hansenpartnership.com, linux-mm@kvack.org, namit@vmware.com, mingo@kernel.org, elena.reshetova@intel.com, keescook@chromium.org, aarcange@redhat.com, davem@davemloft.net, hch@infradead.org, christian@brauner.io, syzbot , syzkaller-bugs@googlegroups.com, jglisse@redhat.com, viro@zeniv.linux.org.uk, linux-arm-kernel@lists.infradead.org, wad@chromium.org, linux-parisc@vger.kernel.org, linux-kernel@vger.kernel.org, luto@amacapital.net, ebiederm@xmission.com, akpm@linux-foundation.org, guro@fb.com Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.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 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel