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=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED autolearn=ham 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 0D103C10F14 for ; Tue, 23 Apr 2019 13:41:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BB93D214AE for ; Tue, 23 Apr 2019 13:41:36 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="key not found in DNS" (0-bit key) header.d=szeredi.hu header.i=@szeredi.hu header.b="qFvjx7qO" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727776AbfDWNlf (ORCPT ); Tue, 23 Apr 2019 09:41:35 -0400 Received: from mail-it1-f195.google.com ([209.85.166.195]:38879 "EHLO mail-it1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727703AbfDWNlf (ORCPT ); Tue, 23 Apr 2019 09:41:35 -0400 Received: by mail-it1-f195.google.com with SMTP id q19so149815itk.3 for ; Tue, 23 Apr 2019 06:41:35 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=szeredi.hu; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=XTKmZXBJqYBFcSf7Cq045bmKpcs3TsR+il0/ALSK2p8=; b=qFvjx7qO62PGEyMvUR556Gw/WIlWRceC0G6wMSNmzLStcSQm5SiFXEbdVok+A+T3DH ZuF1i3rydWJrMZhULFptIYU0HPXP6xP5o0CX86bsXn7lvbvdNzKHCGN8E7jH4w5Ogi44 eh+vWp8qBayeNeLI4xlGZ5BRnTdioZzeNFNj4= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=XTKmZXBJqYBFcSf7Cq045bmKpcs3TsR+il0/ALSK2p8=; b=k539u9VPhSV7fxVdUPvGFKexkP0ykC1QP6PcMbWffeVYjx30rU05gkHd6jZ5CJ53g8 IAypdxEdnfOkuEakDPZ3SOtxepaGsRWOpfKyQB0ZzkiaqPY68SShUrJyGOM2o0MURWBd 65W/w24ZuJOFjqjE9m2QqblrDpxPtKiLbvx0OOEVbCyIC2uRtvI1XQ6PcoQ8H3K1NTZQ Qb0TaXI6v/hmqvtfLk+Z+wjJFp1Dyo6JvjA+ELRuaZVzYCeCZL5sADmBtYAISxeeKRlS dTgkFieEjLbdI1YF4Jt6YxujA5FUu9ON70avaU0zLNAwi522DI2CmjdF0t3cTw810eZa nH3g== X-Gm-Message-State: APjAAAVanlnEMa+u7Pcf8plkbcXl9bQ+kIN9IV0bIAvyda7xq2TXbLNL iLdqvpNBRjB9O2cxOhT3zHcw6Sdx1/6D8QSorzZNbA== X-Google-Smtp-Source: APXvYqyGWt8GpiCxUztKSiB9eS9gSjI+4rLbo591GWX+7kXMJay5eF2hEXuYhgcttmL949arwYCf/SptFM8ByRT5A/E= X-Received: by 2002:a24:1342:: with SMTP id 63mr1971102itz.69.1556026894734; Tue, 23 Apr 2019 06:41:34 -0700 (PDT) MIME-Version: 1.0 References: <20190423065024.12695-1-jencce.kernel@gmail.com> In-Reply-To: From: Miklos Szeredi Date: Tue, 23 Apr 2019 15:41:23 +0200 Message-ID: Subject: Re: [PATCH] ovl: add RWF_NONITIFY flag to skip wrong duplicate fanotify event To: Amir Goldstein Cc: Murphy Zhou , overlayfs , linux-fsdevel Content-Type: text/plain; charset="UTF-8" Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Tue, Apr 23, 2019 at 2:44 PM Amir Goldstein wrote: > > On Tue, Apr 23, 2019 at 2:40 PM Miklos Szeredi wrote: > > > > On Tue, Apr 23, 2019 at 1:00 PM Amir Goldstein wrote: > > > > > > On Tue, Apr 23, 2019 at 9:51 AM Murphy Zhou wrote: > > > > > > > > Overlays ovl_iter_write calls vfs_iter_write to write on real file, > > > > in which calls fsnotify_modify on this change, however vfs_write also > > > > calls fsnotify_modify after ovl_iter_write. The first notification > > > > sent by vfs_iter_write grabs marks from upper inode and overlay mnt, > > > > because of its fake path. The second one sent by vfs_write grabs marks > > > > from ovl inode and ovl mnt. > > > > > > > > LTP fanotify06 add modify mark for mnt point, then add ignore modify > > > > mask on testfile, then truncate and write the file. Because the ignore > > > > mask is marked on ovl inode, not the upper inode, the first event is not > > > > masked like the second one. So we get a modification event even with a > > > > mask on the file. > > > > > > Care to extend fanotify06 in a similar manner to the way readahead02 > > > was extended to test overlay test case regardless of the base LTP filesystem? > > > > > > > > > > > Proposing fixing this by add a new RWF flag to skip fsnotify on this IO. > > > > vfs_iter_write used by ovl can use this flag to skip one duplicate event. > > > > > > > > > > This fix is wrong for several reasons: > > > - It exports RWF_NONOTIFY to uapi > > > - It will cause no events at all when overlay writes to file even when user > > > requested events on upper inode > > > > > > Please try attached patch. > > > > Would be nice, but until mmap stops using realfile this isn't a good solution. > > > > Sigh! I figured there was a catch... > Will it be ok if fake path used a cloned private mount of overlay mount? So the reason we have the fake path is e.g. /proc/$$/maps. That can only work with the original mount, AFAICS. We could have one realfile for regular I/O and a separate one for mmap but that would increase complexity as well as resource use, so I'm not quite sure if that's the right solution. Thanks, Miklos