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 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 6ECE3C10F14 for ; Tue, 23 Apr 2019 14:16:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3C150217D9 for ; Tue, 23 Apr 2019 14:16:18 +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="VYRNSS7I" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727704AbfDWOQR (ORCPT ); Tue, 23 Apr 2019 10:16:17 -0400 Received: from mail-it1-f194.google.com ([209.85.166.194]:36524 "EHLO mail-it1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726655AbfDWOQR (ORCPT ); Tue, 23 Apr 2019 10:16:17 -0400 Received: by mail-it1-f194.google.com with SMTP id y10so385071itc.1 for ; Tue, 23 Apr 2019 07:16:17 -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=BHj8a4blDnmbXW38qdj7tJAzmZlFLW34dp2jQuPcp3Y=; b=VYRNSS7I47WY0Eicd30mUVIzdSqM+UOT+tfUg63oPNB47uPor/hGU3CGsp2VFqYIwh zywfvqKmdPyz8UCUcEhtkxfz+/rsWMTUBSngYPDZtYFEcZK2vauYb/bG1tdXamjTiejK r+V3hzGWd1FGzYXfa/2+0ocSgdW+E0hcKI+xQ= 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=BHj8a4blDnmbXW38qdj7tJAzmZlFLW34dp2jQuPcp3Y=; b=Xrki+Tm4CfiylJqw1TH2vutGE8wlserKDB42q5J2Ja7R94LdoMqMAro78VV05bn17K n/KOnhtAPCm5xKRnFxvpfG0NRgyf/TRimjQ8wdZD/lhfEBbyXvu/JljT42cqpY+3FsNQ BaNKjoHEDsjoT8UKNZMIP56f7M+nMbSsZv3nH0q+Ira89weiQ+HTP/jJt0EoSF9JzAtu jPNe95hZgRh5VaI5tEpGoIL7PJnP1Mp+AXB/rnrbtxbeR44q68KegITScYv5KdJTjTiS eI8Qj+S5Scd4H2H3Gup++r1+cA8y9OdfGypo98UnU7KE2KBT9y/8D6Ulx23zApMFA6kR SEjQ== X-Gm-Message-State: APjAAAU51XYlKeyvEfLgQ8UGKZt3s+Y+FjyY4jv/ehtyi0L9LZJsyfKs Q3szCOs/2FyA/UvJ5XGG+0bhrREERS4p2T+egxHMiA== X-Google-Smtp-Source: APXvYqwpqhU8+25NN+jG3TtbknirE4BNyz804KQn+UoEppzcVeFw5ukGns9S9sAkmMyp2kE4YX9ij8jqeHCAOEZrheI= X-Received: by 2002:a24:650d:: with SMTP id u13mr2389028itb.1.1556028976631; Tue, 23 Apr 2019 07:16:16 -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 16:16:05 +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 3:53 PM Amir Goldstein wrote: > > On Tue, Apr 23, 2019 at 4:41 PM Miklos Szeredi wrote: > > > > 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. > > > > I see. Well what we could do is set a file flag for fake path, so at least > fsnotify will be able to ignore f_path->mnt when calculating ignore mask. FMODE_NONOTIFY_MNT: like FMODE_NONOTIFY, but only affect mount marks? Thanks, Miklos