From owner-freebsd-arch@freebsd.org Fri Sep 15 11:31:07 2017 Return-Path: Delivered-To: freebsd-arch@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 77BF2E0F8FB; Fri, 15 Sep 2017 11:31:07 +0000 (UTC) (envelope-from etnapierala@gmail.com) Received: from mail-ua0-x229.google.com (mail-ua0-x229.google.com [IPv6:2607:f8b0:400c:c08::229]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority G2" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 299D33F35; Fri, 15 Sep 2017 11:31:07 +0000 (UTC) (envelope-from etnapierala@gmail.com) Received: by mail-ua0-x229.google.com with SMTP id 72so1070216uas.8; Fri, 15 Sep 2017 04:31:07 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:sender:in-reply-to:references:from:date:message-id :subject:to:cc; bh=BCI+uCZ99PDTwjj4fnECwhYjMbmHlI4kV7UO85WAj8k=; b=U0vg7NkxyyqeGXIDr/C6/jmM6AJ5gVozWuK9AgDgydTm6oHMOZiKNM4eVkfPnqtw96 ahfiOjiFXo+n35bbiJufPvHGgCO35W/el8DTt7syEWMmmhuYgc1A9KA8iBXnk+PcY0wH lqc6z8XdwC/Yx5DuM8GP8DHUqejEyExjexGrW+8J6Lwblkv59vT4O/XsJrS8SCEzpQNt QaPLHpbPWBYq8rMr/cnS0M74x1cyiLoewU6DLrFC3C+kZ+ooU2KKK9VRaw7AhJ/CyYQx UUnlxAMGeta+eczBC6nx+WjFVl1AcGIAlaStYXQnBdIo01i9jPTmIzngkRpozi5koJG0 F0eQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:sender:in-reply-to:references:from :date:message-id:subject:to:cc; bh=BCI+uCZ99PDTwjj4fnECwhYjMbmHlI4kV7UO85WAj8k=; b=hL+wHv79DnMU3zQFG9+BJALOlB9x/m1CAJkYow0jz8HUh6c74eZuJfR+XADos/YhiT 97CwOKNgjkHrqURfNGOQ+MKU+4hlMHyA+yLv/+ESrZsNPazVkZagW6/OqJHxakjOvR9t /I+5O9Dycog+MRZ59IUN7BEEoVUYdEa4m2LTvfIbeJlufdjtl+9EmczU56s7eE/rm1UR /IR6uXSZmmMCGMeEtsGN7m1adCmUkAQ2WFd0L7wENSMrStEDSomA2sxb19sc8QZp+5No TMaf/P7J8fnrCpt4U1ZRYiSSBqmOCyxhJa8qzXgyyjgXL/LJIRB4us/LgkK0trrAJllS IEJQ== X-Gm-Message-State: AHPjjUiM2BPESQUGSOPP6JSuHolU1n4MZSyMoJ1KZqsQGYMkF4YH/Xfn GckE8S7Z5Bpbp/w+WMYibtQ4g0y4n9H0t9hy1bQ= X-Google-Smtp-Source: ADKCNb5aTm0GnEozTU1lPnkNjCT3fdmbp/nT0ji7/w9OI6+wGuezGPLbtCkGeU02divGOZokZ3ZkYIurzFdL7sIU3W8= X-Received: by 10.176.92.111 with SMTP id a47mr21213593uag.111.1505475065951; Fri, 15 Sep 2017 04:31:05 -0700 (PDT) MIME-Version: 1.0 Sender: etnapierala@gmail.com Received: by 10.159.51.232 with HTTP; Fri, 15 Sep 2017 04:31:05 -0700 (PDT) In-Reply-To: <20170915110033.GO78693@kib.kiev.ua> References: <134c7c6e-f4f1-ef38-cc50-0e56c27c9fb8@FreeBSD.org> <201709150314.v8F3Ea6B085072@chez.mckusick.com> <20170915092001.GK78693@kib.kiev.ua> <20170915103037.GM78693@kib.kiev.ua> <20170915110033.GO78693@kib.kiev.ua> From: Edward Napierala Date: Fri, 15 Sep 2017 12:31:05 +0100 X-Google-Sender-Auth: MfR-gur5i6VTgT8RqaOUE7DyMKA Message-ID: Subject: Re: mount / unmount and mountcheckdirs() To: Konstantin Belousov Cc: Kirk McKusick , freebsd-fs , Andriy Gapon , "freebsd-arch@freebsd.org" Content-Type: text/plain; charset="UTF-8" X-Content-Filtered-By: Mailman/MimeDel 2.1.23 X-BeenThere: freebsd-arch@freebsd.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: Discussion related to FreeBSD architecture List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 15 Sep 2017 11:31:07 -0000 2017-09-15 12:00 GMT+01:00 Konstantin Belousov : > On Fri, Sep 15, 2017 at 11:49:17AM +0100, Edward Napierala wrote: > > 2017-09-15 11:30 GMT+01:00 Konstantin Belousov : > > > > > On Fri, Sep 15, 2017 at 11:08:31AM +0100, Edward Napierala wrote: > > > > 2017-09-15 10:20 GMT+01:00 Konstantin Belousov >: > > > > > I believe that the current autofs does not allow a process to get > into > > > > > this situation at all. > > > > > > > > > > > > > It does. For example: > > > > > > > > [trasz@v2:~]% cd /media/md0 > > > > [trasz@v2:/media/md0]% mount > > > > /dev/ada0s1a on / (ufs, local, noatime, journaled soft-updates) > > > > devfs on /dev (devfs, local, multilabel) > > > > map -hosts on /net (autofs) > > > > map -media on /media (autofs) > > > > [trasz@v2:/media/md0]% ls > > > > [trasz@v2:/media/md0]% mount > > > > /dev/ada0s1a on / (ufs, local, noatime, journaled soft-updates) > > > > devfs on /dev (devfs, local, multilabel) > > > > map -hosts on /net (autofs) > > > > map -media on /media (autofs) > > > > /dev/md0 on /media/md0 (ufs, local, noatime, nosuid, automounted) > > > > > > > > Getting rid of mountcheckdirs() in the unmount path should be fine, I > > > think. > > > How the example proves that mountcheckdirs() can be removed ? > > > > > > In the unmount path? It doesn't; I just don't think autofs would be > > affected, > > since having a current working directory in a mountpoint prevents the > > unmount > > (unless it's forced). > > > > In the mount path? See below. > > > > > > > How can > > > we see which directory content was printed by ls, the covered or > mounted ? > > > > > > > Well, it would be pretty useless if you got the covered directory. > This is exactly what is being discussed. > > > But ok, here's > > a better example, one that actually shows that: > > > > [trasz@v2:/media/md0]% mount > > /dev/ada0s1a on / (ufs, local, noatime, journaled soft-updates) > > devfs on /dev (devfs, local, multilabel) > > map -hosts on /net (autofs) > > map -media on /media (autofs) > > [trasz@v2:/media/md0]% ls -al > > total 9 > > drwxr-xr-x 3 root wheel 512 Sep 10 10:16 . > > drwxr-xr-x 3 root wheel 512 Sep 8 11:42 .. > > drwxrwxr-x 2 root operator 512 Sep 10 10:16 .snap > > [trasz@v2:/media/md0]% mount > > /dev/ada0s1a on / (ufs, local, noatime, journaled soft-updates) > > devfs on /dev (devfs, local, multilabel) > > map -hosts on /net (autofs) > > map -media on /media (autofs) > > /dev/md0 on /media/md0 (ufs, local, noatime, nosuid, automounted) > > > > Notice the .snap/ directory; it's an empty UFS filesystem. > And the .snap is from the /dev/md0 volume, right ? > Yes. > If yes, then this demonstration indeed proves that autofs behaves as > intended on mount. > Exactly. And, from what I understand, that would break if mountcheckdirs() got removed from the mount path.