From owner-freebsd-arch@freebsd.org Fri Sep 15 10:49:19 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 1409EE0D7EE; Fri, 15 Sep 2017 10:49:19 +0000 (UTC) (envelope-from etnapierala@gmail.com) Received: from mail-ua0-x22a.google.com (mail-ua0-x22a.google.com [IPv6:2607:f8b0:400c:c08::22a]) (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 BCCC029EE; Fri, 15 Sep 2017 10:49:18 +0000 (UTC) (envelope-from etnapierala@gmail.com) Received: by mail-ua0-x22a.google.com with SMTP id t5so1033493uad.13; Fri, 15 Sep 2017 03:49:18 -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=JvUxFc3iQf2tK20/Xg7cXWHxAE9QNx105L4hLj9hTJU=; b=tBeEV1zKSsrO7PT47ysShzYNIolFkAW0CfJylCSFmnEhDY6ZT9kgNiz2XR0l48c4Ts Bmv5hig88Eb9MiSxhSNF2xmtEsEH5AsoZmUsx5O6HdLMcOd9dp3nBDJmDY90mB9OG6TJ KbnTBQVHOGsT+bIYJR3zis1TH1y2gkgE6BAkjjJ1jKCywNr6YwUde/tpZKBld1Lw23bM PZWKNDWyGl+nc9uKKZJjkFuAplB27knxVh9cTJy6qr1Yfbw/7C8665qCheO6Cpw3Ymuf iy1RVYuvWYvo3L1KvvcpSmHEscbMhRubOmNAJc9HjgXDEboebCSHRwpYMSohMxTtu58M qMuw== 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=JvUxFc3iQf2tK20/Xg7cXWHxAE9QNx105L4hLj9hTJU=; b=V2ONm50Kj2WHgWwlSXwq8YLS2nl6pEgpBfBCyNUUsgdN6F/v3OovJjV9UMf8K+xAty IAXSp15WeqvyDc80PuJda4AdzUVgaFbYFVHcwyjTaLu9svO/od7+hIHuNBHjItzRBEYn NsMTtBEZKAD8/eUrTRt8eBqp6V1FNUjdL8RTchSDQ8R9UazXmKZ/sMGN6srHm+/OEfys ZKncfxKtxRMjpZovSHmVFxQaeniKivzFeKMcQStL+frfaXk1sTXXRT8mQaD8xAEFFQFB 5lZylaB703Dp66/Zk+hsMh2UkluJIvpa+Cyc+JYd0e+46u4beXy/EG7k9nBCN9VZhts+ qcHw== X-Gm-Message-State: AHPjjUgqlD46efSK1UR/oACLLeCSz97JF8xanz+1SINtbdxZVce+58V/ JKyqxqJmNx0XtwOAcbzqTiv8ytXyAKhCOnB1fRw= X-Google-Smtp-Source: AOwi7QAKe5oLEoNiGKpgmJKxqY5j9fk7JoVcuwqj+WtI4dflqwHlboZ0ayKkTBSAuTTquJTl41gK506818mwW6KPt78= X-Received: by 10.176.83.123 with SMTP id y56mr21175614uay.172.1505472557839; Fri, 15 Sep 2017 03:49:17 -0700 (PDT) MIME-Version: 1.0 Sender: etnapierala@gmail.com Received: by 10.159.51.232 with HTTP; Fri, 15 Sep 2017 03:49:17 -0700 (PDT) In-Reply-To: <20170915103037.GM78693@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> From: Edward Napierala Date: Fri, 15 Sep 2017 11:49:17 +0100 X-Google-Sender-Auth: wZ_JDot4INtpYyYVBEu9HHbFkw4 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 10:49:19 -0000 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. 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.