From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S1751645AbdIOWM7 (ORCPT <rfc822;w@1wt.eu>);
        Fri, 15 Sep 2017 18:12:59 -0400
Received: from imap.thunk.org ([74.207.234.97]:33098 "EHLO imap.thunk.org"
        rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
        id S1751184AbdIOWM5 (ORCPT <rfc822;linux-kernel@vger.kernel.org>);
        Fri, 15 Sep 2017 18:12:57 -0400
Date: Fri, 15 Sep 2017 18:12:38 -0400
From: "Theodore Ts'o" <tytso@mit.edu>
To: Jaegeuk Kim <jaegeuk@kernel.org>
Cc: Al Viro <viro@ZenIV.linux.org.uk>, linux-kernel@vger.kernel.org,
        linux-fsdevel@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net
Subject: Re: [PATCH] vfs: introduce UMOUNT_WAIT which waits for umount
 completion
Message-ID: <20170915221238.js6elr5jmj4mgt67@thunk.org>
Mail-Followup-To: Theodore Ts'o <tytso@mit.edu>,
        Jaegeuk Kim <jaegeuk@kernel.org>, Al Viro <viro@ZenIV.linux.org.uk>,
        linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
        linux-f2fs-devel@lists.sourceforge.net
References: <20170913234437.GO5426@ZenIV.linux.org.uk>
 <20170914011048.GA47448@jaegeuk-macbookpro.roam.corp.google.com>
 <20170914013017.GP5426@ZenIV.linux.org.uk>
 <20170914183723.GA17131@ZenIV.linux.org.uk>
 <20170914191447.GA9428@jaegeuk-macbookpro.roam.corp.google.com>
 <20170915001939.GA20096@jaegeuk-macbookpro.roam.corp.google.com>
 <20170915020607.GW5426@ZenIV.linux.org.uk>
 <20170915034518.GB20096@jaegeuk-macbookpro.roam.corp.google.com>
 <20170915042137.GX5426@ZenIV.linux.org.uk>
 <20170915184433.GA32008@jaegeuk-macbookpro.roam.corp.google.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20170915184433.GA32008@jaegeuk-macbookpro.roam.corp.google.com>
User-Agent: NeoMutt/20170609 (1.8.3)
X-SA-Exim-Connect-IP: <locally generated>
X-SA-Exim-Mail-From: tytso@thunk.org
X-SA-Exim-Scanned: No (on imap.thunk.org); SAEximRunCond expanded to false
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Fri, Sep 15, 2017 at 11:44:33AM -0700, Jaegeuk Kim wrote:
> 
> So, I digged it in more detail, and found, in drivers/android/binder.c [1],
> - binder_ioctl()
>  - create a kernel thread
>  - zombie_cleanup_check()
>   - binder_defer_work()
>     - queue_work(..., &binder_deferred_work);
> 
> - binder_deferred_func()
>  - binder_clear_zombies()
>   - binder_proc_clear_zombies()
>    - put_files_struct()
>     - close_files()
>      - filp_close()
>       - fput()
> 
> It seems binder holds some proc files.

If binder was holding some files open, then umount should have failed
with EBUSY, no?

Does Android use mount namespaces at all?

					- Ted