linux-kernel - Re: mount notification question

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Message-ID: <AANLkTi=h633N2toWEHqwubVf8Hd21==+4Or7h=35d+Kr@mail.gmail.com>
Date:	Fri, 6 Aug 2010 09:44:02 +0200
From:	Kay Sievers <kay.sievers@...y.org>
To:	Daniel Lezcano <daniel.lezcano@...e.fr>
Cc:	Chris Friesen <cfriesen@...tel.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: mount notification question

On Fri, Aug 6, 2010 at 03:07, Daniel Lezcano <daniel.lezcano@...e.fr> wrote:
> On 08/04/2010 08:41 PM, Chris Friesen wrote:
>> On 08/02/2010 03:12 PM, Daniel Lezcano wrote:
>>> is there a way to be notified when a mount occurs on the system ?
>>
>> Have you looked on google?  The link is a bit misleading but they do
>> give a way to do it (not using inotify).
>>
>> http://stackoverflow.com/questions/1113176/how-could-i-detect-when-a-directory-is-mounted-with-inotify
>
> Thanks a lot for the pointer. I am not sure this solution will work, because
> it is inadequate for watching a specific location in a container context
> separated by the mount and the network namespaces. We have multiple mount
> points at the same place (eg. the mount point inheritance, the container
> configuration and the init scripts may mount /dev or /var/run several time)
> and the network namespace separation will make impossible to watch udev
> event via a netlink socket. I didn't look at the inotify implementation but
> IMHO, it should be worth to add IN_MOUNT and IN_UNMOUNT events for inotify
> no ?

These events wouldn't work, and they are long removed from the kernel
and don't exist.

You need to poll() /proc/mounts, and any changes in it will wake you
up with POLL_ERR. /proc/mounts should be namespace aware.

Kay
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