linux-kernel - Re: [PATCH 3/7] vfs: Add a mount-notification facility

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Message-ID: <30028.1559084917@warthog.procyon.org.uk>
Date:   Wed, 29 May 2019 00:08:37 +0100
From:   David Howells <dhowells@...hat.com>
To:     Jann Horn <jannh@...gle.com>
Cc:     dhowells@...hat.com, Al Viro <viro@...iv.linux.org.uk>,
        raven@...maw.net, linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        Linux API <linux-api@...r.kernel.org>,
        linux-block@...r.kernel.org, keyrings@...r.kernel.org,
        linux-security-module <linux-security-module@...r.kernel.org>,
        kernel list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/7] vfs: Add a mount-notification facility

David Howells <dhowells@...hat.com> wrote:

> > It might make sense to redesign this stuff so that watches don't hold
> > references on the object being watched.
>
> I explicitly made it hold a reference so that if you place a watch on an
> automounted mount it stops it from expiring.
> 
> Further, if I create a watch on something, *should* it be unmountable, just as
> if I had a file open there or had chdir'd into there?

It gets trickier than that as I need a ref on the dentry on which the watch is
rooted to prevent it from getting culled.

David