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From:   Miklos Szeredi <miklos@szeredi.hu>
Date:   Thu, 27 Feb 2020 10:36:38 +0100
Message-ID: <CAJfpegtRoXnPm5_sMYPL2L6FCZU52Tn8wk7NcW-dm4_2x=dD3Q@mail.gmail.com>
Subject: Re: [PATCH 00/17] VFS: Filesystem information and notifications [ver #17]
To:     Ian Kent <raven@themaw.net>
Cc:     Miklos Szeredi <mszeredi@redhat.com>,
        James Bottomley <James.Bottomley@hansenpartnership.com>,
        Steven Whitehouse <swhiteho@redhat.com>,
        David Howells <dhowells@redhat.com>,
        viro <viro@zeniv.linux.org.uk>,
        Christian Brauner <christian@brauner.io>,
        Jann Horn <jannh@google.com>,
        "Darrick J. Wong" <darrick.wong@oracle.com>,
        Linux API <linux-api@vger.kernel.org>,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>,
        lkml <linux-kernel@vger.kernel.org>
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On Thu, Feb 27, 2020 at 6:06 AM Ian Kent <raven@themaw.net> wrote:

> At the least the question of "do we need a highly efficient way
> to query the superblock parameters all at once" needs to be
> extended to include mount table enumeration as well as getting
> the info.
>
> But this is just me thinking about mount table handling and the
> quite significant problem we now have with user space scanning
> the proc mount tables to get this information.

Right.

So the problem is that currently autofs needs to rescan the proc mount
table on every change.   The solution to that is to

 - add a notification mechanism
 - and a way to selectively query mount/superblock information

right?

For the notification we have uevents in sysfs, which also supplies the
changed parameters.  Taking aside namespace issues and addressing
mounts would this work for autofs?

Thanks,
Miklos