From: ebiederm@xmission.com (Eric W. Biederman)
To: Ian Kent <raven@themaw.net>
Cc: Mateusz Guzik <mguzik@redhat.com>, NeilBrown <neilb@suse.com>,
Andrew Morton <akpm@linux-foundation.org>,
autofs mailing list <autofs@vger.kernel.org>,
Kernel Mailing List <linux-kernel@vger.kernel.org>,
Al Viro <viro@ZenIV.linux.org.uk>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
Omar Sandoval <osandov@osandov.com>
Subject: Re: [PATCH 3/4] autofs - make mountpoint checks namespace aware
Date: Tue, 27 Sep 2016 08:14:27 -0500 [thread overview]
Message-ID: <871t057ado.fsf@x220.int.ebiederm.org> (raw)
In-Reply-To: <1474941132.3390.6.camel@themaw.net> (Ian Kent's message of "Tue, 27 Sep 2016 09:52:12 +0800")
Ian Kent <raven@themaw.net> writes:
> On Mon, 2016-09-26 at 11:05 -0500, Eric W. Biederman wrote:
>> Ian Kent <raven@themaw.net> writes:
>>
>> > On Fri, 2016-09-23 at 14:15 -0500, Eric W. Biederman wrote:
>> > > Ian Kent <raven@themaw.net> writes:
>> > >
>> > > 2> On Thu, 2016-09-22 at 20:37 -0500, Eric W. Biederman wrote:
>> > > > > Ian Kent <raven@themaw.net> writes:
>> > > > >
>> > > > > > On Thu, 2016-09-22 at 10:43 -0500, Eric W. Biederman wrote:
>> > > > > > > Ian Kent <raven@themaw.net> writes:
>> > > > > > >
>> > > > > > > > Eric, Mateusz, I appreciate your spending time on this and
>> > > > > > > > particularly
>> > > > > > > > pointing
>> > > > > > > > out my embarrassingly stupid is_local_mountpoint() usage
>> > > > > > > > mistake.
>> > > > > > > >
>> > > > > > > > Please accept my apology for the inconvenience.
>> > > > > > > >
>> > > > > > > > If all goes well (in testing) I'll have follow up patches to
>> > > > > > > > correct
>> > > > > > > > this
>> > > > > > > > fairly
>> > > > > > > > soon.
>> > > > > > >
>> > > > > > > Related question. Do you happen to know how many mounts per mount
>> > > > > > > namespace tend to be used? It looks like it is going to be wise
>> > > > > > > to
>> > > > > > > put
>> > > > > > > a configurable limit on that number. And I would like the default
>> > > > > > > to
>> > > > > > > be
>> > > > > > > something high enough most people don't care. I believe autofs is
>> > > > > > > likely where people tend to use the most mounts.
>> > > >
>> > > > Yes, I agree, I did want to try and avoid changing the parameters to
>> > > > ->d_mamange() but passing a struct path pointer might be better in the
>> > > > long
>> > > > run
>> > > > anyway.
>> > >
>> > > Given that there is exactly one implementation of d_manage in the tree I
>> > > don't imagine it will be disruptive to change that.
>> >
>> > Yes, but it could be used by external modules.
>> >
>> > And there's also have_submounts().
>>
>> Good point about have_submounts.
>>
>> > I can update that using the existing d_walk() infrastructure or take it
>> > (mostly)
>> > into the autofs module and get rid of have_submounts().
>> >
>> > I'll go with the former to start with and see what people think.
>>
>> That will be interesting to so. It is not clear to me that if d_walk
>> needs to be updated, and if d_walk doesn't need to be updated I would
>> be surprised to see it take into autofs. But I am happy to look at the
>> end result and see what you come up with.
>
> I didn't mean d_walk() itself, just the have_submounts() function that's used
> only by autofs these days. That's all I'll be changing.
>
> To take this functionality into the autofs module shouldn't be a big deal as it
> amounts to a directory traversal with a check at each node.
>
> But I vaguely remember talk of wanting to get rid of have_submounts() and autofs
> being the only remaining user.
>
> So I mentioned it to try and elicit a comment, ;)
>From my perspective the key detail is that d_walk is private to dcache.c
That said you want to look at may_umount_tree, or may_umount that
are already exported from fs/namespace.c, and already used by autofs.
One of those may already do the job you are trying to do.
It looks like at least may_umount needs to be examined to see if it does
the right thing for the tweaked semantics of autofs.
Eric
next prev parent reply other threads:[~2016-09-27 13:28 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-09-14 6:14 [PATCH 1/4] fs - make is_local_mountpoint() usable by others Ian Kent
2016-09-14 6:14 ` [PATCH 2/4] fs - add have_local_submounts() Ian Kent
2016-09-14 6:14 ` [PATCH 3/4] autofs - make mountpoint checks namespace aware Ian Kent
2016-09-14 17:28 ` Eric W. Biederman
2016-09-15 0:09 ` Ian Kent
2016-09-15 0:32 ` Omar Sandoval
2016-09-15 2:08 ` Eric W. Biederman
2016-09-15 4:12 ` Ian Kent
2016-09-15 8:19 ` Ian Kent
2016-09-16 0:47 ` Eric W. Biederman
2016-09-16 2:58 ` Ian Kent
2016-09-19 0:58 ` Ian Kent
2016-09-20 16:09 ` Eric W. Biederman
2016-09-15 1:03 ` Ian Kent
2016-09-16 21:14 ` Omar Sandoval
2016-09-17 20:10 ` Mateusz Guzik
2016-09-19 1:36 ` Ian Kent
2016-09-20 16:50 ` Eric W. Biederman
2016-09-20 22:44 ` Ian Kent
2016-09-20 23:00 ` Ian Kent
2016-09-22 1:33 ` Ian Kent
2016-09-22 15:43 ` Eric W. Biederman
2016-09-23 0:55 ` Ian Kent
2016-09-23 1:37 ` Eric W. Biederman
2016-09-23 4:26 ` Ian Kent
2016-09-23 12:00 ` Ian Kent
2016-09-28 10:18 ` Ian Kent
2016-09-23 19:15 ` Eric W. Biederman
2016-09-24 0:11 ` Ian Kent
2016-09-26 16:05 ` Eric W. Biederman
2016-09-27 1:52 ` Ian Kent
2016-09-27 13:14 ` Eric W. Biederman [this message]
2016-09-28 0:19 ` Ian Kent
2016-09-14 6:14 ` [PATCH 4/4] fs - remove unused have_submounts() function Ian Kent
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