Re: [PATCH 1/6] Add a dentry op to handle automounting rather than abusing follow_link() [ver #2]

From: David Howells <dhowells@redhat.com>
To: Ian Kent <raven@themaw.net>
Cc: dhowells@redhat.com, viro@ZenIV.linux.org.uk,
	linux-fsdevel@vger.kernel.org, linux-afs@lists.infradead.org,
	linux-nfs@vger.kernel.org, linux-cifs@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/6] Add a dentry op to handle automounting rather than abusing follow_link() [ver #2]
Date: Tue, 27 Jul 2010 09:48:41 +0100	[thread overview]
Message-ID: <12883.1280220521@redhat.com> (raw)
In-Reply-To: <1280202225.2944.20.camel@localhost>

Ian Kent <raven@themaw.net> wrote:

> Is this something others need?

Not as far as I know...  I think autofs is the only one doing out-of-kernel
automounting.

That doesn't mean it shouldn't be provided, though...

> Again, the exists vs not yet exists case for paths within indirect
> autofs mounts. At the moment I can just set the flag on all dentrys in
> the autofs fs and return EXDEV for non-empty directories in order to
> return the dentry as a path component. OTOH if the dentry is a mount
> embeded in the path and the mount fails we get a error return.

Seems redundant, but I'd say go with it for now.  Maybe we can offload
S_AUTOMOUNT to the dentry.

> I could clear the flag on non-root parent dentrys during mkdir if this
> is needed by others.

I'm not sure that would actually matter, since it would come to
follow_automount() at the same place.

Note that someone who tries to stat() with AT_NO_AUTOMOUNT will cause the call
to d_automount() to be suppressed and will see the negative or non-mounted
directory.  That might be okay for you.

David