From mboxrd@z Thu Jan  1 00:00:00 1970
From: Miklos Szeredi <miklos@szeredi.hu>
Subject: Re: [PATCH] [REPOST] fuse: drop dentry on failed revalidate
Date: Fri, 2 Aug 2013 16:42:00 +0200
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Cc: Ric Wheeler <rwheeler@redhat.com>, Anand Avati <avati@redhat.com>,
	Brian Foster <bfoster@redhat.com>,
	Linux FS Devel <linux-fsdevel@vger.kernel.org>,
	fuse-devel <fuse-devel@lists.sourceforge.net>,
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	David Howells <dhowells@redhat.com>,
	Eric Paris <eparis@redhat.com>
To: Jeff Layton <jlayton@redhat.com>
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On Fri, Aug 2, 2013 at 2:17 PM, Jeff Layton <jlayton@redhat.com> wrote:
> On Tue, 30 Jul 2013 18:16:55 +0200 Miklos Szeredi <miklos@szeredi.hu> wrote:

>> The other problem is that, unlike NFS, fuse doesn't currently
>> reconnect these subtrees when it finds them at a different point in
>> the tree.  d_drop on it just makes things worse because at that point
>> that subtree will not be accessible anymore (while the fuse fs is
>> mounted, that is).  This could be fixed pretty easily by using the
>> d_materialise_*() helpers.
>>
>
> Yes, but...
>
> This works on NFS since we have an expectation that we can identify an
> inode again when we see it. Given some of the strange userland
> filesystems that FUSE supports, does that expectation hold there? If
> not then you might still end up with disconnected subtrees.

We'll end up with disconnected subtrees in NFS as well.  That state
can remain indefinitely. It will either be reconnected when we come
accross the inode "by chance" or dissolved when it is no longer
referenced and the dentries reclaimed.

And as long as there are no mounts under the disconnected subtree,
there's no big problem.

If some strange filesystem doesn't support identifying a disconnected
subtree it will just not be reconnected.  But that can happen with NFS
as well, if the new location is never accessed, so it's not something
new.

Thanks,
Miklos