From: NeilBrown <neilb@suse.com>
To: Luis de Bethencourt <luisbg@osg.samsung.com>,
        linux-fsdevel@vger.kernel.org
Date: Sun, 06 Nov 2016 09:03:45 +1100
Cc: Richard Weinberger <richard@nod.at>, linux-nfs@vger.kernel.org
Subject: Re: When is export_operations.get_parent triggered?
In-Reply-To: <581DD7B0.8080906@osg.samsung.com>
References: <581DD7B0.8080906@osg.samsung.com>
Message-ID: <8760o1pose.fsf@notabene.neil.brown.name>
MIME-Version: 1.0
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Sender: linux-nfs-owner@vger.kernel.org

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On Sat, Nov 05 2016, Luis de Bethencourt wrote:

> Hi all,
>
> I recently played with adding the basics to make befs exportable via NFS [0].
>
> I want to implement the get_parent member of the export_operations struct as
> well, but I can't seem to trigger this member being called. I have implemented
> a solution which I feel is wrong [1], but want to be able to test it before
> moving forward.
>
> When is this member triggered? Any advice?

This is required when a filehandle for a directory arrives, but the
directory is not in the dcache.
NFSD needs to find dentries for the directory, the parent, the
grandparent etc all the way up to the root.

The simplest way to trigger this is to mount the filesystem onto a
different machine, 'cd' into a fairly deep directory, then reboot the
server (or unexport, unmount, remount, re-export).
Now 'ls -l' on the client.  That should trigger calls to ->get_parent.

->get_parent() is a log like performing a lookup of "..".

NeilBrown

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