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Date:   Fri, 30 Jul 2021 00:31:12 +0000
From:   Al Viro <viro@zeniv.linux.org.uk>
To:     NeilBrown <neilb@suse.de>
Cc:     Christoph Hellwig <hch@infradead.org>,
        Josef Bacik <josef@toxicpanda.com>,
        "J. Bruce Fields" <bfields@fieldses.org>,
        Chuck Lever <chuck.lever@oracle.com>, Chris Mason <clm@fb.com>,
        David Sterba <dsterba@suse.com>, linux-fsdevel@vger.kernel.org,
        linux-nfs@vger.kernel.org, linux-btrfs@vger.kernel.org
Subject: Re: [PATCH 04/11] VFS: export lookup_mnt()
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 <162742546551.32498.5847026750506620683.stgit@noble.brown>
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On Wed, Jul 28, 2021 at 08:37:45AM +1000, NeilBrown wrote:
> In order to support filehandle lookup in filesystems with internal
> mounts (multiple subvols in the one filesystem) reconnect_path() in
> exportfs will need to find out if a given dentry is already mounted.
> This can be done with the function lookup_mnt(), so export that to make
> it available.

IMO having exportfs modular is wrong - note that fs/fhandle.c is
	* calling functions in exportfs
	* non-modular
	* ... and not going to be modular, no matter what - there
are syscalls in it.