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Date: Thu, 16 Aug 2012 16:05:42 +0100
From: Al Viro <viro@ZenIV.linux.org.uk>
To: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: "J. Bruce Fields" <bfields@fieldses.org>, linux-kernel@vger.kernel.org,
        linux-fsdevel@vger.kernel.org, Alexey Dobriyan <adobriyan@gmail.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Pavel Emelyanov <xemul@parallels.com>,
        James Bottomley <jbottomley@parallels.com>,
        Matthew Helsley <matt.helsley@gmail.com>
Subject: Re: [patch 4/8] fs, exportfs: Add export_encode_inode_fh helper
Message-ID: <20120816150542.GV23464@ZenIV.linux.org.uk>
References: <20120815092116.700948346@openvz.org>
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On Thu, Aug 16, 2012 at 06:57:00PM +0400, Cyrill Gorcunov wrote:

> Guys, would the patch below be more-less acceptible?
> In inotify I think we could pass "parent" as NULL and use general
> encode engine then (ie it will look like someone called for
> name_to_handle_at on inotify target).

Wait.  What the hell are you going to do with those afterwards?
Again, there's a shitload of filesystems that cannot be exported
over NFS, exactly because there's no way to implement sanely
working fhandles.  And idiotify is allowed for all of them.

You *can't* decode anything fhandle-like on e.g. sysfs.  Or procfs.
Or configfs.  Or any network filesystem (I'd argue that we should simply
ban idiotify on those, but good luck doing that).  You *can* do that
for FAT derivatives, but only if you have parent directory when creating
that sucker.