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From: Vivek Goyal <vgoyal@redhat.com>
To: Amir Goldstein <amir73il@gmail.com>
Cc: Zhihao Cheng <chengzhihao1@huawei.com>,
	Miklos Szeredi <miklos@szeredi.hu>,
	overlayfs <linux-unionfs@vger.kernel.org>
Subject: Re: [QUESTION] Why overlayfs cannot mounted as nfs_export and metacopy?
Date: Mon, 9 Aug 2021 15:56:42 -0400	[thread overview]
Message-ID: <YRGIevRDg6hrdYQl@redhat.com> (raw)
In-Reply-To: <CAOQ4uxiO7zt7sywNqyd-WwCVds9-NqRAixham9yVeN7F+JhXoA@mail.gmail.com>

On Sat, Aug 07, 2021 at 02:05:15PM +0300, Amir Goldstein wrote:
> On Sat, Aug 7, 2021 at 1:17 PM Zhihao Cheng <chengzhihao1@huawei.com> wrote:
> >
> > Hi, all.
> >
> > As title said. I wonder to know the reason for overlayfs mount failure
> > with '-o nfs_export=on,metacopy=on'.
> >
> > I modified kernel to enable these two options 'on',  it looks like that
> > overlayfs can still work fine under nfs_v4.
> >
> > Besides, I can get no more information about the reason from source
> > code, maybe I missed something.
> >
> 
> It's because ovl_obtain_alias() (decoding a disconnected non-dir file handle)
> does not know how to construct a metacopy overlayfs inode.
> 
> Maybe Vivek will be able to point you to the discussion that lead to making
> the features mutually exclusive.

I think I had not implemented metacopy with nfs export because it seemed
non-trivial and I did not need nfs export feature support with metacopy.
So I decided to narrow down the problem space and not support nfs
export and metacopy together.

It will be good if somebody can dive deeper and make it work (if it
is possible to make it work).

Vivek
> 
> I don't remember any other reason.
> 
> Thanks,
> Amir.
> 


      parent reply	other threads:[~2021-08-09 19:56 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-07 10:17 [QUESTION] Why overlayfs cannot mounted as nfs_export and metacopy? Zhihao Cheng
2021-08-07 11:05 ` Amir Goldstein
2021-08-07 16:37   ` Amir Goldstein
2021-08-09  9:21     ` Zhihao Cheng
2021-08-09 21:35     ` Vivek Goyal
2021-08-10  4:17       ` Amir Goldstein
2021-08-10 19:48         ` Vivek Goyal
2021-08-10 20:00           ` Vivek Goyal
2021-08-11  6:51           ` Amir Goldstein
2021-08-16 18:27             ` Vivek Goyal
2021-08-16 18:44               ` Amir Goldstein
2021-08-16 19:00                 ` Vivek Goyal
2021-08-09 19:56   ` Vivek Goyal [this message]

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