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From:   Miklos Szeredi <miklos@szeredi.hu>
Date:   Thu, 2 Sep 2021 09:53:47 +0200
Message-ID: <CAJfpegu7rwoFXdtLusyRhrtFgMPxRShesxnBT2Q6iiC_iSGsfg@mail.gmail.com>
Subject: Re: [PATCH v2] BTRFS/NFSD: provide more unique inode number for btrfs export
To:     Christoph Hellwig <hch@infradead.org>
Cc:     NeilBrown <neilb@suse.de>,
        "J. Bruce Fields" <bfields@fieldses.org>,
        Chuck Lever <chuck.lever@oracle.com>,
        Linux NFS list <linux-nfs@vger.kernel.org>,
        Josef Bacik <josef@toxicpanda.com>,
        linux-fsdevel@vger.kernel.org
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On Thu, 2 Sept 2021 at 09:18, Christoph Hellwig <hch@infradead.org> wrote:

> >  Your attitude seems to be that this is a btrfs problem and must be
> >  fixed in btrfs.
>
> Yes.

st_ino space issues affect overlayfs as well.   The two problems are
not the same, but do share some characteristics.  And this limitation
will likely come up again in the future.

I suspect the long term solution would involve introducing new
userspace API (variable length inode numbers) and deprecating st_ino.
E.g. make stat return an error if the inode number doesn't fit into
st_ino and add a statx extension to return the full number.  But this
would be a long process...

Thanks,
Miklos