linux-kernel - Re: [PATCH 0/2] Fix hardlinks in overlay

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Date:	Mon, 7 Mar 2016 11:49:31 +0100
From:	Miklos Szeredi <miklos@...redi.hu>
To:	Alexander Morozov <alexandr.morozov@...ker.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Alexander Morozov <lk4d4@...ker.com>,
	"linux-unionfs@...r.kernel.org" <linux-unionfs@...r.kernel.org>
Subject: Re: [PATCH 0/2] Fix hardlinks in overlay

On Fri, Oct 9, 2015 at 9:34 PM, Alexander Morozov
<alexandr.morozov@...ker.com> wrote:
> There were reports that overlay doesn't work very well with unix-sockets.
> In particular you can't access unix-socket through hardlink on overlay fs.
> Problem is that overlay creates different inodes for hardlinks and code in
> net/unix/af_unix.c relies on inodes for unix-socket lookup. I think this
> affects any code which relies on inodes from kern_path. There is helper
> d_backing_inode, which I think supposed to get inodes from underlying fs
> (for example ext4), but in current implementation it does nothing.  These
> patches made on top of v4.3-rc4 of main linux tree (master is broken for my
> ubuntu VM), but I tested that they applying on master and there was no
> changes to overlay since v4.3-rc4.
>
> Alexander Morozov (2):
>   fs/overlay: move update and instantiate dentry code to function
>   fs/overlay: use same inodes for hardlinks

Problem is with lookup: how do we go from backing dentry to overlayfs
dentry so the inode can be shared?

Thanks,
Miklos