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

[Miklos Szeredi]

On Fri, Oct 9, 2015 at 9:34 PM, Alexander Morozov
<alexandr.morozov@xxxxxxxxxx> 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