overlayfs: missing upperdir or lowerdir or workdir Unable to mount directory

[xiangzhai]

Hi Matthias,

I built the 3.18 for my ArchLinux box

Linux archlinux 3.18.0-rc4 #2 SMP Wed Nov 12 15:03:39 CST 2014 x86_64 GNU/Linux

There are installed in Limba /opt/software

$ lipa list
[libfoo-1.0] Limba Foo Library 1.0
[foobar-1.0] Limba FooBar 1.0

Then I tried to runapp foobar-1.0:

1. cd limba/build/tools/runapp
2. sudo ./runapp foobar-1.0:

It thrown overlayfs's error

overlayfs: missing upperdir or lowerdir or workdir Unable to mount directory

So I just monkey patch the https://github.com/ximion/limba/blob/master/tools/runapp/runapp.c

-       tmp = g_strdup_printf ("lowerdir=%s,upperdir=%s", LI_SW_ROOT_PREFIX, main_data_path);
+       tmp = g_strdup_printf ("lowerdir=%s,upperdir=%s,workdir=/root", LI_SW_ROOT_PREFIX, main_data_path);

I am not familiar with overlayfs right now, and I will read Kernel's Document about it, but perhaps someone please give me some advice, thanks a lot!

Regards,
Leslie Zhai

[ximion]

I don't want to jump to conclusions too fast, but this might be a kernel bug...
The code there says:

    if (!ufs->config.upperdir || !ufs->config.lowerdir ||
        !ufs->config.workdir) {
            pr_err("overlayfs: missing upperdir or lowerdir or workdir\n");

And an upper and lowerdir are given... (I am also looking at https://lkml.org/lkml/2014/11/10/129 right now)
One question: Does /opt/swroot exist? (did you run sudo make install?)
Also, the command to run FooBar should be something like:

runapp foobar-1.0:/bin/foo

(if installed, the binary is suid-root and drops privileges as soon as possible - so no need for an explicit sudo)
If instlled using sudo lipa install, you should also have a link to it in your desktops application menu ;-)

[xiangzhai]

Hi @ximion

Sorry for my late reply, I have to look after my wife she is pregnant ;)

Does /opt/swroot exist?

Yes, it exist!

tree -d /opt/
/opt/
├── software
│   ├── foobar-1.0
│   │   └── data
│   │       ├── bin
│   │       ├── etc
│   │       ├── lib
│   │       └── share
│   │           ├── applications
│   │           ├── info
│   │           └── man
│   │               └── man1
│   └── libfoo-1.0
│       └── data
│           └── lib
└── swroot

Also, the command to run FooBar should be something like: runapp foobar-1.0:/bin/foo

I am sorry I have bad habit: I often prefer to run lipa, lipkgen and runapp under ./build/tools/subdirectory directly ;P Because I failed to lipkgen build so I simply added some DEBUG info to li-installer.c, li-package.c, etc. And you helped me to figure it out ;) http://blog.tenstral.net/2014/11/introducing-limba-a-software-installer-experiment.html

And an upper and lowerdir are given... (I am also looking at https://lkml.org/lkml/2014/11/10/129 right now)

_the patch is for the kernel`s git_ it might be not suitable for 3.18.0-rc4

emm, I am reading the linux-3.18-rc4/Documentation/filesystems/overlayfs.txt
in the Directories section, it suggests mount like that:

mount -t overlayfs overlayfs -olowerdir=/lower,upperdir=/upper,\                 
workdir=/work /merged

So I simply added workdir=/root, it is a MONKEY patch ;P

diff --git a/tools/runapp/runapp.c b/tools/runapp/runapp.c                         
index 8a70b41..6261c90 100644                                                      
--- a/tools/runapp/runapp.c                                                        
+++ b/tools/runapp/runapp.c                                                        
@@ -146,7 +146,8 @@ mount_overlay (const gchar *pkgid)                             
            goto out;                                                              
        }                                                                          
    }                                                                              
-   tmp = g_strdup_printf ("lowerdir=%s,upperdir=%s", LI_SW_ROOT_PREFIX, main_data_path);
+   tmp = g_strdup_printf ("lowerdir=%s,upperdir=%s,workdir=/root", LI_SW_ROOT_PREFIX, main_data_path);
+   printf("DEBUG: %s %s, %d %s\n", __FILE__, __func__, __LINE__, tmp);         
    res = mount ("", LI_SW_ROOT_PREFIX,                                            
                 "overlayfs", MS_MGC_VAL | MS_RDONLY | MS_NOSUID, tmp);            
    g_free (tmp);

Finally it worked ;)

runapp foobar-1.0:/bin/foo
DEBUG: /home/project/xiangzhai/limba/tools/runapp/runapp.c mount_overlay, 150 lowerdir=/opt/swroot,upperdir=/opt/software/foobar-1.0/data,workdir=/root
foobar version 1.0.0
Hello World from libfoo!

'Configuration' file /opt/swroot/etc/foo-config:
Bla bla bla.

Press ENTER to exit this program.

But I need to be familiar with overlayfs by reading the doc and source code, thanks for your reply ;)

Regards,
Leslie Zhai

[ximion]

Looks like workdir is sometimes needed and sometimes not - I still need to figure oit how to reproduce this issue, but in any case, adding a workdir for compatibility seems to be an appropriate fix...
And yes, the kernel patch is for the next release (but it's something I am looking forward to).
To increase verbosity, the --verbose flag or the environment variable G_MESSAGES_DEBUG=all could be useful.

I'll come up with a fix which includes a workdir soon.

[ximion]

Can you please pull Git master, recompile Limba again (ensure that it picks up the right headers accompanying your 3.18 kernel), and see if this issue is fixed?
I tried this on a Fedora and Debian machine, using the 3.18 kernel and a 3.16 kernel with the OverlayFS module loaded, and it seems to work.
(Although checking the kernel version at runtime would be more flexible - that's something to do in future, or drop support for pre-3.18 kernels entirely)

[xiangzhai]

Hi @ximion

This issue fixed ;)

I tried this on a ArchLinux box, using the 3.18.0-rc kernel with the _overlayfs_ built-in

Thanks for your great job ;)

Regards,
Leslie Zhai