[Unionfs] Unionfs 2.0 on 2.6.9 kernel

[Beyerle Urs]

Erez Zadok wrote:
> In message <46B8B8B8.6080308 at psi.ch>, Urs Beyerle writes:
>> Erez Zadok wrote:
> [...]
> 
>>> Urs, try this small fix.  This seems to fix a similar problem for someone
>>> else, but I've not yet released this small fix.  Let me know if it works for
>>> you.
> 
> [...]
> 
>> Hi Erez,
>>
>> great, works!
>> Now I can start using unionfs 2.0 on 2.6.9 RHEL kernel.
>>
>> Thanks
>>
>>       Urs
> 
> Wondeful.  I'll release and update to the 2.6.9 port soon.
> 
> Erez.

Hi, Erez,

# mount -t unionfs -o dirs=/dir1=rw:/dir2=ro none /mnt/unionfs
now works and I can work inside /mnt/unionfs.
I can also do

# mount -t unionfs -o dirs=/dir1=rw none /mnt/unionfs
# mount -t unionfs -o remount,ro none /mnt/unionfs

But I have a problem when adding a new branch:

# mount -t unionfs -o dirs=/dir1=rw none /mnt/unionfs
# mount -t unionfs -o remount,add=:/dir2:ro none /mnt/unionfs
mount: special device none does not exist

and in messages:
Aug  8 09:00:19 tux40 kernel: unionfs: error accessing lower directory "/dir2:ro" (error -2)

If I do
# mount -t unionfs -o remount,add=:/dir2 none /mnt/unionfs

I even get a kernel panic:

Aug  8 10:24:14 tux40 kernel: Unable to handle kernel NULL pointer dereference at virtual 
address 00000020
Aug  8 10:24:14 tux40 kernel:  printing eip:
Aug  8 10:24:14 tux40 kernel: f8ca1172
Aug  8 10:24:14 tux40 kernel: *pde = 00000000
Aug  8 10:24:14 tux40 kernel: Oops: 0000 [#1]
Aug  8 10:24:14 tux40 kernel: Modules linked in: unionfs(U) cisco_ipsec(U) libafs(U) md5 
ipv6 autofs4 i2c_dev i2c_core sunrpc
dm_mirror dm_mod button battery ac pcnet32 mii floppy ata_piix libata scsi_mod ext3 jbd
Aug  8 10:24:14 tux40 kernel: CPU:    0
Aug  8 10:24:14 tux40 kernel: EIP:    0060:[<f8ca1172>]    Tainted: PF     VLI
Aug  8 10:24:14 tux40 kernel: EFLAGS: 00010246   (2.6.9-55.0.2.EL)
Aug  8 10:24:14 tux40 kernel: EIP is at unionfs_remount_fs+0x529/0x73f [unionfs]
Aug  8 10:24:14 tux40 kernel: eax: f6367b40   ebx: 00000000   ecx: f56ea800   edx: 00000002
Aug  8 10:24:14 tux40 kernel: esi: 00000001   edi: f63673c0   ebp: 00000000   esp: f4c8be88
Aug  8 10:24:14 tux40 kernel: ds: 007b   es: 007b   ss: 0068
Aug  8 10:24:14 tux40 kernel: Process mount (pid: 3461, threadinfo=f4c8b000 task=f4c992e0)
Aug  8 10:24:14 tux40 kernel: Stack: 00000001 fffdb24b f4c8bea8 00000158 f56ea800 00000002 
f4cea000 c0194115
Aug  8 10:24:14 tux40 kernel:        00000000 00000000 f4cc2940 00000000 f6367da0 00000000 
00000000 00000001
Aug  8 10:24:14 tux40 kernel:        00000001 f4c8bef4 f56ea800 00000000 00000001 00000000 
f56ea864 f8cb0ba0
Aug  8 10:24:14 tux40 kernel: Call Trace:
Aug  8 10:24:14 tux40 kernel:  [<c0194115>] sync_inodes_sb+0xe9/0x15b
Aug  8 10:24:14 tux40 kernel:  [<c0173c3a>] do_remount_sb+0xaa/0xdb
Aug  8 10:24:14 tux40 kernel:  [<c018eec2>] do_remount+0x87/0xca
Aug  8 10:24:14 tux40 kernel:  [<c018fc87>] do_mount+0x126/0x190
Aug  8 10:24:14 tux40 kernel:  [<c014f754>] __alloc_pages+0xb4/0x2a6
Aug  8 10:24:14 tux40 kernel:  [<c019018e>] sys_mount+0x10d/0x1df
Aug  8 10:24:14 tux40 kernel:  [<c031af83>] syscall_call+0x7/0xb
Aug  8 10:24:14 tux40 kernel: Code: 24 24 89 4a 04 8b 43 3c 8b 54 24 3c 8b 40 64 89 50 34 
89 74 24 3c 8b 43 3c 8b 40 64 8b 70
28 3b 70 2c 7f 22 8b 40 3c 8b 5c f0 04 <8b> 43 20 e8 08 98 4e c7 8b 43 20 89 04 b7 8b 4c 
24 48 46 8b 41
Aug  8 10:24:14 tux40 kernel:  <0>Fatal exception: panic in 5 seconds