[uml-devel] ubd option parsing problem when using cow filesystems in kernel 3.4

["David Fernández" <david@dit.upm.es>]

Hi,

It seems that the parsing of ubd option is broken in kernels 3.4.X when 
using COW filesystems. Let me show the tests I've done so far.

When starting a virtual machine using a cow fs without pathname:

   linux-3.4.1 udba=cow_fs,debian.img

it works, but the cow file created is named 'cow_fs,debian.img' instead 
of 'cow_fs'.

However, when specifying full pathnames for the cow and root filesystem:

   linux-3.4.1 udba=/pathto/cow_fs,/pathto/debian.img

you get a kernel panic and the following errors:

   Open of COW file '/root/uml/test/cow_fs,/root/uml/test/debian.img' 
failed, errno = 2
   Failed to open '/root/uml/test/cow_fs,/root/uml/test/debian.img', 
errno = 2
   ubda: Can't open "/root/uml/test/cow_fs,/root/uml/test/debian.img": 
errno = 2
   Open of COW file '/root/uml/test/cow_fs,/root/uml/test/debian.img' 
failed, errno = 2
   Failed to open '/root/uml/test/cow_fs,/root/uml/test/debian.img', 
errno = 2
   ubda: Can't open "/root/uml/test/cow_fs,/root/uml/test/debian.img": 
errno = 2
   VFS: Cannot open root device "98:0" or unknown-block(98,0): error -2
   Please append a correct "root=" boot option; here are the available 
partitions:
   6200         2097152 ubda  driver: uml-blkdev
   Kernel panic - not syncing: VFS: Unable to mount root fs on 
unknown-block(98,0)

The same tests work perfectly with kernel 3.3.8 and older versions. To 
test I've used a debian 6.0 rootfs.

Any idea of the cause of the problem? A simple 'diff' between 3.3 and 
3.4 versions shows the option parsing code has changed significantly.

Best regards,
David Fernández
Virtual Networks over linuX (VNX)
http://vnx.dit.upm.es

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