Hi again,
I've just fixed the issue here. The cause was that the inode passed to
unionfs_lower_inode() was no longer valid, so it had nothing to do
with UnionFS code itself. Thanks for your attention anyways.
Lucas
On 3/10/08, Lucas C. Villa Real <[EMAIL PROTECTED]> wrote:
> Hi Erez,
>
> I've just tested this with UnionFS 2.2.4 in 2.6.24.3, and the problem
> still persists. Do you have any pointers on this question?
>
> Thanks,
>
> Lucas
>
>
>
> ---------- Forwarded message ----------
> From: Lucas C. Villa Real <[EMAIL PROTECTED]>
> Date: Fri, Feb 22, 2008 at 12:53 AM
> Subject: unionfs_lower_dentry returns NULL
> To: [EMAIL PROTECTED]
>
>
> Hello guys,
>
> I'm debugging a problem that appeared after an upgrade from UnionFS
> 2.1.9 applied in a Linux 2.6.23.8 kernel to UnionFS 2.2.3 in a 2.6.24
> one. We at GoboLinux have a complement to the kernel named GoboHide,
> which allows one to hide dentries from userspace applications. The
> interface basically works through ioctls, where the dentry's inode
> number and the superblock which describes the mount point from a given
> path are stored in a list, which is later consulted at filldir, rmdir
> and unlink operations in the VFS. The inode number is taken right from
> userspace based on the information stored in the st_ino member in
> struct stat.
>
> Normal filesystems (ext2, reiserfs, jffs2, etc) doesn't require any
> special treatment: the inode numbers got from fstat() will match with
> the ones stored in their struct inode, and the comparison with the
> numbers stored in the gobohide list are straight forward. UnionFS,
> however, seems to store that in a different way -- the numbers read in
> fstat().st_ino are actually found in the UnionFS lower_dentry array.
>
> So far, the following code was being used to translate an inode number
> in GoboHide:
>
> ino_t gobolinux_translate_inode_nr(struct inode *inode)
> {
> ino_t ino = inode->i_ino;
> #ifdef CONFIG_UNION_FS
> if (inode->i_sb->s_op == &unionfs_sops) {
> /* we must take the inode number from the underlying filesystem */
> struct inode *lower_inode = unionfs_lower_inode(inode);
> ino = lower_inode->i_ino;
> }
> #endif
> return ino;
> }
>
> Since the switch to UnionFS 2.2.3, however, unionfs_lower_inode()
> returns NULL in some situations (vfs_rmdir). Since I'm not closed to
> UnionFS development, I'm not sure if this NULL pointer is coming from
> a bug or from a feature, so I'd really appreciate any pointers or
> suggestions in how to better handle with this situation.
>
> I'm attaching the GoboHide patch, just in case you want to test and
> reproduce the bug there. You'll also need a small userspace tool which
> can be downloaded from here:
> http://gobolinux.org/download/gobohide/GoboHide-0.13.tar.bz2
>
> The steps to reproduce are pretty simple:
> $ mount -t unionfs -o dirs=/some/dir=rw:/another/dir=ro none /mnt/unionfs
> $ cd /mnt/unionfs
> $ cp -a /path/to/some_directory .
> $ gobohide -h some_directory
> $ gobohide -l
> $ rm -rf some_directory
>
> At this point you should get an oops coming from the unexpected NULL
> pointer received from unionfs_lower_dentry (tested with a populated
> directory, but this shouldn't make a difference). The expected
> behavior would be to have some_directory removed from the filesystem
> tree and from the gobohide list (gobohide -l should not list it
> afterwards).
>
> Many thanks in advance, and once again thanks for your work on UnionFS!
>
> --
> Lucas
> powered by /dev/dsp
>
>
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