Re: ext3 and like, mount point in module

[ebiederm@xmission.com (Eric W. Biederman)]

Tomas Bortoli <tomasbortoli@hotmail.it> writes:

>> What about chroot/namespaces/etc? :)
>
> I think chroot would work even so. Why would a program call chroot("..") on the root dir of the root fs? 
> It's unnecessary and tricky. A local program has all the information to know relative paths and move consequently.
> Anyway it is possible.
>
>
>> I'm not sure if it is worth the hassle, I bet some applications depend on that behavior.
>> But you can give it a try, I'd insert a negative dentry for ".." if ".." is child of the current
>> root.
>
> If with negative dentry you mean not putting ".." I've understood. 
> But, ".." is needed for file system mounted not on the root point, otherwise they would be disconnected from the "parent" fs.
> So, the "mount_point" variable is needed and it is not present in the file system module itself, as you said. 
> Where can I find the vfs module? 
> And, If I've understood what Al Viro said, it's correct to work on vfs rather than on the specific file system module.

fs/namei.c  follow_dotdot and follow_dotdot_rcu

You might also take a gander at the patches I have recently posted that
address a similiar but different issue with .. and bind mounts.  That
should at least show you where the code is.

Eric