Re: 64-bit inode number issues

[Christoph Hellwig <hch@infradead.org>]

On Wed, Oct 04, 2006 at 03:18:21PM +0100, David Howells wrote:
> > 	Unfortunately there's a lot of broken userspace that can't deal
> > 	with 64bit inode numbers, so you need to make the lod behaviour
> > 	a mount option at least, probably even the default.  Given that
> > 	we're going to run into problems like that it might make sense
> > 	to make the option VFS-level instead of just in nfs.  (Note:
> > 	XFS already has an option like that)
> 
> This problem doesn't just apply to NFS.  It applies to any filesystem that can
> generate 64-bit inode numbers - which includes Ext3, I believe - so not
> applying the NFS patch doesn't really solve your problem (Al Viro asked me for
> examples of that, btw) and leaves my problem unsolved.

As you mention in your next mail ext3 is not affected.  XFS for example
is, that's why it has a 32bit inode numbers only mount option already.

> I think any solution has to apply at the VFS level or higher.  I'm not sure Al
> agrees though.  I think we have to do one of the following:
> 
>  (1) Turn on inode number compression (which tries to hide the problem).
> 
>  (2) Give an error to stat and getdents if the inode number can't be
>      represented by 32-bits.
> 
> And I think we're going to do this, that we need to do this on a per-superblock
> basis or on a per-system basis, and I think it should be _off_ by default.  It
> might also be possible to do it on a per-process level, but I suspect that'd be
> too much effort.

This definitly should be on a per-superblock basis, aka the mount option
I suggested above.    I don't think an actual scheme to deal with the
inode numbers at the VFS level makes sense, what I meant was only to do
a vfs-level mount option (numerical) instead of a per-filesystem one.

Al commented he doesn't like that.  He also think we should give the
64bit inode numbers a try, so I'd say:

 o add an inode32 option for nfs that mirrors the XFS option
 o turn it off by default in -mm and see what goes boom