Re: RFC: unionfs multiple mounts, cross mounts and recursive mounts limits and manegement feature

On Thu, 2011-04-21 at 14:49 +0900, Daichi GOTO wrote:

> It is adjustable with sysctl value 'vfs.unionfs.recursive_limit' as
> multiple mounts limits. The default value is 1 and it means two-layered ok.
> Max value of 'vfs.unionfs.recursive_limit' is 8, it is heuristic value. 
> I couldn't get a system panic unless 'vfs.unionfs.recursive_limit' is over 8.
> 

Hmm, 8 is not enough for me, i need more :)

On the other hand, why do we need recursion in unionfs_statfs
at all? IMHO recursion in kernel is evil because it has a potencial
of resource exhaustion.

This recursion in unionfs_statfs is used to gather statistic (some of
which is faked according to comments in the procedure)

why not replace recursion with cycle? (I'm not skilled enough do do
that :)



and a feature request:
it would be great if it was possible to umount one of multiple unionfs:

mount -t unionfs /var/ftpdata1 /var/ftp
mount -t unionfs /var/ftpdata2 /var/ftp

how to unmount /var/ftpdata1 only?