tmpfs experimental?

[Wojciech Puchar]

> multiple times:
>
>  ianto# mount | grep ' /tmp'
>  tmpfs on /tmp (tmpfs, local)
>  ianto# mount /tmp
>  ianto# mount | grep ' /tmp'
>  tmpfs on /tmp (tmpfs, local)
>  tmpfs on /tmp (tmpfs, local)
>  ianto# umount /tmp
>  ianto# mount | grep ' /tmp'
>  tmpfs on /tmp (tmpfs, local)
>  ianto#

it's not only tmpfs. you may mount ufs readonly, or nfs multiple times on 
the same place.

It's not tmpfs specific problem IMHO. There is no checking in mount for 
that case.