Re: Making forced unmounts work

[christos%astron.com@localhost (Christos Zoulas)]

In article <31490263-5A8E-411A-BB57-F7FC5CFFC733%eis.cs.tu-bs.de@localhost>,
J. Hannken-Illjes <hannken%eis.cs.tu-bs.de@localhost> wrote:
>The more I think the more I just want to remove forced unmounts.

I think that any operation that cannot be undone (and requires reboot
to be undone) makes the OS less resilient to failure.

>To take some examples:
>
>- A hard,nointr NFS mount hanging because the server stops responding.
>
>Even if it were possible to use fstrans_ here (and it would become ugly)
>it would not help.  The root node of the mount will likely be locked by the
>first thread trying to lookup so unmount won't be able to even lookup
>the mount point.  If it were possible to run `mount -u' or `unmount' it
>should be possible to update the mount as `soft,intr' and proceed as usual,
>kill threads blocking an unmount and unmount.

Store the normalized mount path with the mountpoint, look it up in the mount
list, make all blocked threads give an I/O error on the current operation,
etc.

christos