Re: [PATCH 10/17] hurd: add fsys_get_children

[Neal H. Walfield]

At Mon, 15 Jul 2013 10:37:37 +0200,
Samuel Thibault wrote:
> > I don't like your solution to the mtab problem.  But, as you admit,
> > it's really a solution to the fsck problem.
> 
> Not only. It's also about umount being able to know what to unmount when
> calling umount /dev/cdrom, about mount/df being able to have a list of
> mounted filesystems, etc. The fsck problem could be solved by simply
> having an exclusive lock on the underlying device node.

Then perhaps we need fsys_set_user / fsys_get_user RPCs.  When a
process begins to use a node, it can optionally register itself as a
user.  Then others can determine whether the node is being used and
who it is.  The user port would be an unauthenticated port
implementing, for instance, the fsys interface.

> > So, let's think about the
> > fsck problem.  What we need is a registry.  I propose an mtab
> > translator.  Translators register with it when they start and register
> > a call back.
> 
> Where do they register? Is this yet another well-known translator,
> outside of the filesystem? Having it distributed seems much more
> elegant.

/servers/mtab and $USER/server/mtab.

Neal