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

[Neal H. Walfield]

At Fri, 12 Jul 2013 15:07:59 +0200,
Justus Winter wrote:
> Quoting Samuel Thibault (2013-07-12 14:44:31)
> > Neal H. Walfield, le Fri 12 Jul 2013 13:52:17 +0200, a écrit :
> > > I apologize if you've already explained this someplace else.
> > > 
> > > If I understand correctly, you want to get all the nodes with active
> > > and passive translators.  This potentially requires scanning every
> > > inode on an ext3 file system.  This could take a very long time.  Is
> > > that really the intention?
> 
> That's an interesting point. Btw, settrans --recursive is currently
> implemented like this, I'll patch this also to use the translator
> list.

--recursive only applies to the active translators, not the passive
translators.  Also, it doesn't need to shutdown shortcut translators,
such as, symlinks, which should perhaps be returned by your proposed
RPC.

> > No, just the active ones.
> 
> Actually the code also tracks passive translators being set, but of
> course we don't know anything about any previously set passive
> translators.

I don't like this behavior.

> Richard and me agreed that for most purposes one needs an
> mtab file for (e.g. fsck) it is also interesting to know whether a
> passive translator is set and what device it would use because any
> user could trigger the translator start at any time.

I don't think this justifies the ugliness.


I don't like your solution to the mtab problem.  But, as you admit,
it's really a solution to the fsck problem.  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.  On boot, the mtab translator is started and calls each
call back.  It's not perfect, but it's a lot less ugly.

Neal