Re: [PATCH 0/23] File descriptor hot-unplug support v2

[Miklos Szeredi]

On Mon, 8 Jun 2009, Al Viro wrote:
> On Mon, Jun 08, 2009 at 11:41:19AM +0200, Miklos Szeredi wrote:
> > On Sat, 6 Jun 2009, Al Viro wrote:
> > > Frankly, I very much suspect that force-umount is another case like that;
> > > we'll need a *lot* of interesting cooperation from fs for that to work and
> > > to be useful.  I'd be delighted to be proven incorrect on that one, so
> > > if you have anything serious in that direction, please share the details.
> > 
> > Umm, not sure why we'd need cooperation from the fs.  Simply wait for
> > the operation to exit the filesystem or driver.  If it's a blocking
> > operation, send a signal to interrupt it.
> 
> And making sure that operations *are* interruptible (and that we can cope
> with $BIGNUM new failure exits correctly) does not qualify as cooperation?

I'm still not getting what the problem is.  AFAICS file operations are
either

 a) non-interruptible but finish within a short time or
 b) may block indefinitely but are interruptible (or at least killable).

Anything else is already problematic, resulting in processes "stuck in
D state".

Can you give a more concrete example about your worries?

Thanks,
Miklos
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