Re: [PATCH] lockd: unlock when client rejects GRANTED_MSG

[Frank van Maarseveen <frankvm@frankvm.com>]

On Tue, Jul 03, 2007 at 04:53:02PM -0400, J. Bruce Fields wrote:
> On Sun, Jul 01, 2007 at 05:11:54PM +0200, Frank van Maarseveen wrote:
> > On Sun, Jul 01, 2007 at 10:58:32AM -0400, J. Bruce Fields wrote:
> > > On Sun, Jul 01, 2007 at 04:38:01PM +0200, Frank van Maarseveen wrote:
> > > > 
> > > > When lockd grants a blocked lock request after a while then the client
> > > > response on it should not be ignored: When the client rejects GRANTED_MSG
> > > > with GRANTED_RES NLM_LCK_DENIED then lockd on the server must release
> > > > the POSIX lock.
> > > 
> > > There's not really any way to "remove" a posix lock.  All you can do is
> > > issue an unlock, which isn't quite the same--for example, consider the
> > > case when the granted lock was a read lock downgrading a previously
> > > write-locked region.  Or perhaps it was locking a region only some of
> > > whose bytes where previously locked.
> > > 
> > > I have some bit-rotting patches that define a new "provisional" lock
> > > type that is like a posix lock except that it isn't combined with other
> > > existing locks--such a lock has the advantage that it really can be
> > > completely undone.  You can then break up the lock-applying process into
> > > two steps:
> > > 
> > > 	1. first apply a "provisional" lock (marked with an FL_BLOCK
> > > 	   lock type in my code), then
> > > 	2. when whoever originally requested the lock requests it,
> > > 	   convert the provisional lock until a real posix lock,
> > > 	   combining it with other locks as necessary.
> > > 
> > > So we could handle your case by delaying step number 2 until we get an
> > > affirmative response to the grant.
> > 
> > The affirmative response will never happen
> 
> The point of that scheme is that we can also handle a negative response,
> since the provisional lock is (unlike a regular posix lock) something
> that can be cancelled.
> 
> But I don't know how useful that really is in this case.

I think your patch is addressing something different. It _might_ fix
the nlm_grant_reply() bug as a side effect but that's already done by
the small patch I posted earlier so... I think it is best to consider
these issues separately.

But I'm still unsure about who's picking up NLM patches and if server
or client side matters.


-- 
Frank

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