linux-kernel - Re: nfsd changes for 2.6.37

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Message-Id: <201010271723.59734.arnd@arndb.de>
Date:	Wed, 27 Oct 2010 17:23:59 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	Christoph Hellwig <hch@...radead.org>
Cc:	"J. Bruce Fields" <bfields@...ldses.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Bryan Schumaker <bjschuma@...app.com>,
	linux-nfs@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: nfsd changes for 2.6.37

On Wednesday 27 October 2010, Christoph Hellwig wrote:
> On Wed, Oct 27, 2010 at 10:55:39AM -0400, J. Bruce Fields wrote:
> > Hm, two problems:
> > 	- We introduce the possibility of fcntl(fd, F_SETLEASE, F_UNLCK)
> > 	  failing with ENOMEM.
> 
> splitt ->setlease into ->add_least and ->delete_lease.  No need to pass
> in a structure for the later.  No need to return one either.

That sounds like a good way to get rid of a lot of special cases, too.

> > 	- fasync_helper(.,.,1,.) sleeps.  Argh.
> 
> That's not new..

It comes back to the original problem with Bruce's patch though:
fcntl_setlease wants to atomically add a lease or fail. If
fasync_helper fails, we want to remove the lease that was
just added before anyone can see it. At the very least we need
to keep the flock from getting freed in another thread while
we call fasync_helper without the lock.

locks_delete_lock is also called with lock_flocks held and calls
fasync_helper...

	Arnd
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