linux-kernel - Re: [PATCH] AFS: Implement file locking

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Message-ID: <7436.1180223730@redhat.com>
Date:	Sun, 27 May 2007 00:55:30 +0100
From:	David Howells <dhowells@...hat.com>
To:	"J. Bruce Fields" <bfields@...ldses.org>
Cc:	akpm@...l.org, linux-kernel@...r.kernel.org,
	linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH] AFS: Implement file locking

J. Bruce Fields <bfields@...ldses.org> wrote:

> > +	if (!afs_lock_manager) {
> > +		afs_lock_manager = create_singlethread_workqueue("kafs_lockd");
> > +		if (!afs_lock_manager)
> > +			return -ENOMEM;
> > +	}
> > +	return 0;
> 
> Doesn't this need some locking?

Oops.  Yes.  It used to be inside the lock_kernel() section, but has since
escaped.

> Do you allow upgrades and downgrades?  (Just curious.)

AFS does not, as far as I know.  Upgrades are dangerous anyway as you can get
deadlock quite easily.

> > +		/* if we've already got a readlock on the server and no waiting
> > +		 * writelocks, then we might be able to instantly grant another
> 
> Is that comment correct?  (You don't really test for "waiting
> writelocks", do you?)

Locally, yes.  'if (list_empty(&vnode->pending_locks))' covers it quite
handily.  I can't do anything about checking the server.

David
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