linux-kernel - Re: [PATCH] Remove BKL from fs/locks.c

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Date:	Thu, 16 Sep 2010 10:10:48 -0400
From:	"J. Bruce Fields" <bfields@...ldses.org>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	Trond Myklebust <Trond.Myklebust@...app.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	Matthew Wilcox <willy@...ux.intel.com>,
	Christoph Hellwig <hch@....de>,
	Miklos Szeredi <mszeredi@...e.cz>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Ingo Molnar <mingo@...hat.com>, John Kacur <jkacur@...hat.com>,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH] Remove BKL from fs/locks.c

On Thu, Sep 16, 2010 at 10:28:56AM +0200, Arnd Bergmann wrote:
> On Wednesday 15 September 2010 22:42:03 J. Bruce Fields wrote:
> > Looking over the server code....  The only code I see under the BKL is:
> > 
> >         - a few lease callbacks in fs/nfsd/nfs4state.c, none of which
> >           sleep at this point, so all should be fine under a spinlock or
> >           whatever we want.
> >         - fs/nfsd/nfs4state.c:check_for_locks(), which explicitly takes
> >           the BKL itself.  All it does, though, is walk the lock list
> >           for a given file and check whether any of them have a given
> >           owner.  It would be trivial to put it under some other lock
> >           and/or move it to locks.c.
> 
> Ok. In the version of the patch I sent out yesterday, I came to the
> same conclusion and put both of these under lock_flocks(), which
> is still the BKL but can be converted to a spinlock after we have
> sorted out ceph and lockd. If you and others are fine with this patch,
> I'll add it to my bkl/config series.
> 
> Note that walking the i_flock list needs to use lock_flocks()
> (or the BKL), not a private lock. I guess that's what you are saying
> anyway, just making sure.

Yes, that's fine.

--b.
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