linux-kernel - Re: [PATCH 1 of 9] Lock the entire mm to prevent any mmu related operation to happen

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Date:	Fri, 25 Apr 2008 19:04:25 +0200
From:	Andrea Arcangeli <andrea@...ranet.com>
To:	Rusty Russell <rusty@...tcorp.com.au>
Cc:	Christoph Lameter <clameter@....com>, akpm@...ux-foundation.org,
	Nick Piggin <npiggin@...e.de>,
	Steve Wise <swise@...ngridcomputing.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>, linux-mm@...ck.org,
	Kanoj Sarcar <kanojsarcar@...oo.com>,
	Roland Dreier <rdreier@...co.com>,
	Jack Steiner <steiner@....com>, linux-kernel@...r.kernel.org,
	Avi Kivity <avi@...ranet.com>, kvm-devel@...ts.sourceforge.net,
	Robin Holt <holt@....com>, general@...ts.openfabrics.org,
	Hugh Dickins <hugh@...itas.com>
Subject: Re: [PATCH 1 of 9] Lock the entire mm to prevent any mmu related
	operation to happen

On Fri, Apr 25, 2008 at 06:56:39PM +0200, Andrea Arcangeli wrote:
> > > +		data->i_mmap_locks = vmalloc(nr_i_mmap_locks *
> > > +					     sizeof(spinlock_t));
> > 
> > This is why non-typesafe allocators suck.  You want 'sizeof(spinlock_t *)' 
> > here.
> > 
> > > +		data->anon_vma_locks = vmalloc(nr_anon_vma_locks *
> > > +					       sizeof(spinlock_t));
> > 
> > and here.
> 
> Great catch! (it was temporarily wasting some ram which isn't nice at all)

As I went into the editor I just found the above already fixed in
#v14-pre3. And I can't move the structure into the file anymore
without kmallocing it. Exposing that structure avoids the
ERR_PTR/PTR_ERR on the retvals and one kmalloc so I think it makes the
code simpler in the end to keep it as it is now. I'd rather avoid
further changes to the 1/N patch, as long as they don't make any
difference at runtime and as long as they involve more than
cut-and-pasting a structure from .h to .c file.
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