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Date: Thu, 22 Mar 2012 14:26:47 -0700
From: Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH 00/16] mm: prepare for converting vm->vm_flags to 64-bit
Message-Id: <20120322142647.42395398.akpm@linux-foundation.org>
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To: Konstantin Khlebnikov <khlebnikov@openvz.org>
Cc: Minchan Kim <minchan@kernel.org>, "linux-mm@kvack.org" <linux-mm@kvack.org>, "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>, Linus Torvalds <torvalds@linux-foundation.org>, Hugh Dickins <hughd@google.com>, KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>, Ben Herrenschmidt <benh@kernel.crashing.org>, "linux@arm.linux.org.uk" <linux@arm.linux.org.uk>

On Wed, 21 Mar 2012 17:16:06 +0400
Konstantin Khlebnikov <khlebnikov@openvz.org> wrote:

> Minchan Kim wrote:
> > Hi Konstantin,
> >
> > It seems to be nice clean up to me and you are a volunteer we have been wanted
> > for a long time. Thanks!
> > I am one of people who really want to expand vm_flags to 64 bit but when KOSAKI
> > tried it, Linus said his concerning, I guess you already saw that.
> >
> > He want to tidy vm_flags's usage up rather than expanding it.
> > Without the discussion about that, just expanding vm_flags would make us use
> > it up easily so that we might need more space.
> 
> Strictly speaking, my pachset does not expands vm_flags, it just prepares to this.
> Anyway vm_flags_t looks better than hard-coded "unsigned long" and messy type-casts around it.

It would be nice to find some way of triggering compiler warnings or
sparse warnings if someone mixes a 32-bit type with a vm_flags_t.  Any
thoughts on this?

(Maybe that's what __nocast does, but Documentation/sparse.txt doesn't
describe it)

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