linux-kernel - Re: [PATCH 1/3] mm: use long type for page counts in mm_populate() and get_user

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Message-Id: <20130130164220.eaebcb6a.akpm@linux-foundation.org>
Date:	Wed, 30 Jan 2013 16:42:20 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Michel Lespinasse <walken@...gle.com>
Cc:	Andrea Arcangeli <aarcange@...hat.com>,
	Rik van Riel <riel@...hat.com>, Mel Gorman <mgorman@...e.de>,
	Hugh Dickins <hughd@...gle.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] mm: use long type for page counts in mm_populate()
 and get_user_pages()

On Wed, 30 Jan 2013 16:26:18 -0800
Michel Lespinasse <walken@...gle.com> wrote:

> Use long type for page counts in mm_populate() so as to avoid integer
> overflow

Would prefer to use unsigned long if we're churning this code.  A "page
count" can never be negative and we avoid the various possible
overflow/signedness issues.

However get_user_pages() and follow_hugetlb_page() return "page count
or -ve errno", so we're somewhat screwed there.  And that's the bulk of
the patch :(

btw, what twit merged a follow_hugetlb_page() which takes an
undocumented argument called "i".  Sigh.

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