linux-kernel - Re: [PATCH] Ensure that walk_page_range()'s start and end are page-aligned

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Message-ID: <874nuy31hw.fsf@caffeine.danplanet.com>
Date:	Fri, 10 Feb 2012 11:57:31 -0800
From:	Dan Smith <danms@...ibm.com>
To:	"Michal Nazarewicz" <mina86@...a86.com>
Cc:	akpm@...ux-foundation.org, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Ensure that walk_page_range()'s start and end are page-aligned

MN> Commit message says about walk_pte_range() but commit changes
MN> walk_page_range().

Yep, the issue occurs in walk_pte_range(). The goal was to ensure that
the external interface to it (which is walk_page_range()) does the check
and avoids doing the walk entirely. I think the expectation is that
walk_page_range() is used on aligned addresses. If we put the check in
walk_pte_range() then only walks with a pte_entry handler would fail on
unaligned addresses, which is potentially confusing.

MN> So why not change the condition to addr < end?

That would work, of course, but seems sloppier and less precise. The
existing code was clearly written expecting to walk aligned addresses.

-- 
Dan Smith
IBM Linux Technology Center
email: danms@...ibm.com
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