From 6d7779538f765963ced45a3fa4bed7ba8d2c277d Mon Sep 17 00:00:00 2001
From: Christoph Lameter <clameter@sgi.com>
Date: Sun, 6 May 2007 14:49:40 -0700
Subject: [PATCH] mm: optimize compound_head() by avoiding a shared page flag

The patch adds PageTail(page) and PageHead(page) to check if a page is the
head or the tail of a compound page.  This is done by masking the two bits
describing the state of a compound page and then comparing them.  So one
comparision and a branch instead of two bit checks and two branches.

Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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