From: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Date: Tue, 15 Dec 2009 01:59:17 +0000 (-0800)
Subject: ksm: remove redundancies when merging page
X-Git-Tag: v2.6.33-rc1~210
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=31e855ea7173bdb0520f9684580423a9560f66e0;p=pandora-kernel.git

ksm: remove redundancies when merging page

There is no need for replace_page() to calculate a write-protected prot
vm_page_prot must already be write-protected for an anonymous page (see
mm/memory.c do_anonymous_page() for similar reliance on vm_page_prot).

There is no need for try_to_merge_one_page() to get_page and put_page on
newpage and oldpage: in every case we already hold a reference to each of
them.

But some instinct makes me move try_to_merge_one_page()'s unlock_page of
oldpage down after replace_page(): that doesn't increase contention on the
ksm page, and makes thinking about the transition easier.

Signed-off-by: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Cc: Izik Eidus <ieidus@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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