rmap: move exclusively owned pages to own anon_vma in do_wp_page()
authorRik van Riel <riel@redhat.com>
Fri, 5 Mar 2010 21:42:09 +0000 (13:42 -0800)
committerLinus Torvalds <torvalds@linux-foundation.org>
Sat, 6 Mar 2010 19:26:26 +0000 (11:26 -0800)
commitc44b674323f4a2480dbeb65d4b487fa5f06f49e0
treeb753050e6752eb2fc961ad3ea5dfdf88ef88364d
parent033a64b56aed798991de18d226085dfb1ccd858d
rmap: move exclusively owned pages to own anon_vma in do_wp_page()

When the parent process breaks the COW on a page, both the original which
is mapped at child and the new page which is mapped parent end up in that
same anon_vma.  Generally this won't be a problem, but for some workloads
it could preserve the O(N) rmap scanning complexity.

A simple fix is to ensure that, when a page which is mapped child gets
reused in do_wp_page, because we already are the exclusive owner, the page
gets moved to our own exclusive child's anon_vma.

Signed-off-by: Rik van Riel <riel@redhat.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Larry Woodman <lwoodman@redhat.com>
Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com>
Reviewed-by: Minchan Kim <minchan.kim@gmail.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
include/linux/rmap.h
mm/memory.c
mm/rmap.c