From 21333b2b66b805a360641568588e5a0bb06d9d1f Mon Sep 17 00:00:00 2001
From: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Date: Mon, 21 Sep 2009 17:01:59 -0700
Subject: [PATCH] ksm: no debug in page_dup_rmap()
page_dup_rmap(), used on each mapped page when forking, was originally
just an inline atomic_inc of mapcount. 2.6.22 added CONFIG_DEBUG_VM
out-of-line checks to it, which would need to be ever-so-slightly
complicated to allow for the PageKsm() we're about to define.
But I think these checks never caught anything. And if it's coding errors
we're worried about, such checks should be in page_remove_rmap() too, not
just when forking; whereas if it's pagetable corruption we're worried
about, then they shouldn't be limited to CONFIG_DEBUG_VM.
Oh, just revert page_dup_rmap() to an inline atomic_inc of mapcount.
Signed-off-by: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Signed-off-by: Chris Wright <chrisw@redhat.com>
Signed-off-by: Izik Eidus <ieidus@redhat.com>
Cc: Nick Piggin <npiggin@suse.de>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Cc: Balbir Singh <balbir@in.ibm.com>
Cc: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Lee Schermerhorn <lee.schermerhorn@hp.com>
Cc: Avi Kivity <avi@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
include/linux/rmap.h | 6 +-----
mm/memory.c | 2 +-
mm/rmap.c | 21 ---------------------
3 files changed, 2 insertions(+), 27 deletions(-)
diff --git a/include/linux/rmap.h b/include/linux/rmap.h
index bf116d0dbf23f..477841d29fce2 100644
--- a/include/linux/rmap.h
+++ b/include/linux/rmap.h
@@ -71,14 +71,10 @@ void page_add_new_anon_rmap(struct page *, struct vm_area_struct *, unsigned lon
void page_add_file_rmap(struct page *);
void page_remove_rmap(struct page *);
-#ifdef CONFIG_DEBUG_VM
-void page_dup_rmap(struct page *page, struct vm_area_struct *vma, unsigned long address);
-#else
-static inline void page_dup_rmap(struct page *page, struct vm_area_struct *vma, unsigned long address)
+static inline void page_dup_rmap(struct page *page)
{
atomic_inc(&page->_mapcount);
}
-#endif
/*
* Called from mm/vmscan.c to handle paging out
diff --git a/mm/memory.c b/mm/memory.c
index 368561f32009d..7a61a11f18672 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -597,7 +597,7 @@ copy_one_pte(struct mm_struct *dst_mm, struct mm_struct *src_mm,
page = vm_normal_page(vma, addr, pte);
if (page) {
get_page(page);
- page_dup_rmap(page, vma, addr);
+ page_dup_rmap(page);
rss[!!PageAnon(page)]++;
}
diff --git a/mm/rmap.c b/mm/rmap.c
index 1406e67f96137..720fc03a7bc45 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -710,27 +710,6 @@ void page_add_file_rmap(struct page *page)
}
}
-#ifdef CONFIG_DEBUG_VM
-/**
- * page_dup_rmap - duplicate pte mapping to a page
- * @page: the page to add the mapping to
- * @vma: the vm area being duplicated
- * @address: the user virtual address mapped
- *
- * For copy_page_range only: minimal extract from page_add_file_rmap /
- * page_add_anon_rmap, avoiding unnecessary tests (already checked) so it's
- * quicker.
- *
- * The caller needs to hold the pte lock.
- */
-void page_dup_rmap(struct page *page, struct vm_area_struct *vma, unsigned long address)
-{
- if (PageAnon(page))
- __page_check_anon_rmap(page, vma, address);
- atomic_inc(&page->_mapcount);
-}
-#endif
-
/**
* page_remove_rmap - take down pte mapping from a page
* @page: page to remove mapping from
--
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