From bea04b073292b2acb522c7c1aa67a4fc58151530 Mon Sep 17 00:00:00 2001 From: Jianyu Zhan Date: Wed, 4 Jun 2014 16:09:51 -0700 Subject: mm: use the light version __mod_zone_page_state in mlocked_vma_newpage() mlocked_vma_newpage() is called with pte lock held(a spinlock), which implies preemtion disabled, and the vm stat counter is not modified from interrupt context, so we need not use an irq-safe mod_zone_page_state() here, using a light-weight version __mod_zone_page_state() would be OK. This patch also documents __mod_zone_page_state() and some of its callsites. The comment above __mod_zone_page_state() is from Hugh Dickins, and acked by Christoph. Most credits to Hugh and Christoph for the clarification on the usage of the __mod_zone_page_state(). [akpm@linux-foundation.org: coding-style fixes] Suggested-by: Andrew Morton Acked-by: Hugh Dickins Signed-off-by: Jianyu Zhan Reviewed-by: Christoph Lameter Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/rmap.c | 11 +++++++++++ 1 file changed, 11 insertions(+) (limited to 'mm/rmap.c') diff --git a/mm/rmap.c b/mm/rmap.c index 8754e1fa83b6..4644e10248f0 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -988,6 +988,12 @@ void do_page_add_anon_rmap(struct page *page, { int first = atomic_inc_and_test(&page->_mapcount); if (first) { + /* + * We use the irq-unsafe __{inc|mod}_zone_page_stat because + * these counters are not modified in interrupt context, and + * pte lock(a spinlock) is held, which implies preemption + * disabled. + */ if (PageTransHuge(page)) __inc_zone_page_state(page, NR_ANON_TRANSPARENT_HUGEPAGES); @@ -1079,6 +1085,11 @@ void page_remove_rmap(struct page *page) /* * Hugepages are not counted in NR_ANON_PAGES nor NR_FILE_MAPPED * and not charged by memcg for now. + * + * We use the irq-unsafe __{inc|mod}_zone_page_stat because + * these counters are not modified in interrupt context, and + * these counters are not modified in interrupt context, and + * pte lock(a spinlock) is held, which implies preemption disabled. */ if (unlikely(PageHuge(page))) goto out; -- cgit v1.2.3