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authorJianyu Zhan <nasa4836@gmail.com>2014-06-05 03:09:51 +0400
committerLinus Torvalds <torvalds@linux-foundation.org>2014-06-05 03:54:07 +0400
commitbea04b073292b2acb522c7c1aa67a4fc58151530 (patch)
tree9d4efd221e0fa4b649cc6fbcfa19baa22cb3b3be /mm/rmap.c
parente9ade569910a82614ff5f2c2cea2b65a8d785da4 (diff)
downloadlinux-bea04b073292b2acb522c7c1aa67a4fc58151530.tar.xz
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 <akpm@linux-foundation.org> Acked-by: Hugh Dickins <hughd@google.com> Signed-off-by: Jianyu Zhan <nasa4836@gmail.com> Reviewed-by: Christoph Lameter <cl@linux.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/rmap.c')
-rw-r--r--mm/rmap.c11
1 files changed, 11 insertions, 0 deletions
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;