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authorJianyu Zhan <nasa4836@gmail.com>2014-06-04 16:09:51 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2014-06-04 16:54:07 -0700
commitbea04b073292b2acb522c7c1aa67a4fc58151530 (patch)
tree9d4efd221e0fa4b649cc6fbcfa19baa22cb3b3be
parente9ade569910a82614ff5f2c2cea2b65a8d785da4 (diff)
downloadlinux-bea04b073292b2acb522c7c1aa67a4fc58151530.tar.bz2
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>
-rw-r--r--mm/internal.h7
-rw-r--r--mm/rmap.c11
-rw-r--r--mm/vmstat.c4
3 files changed, 20 insertions, 2 deletions
diff --git a/mm/internal.h b/mm/internal.h
index a25424a24e0c..e067984bafa0 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -201,7 +201,12 @@ static inline int mlocked_vma_newpage(struct vm_area_struct *vma,
return 0;
if (!TestSetPageMlocked(page)) {
- mod_zone_page_state(page_zone(page), NR_MLOCK,
+ /*
+ * We use the irq-unsafe __mod_zone_page_stat because this
+ * counter is not modified from interrupt context, and the pte
+ * lock is held(spinlock), which implies preemption disabled.
+ */
+ __mod_zone_page_state(page_zone(page), NR_MLOCK,
hpage_nr_pages(page));
count_vm_event(UNEVICTABLE_PGMLOCKED);
}
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;
diff --git a/mm/vmstat.c b/mm/vmstat.c
index 376bd2d21482..b37bd49bfd55 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -207,7 +207,9 @@ void set_pgdat_percpu_threshold(pg_data_t *pgdat,
}
/*
- * For use when we know that interrupts are disabled.
+ * For use when we know that interrupts are disabled,
+ * or when we know that preemption is disabled and that
+ * particular counter cannot be updated from interrupt context.
*/
void __mod_zone_page_state(struct zone *zone, enum zone_stat_item item,
int delta)