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mm: use the light version __mod_zone_page_state in mlocked_vma_newpage()

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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().

[[email protected]: coding-style fixes]
Suggested-by: Andrew Morton <[email protected]>
Acked-by: Hugh Dickins <[email protected]>
Signed-off-by: Jianyu Zhan <[email protected]>
Reviewed-by: Christoph Lameter <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
This commit is contained in:
Jianyu Zhan 2014-06-04 16:09:51 -07:00 • committed by Linus Torvalds
commit bea04b0732
3 changed files with 20 additions and 2 deletions
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11
mm/rmap.c
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@ -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;