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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().

[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>
This commit is contained in:
Jianyu Zhan 2014-06-04 16:09:51 -07:00 committed by Linus Torvalds
parent e9ade56991
commit bea04b0732
3 changed files with 20 additions and 2 deletions
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7
mm/internal.h
View file

@ -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);
}

11
mm/rmap.c
View file

@ -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;

4
mm/vmstat.c
View file

@ -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)