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Subject[PATCH 09/10] mm/page_alloc: fix possible wrongly calculated freepage counter
Date
When isolating/unisolating some pageblock, we add/sub number of
pages returend by move_freepages_block() to calculate number of freepage.
But, this value is invalid for calculation, because it means number of
pages in buddy list of that migratetype rather than number of *moved*
pages. So number of freepage could be incorrect more and more whenever
calling these functions.

And, there is one more counting problem on
__test_page_isolated_in_pageblock(). move_freepages() is called, but missed
to fixup number of freepage. I think that counting should be done in
move_freepages(), otherwise, another future user to this function also
missed to fixup number of freepage again.

Now, we have proper infrastructure, get_onbuddy_migratetype(), which can
be used to get current migratetype of buddy list. So fix this situation.

Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
---
mm/page_alloc.c | 37 ++++++++++++++++++++++++++++++++++---
mm/page_isolation.c | 12 +++---------
2 files changed, 37 insertions(+), 12 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index d9fb8bb..80c9bd8 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -465,6 +465,33 @@ static inline void clear_page_guard(struct zone *zone, struct page *page,
unsigned int order, int migratetype) {}
#endif

+static inline void count_freepage_nr(struct page *page, int order,
+ int *nr_isolate, int *nr_cma, int *nr_others)
+{
+ int nr = 1 << order;
+ int migratetype = get_onbuddy_migratetype(page);
+
+ if (is_migrate_isolate(migratetype))
+ *nr_isolate += nr;
+ else if (is_migrate_cma(migratetype))
+ *nr_cma += nr;
+ else
+ *nr_others += nr;
+}
+
+static void fixup_freepage_nr(struct zone *zone, int migratetype,
+ int nr_isolate, int nr_cma, int nr_others)
+{
+ int nr_free = nr_cma + nr_others;
+
+ if (is_migrate_isolate(migratetype)) {
+ __mod_zone_page_state(zone, NR_FREE_PAGES, -nr_free);
+ __mod_zone_page_state(zone, NR_FREE_CMA_PAGES, -nr_cma);
+ } else {
+ __mod_zone_freepage_state(zone, nr_isolate, migratetype);
+ }
+}
+
static inline void set_page_order(struct page *page, unsigned int order,
int migratetype)
{
@@ -619,6 +646,7 @@ static inline void __free_one_page(struct page *page,
buddy = page + (buddy_idx - page_idx);
if (!page_is_buddy(page, buddy, order))
break;
+
/*
* Our buddy is free or it is CONFIG_DEBUG_PAGEALLOC guard page,
* merge with it and move up one order.
@@ -1062,7 +1090,7 @@ int move_freepages(struct zone *zone,
{
struct page *page;
unsigned long order;
- int pages_moved = 0;
+ int nr_pages = 0, nr_isolate = 0, nr_cma = 0, nr_others = 0;

#ifndef CONFIG_HOLES_IN_ZONE
/*
@@ -1090,14 +1118,17 @@ int move_freepages(struct zone *zone,
}

order = page_order(page);
+ count_freepage_nr(page, order,
+ &nr_isolate, &nr_cma, &nr_others);
list_move(&page->lru,
&zone->free_area[order].free_list[migratetype]);
set_onbuddy_migratetype(page, migratetype);
page += 1 << order;
- pages_moved += 1 << order;
+ nr_pages += 1 << order;
}

- return pages_moved;
+ fixup_freepage_nr(zone, migratetype, nr_isolate, nr_cma, nr_others);
+ return nr_pages;
}

int move_freepages_block(struct zone *zone, struct page *page,
diff --git a/mm/page_isolation.c b/mm/page_isolation.c
index 6e4e86b..62676de 100644
--- a/mm/page_isolation.c
+++ b/mm/page_isolation.c
@@ -56,14 +56,9 @@ int set_migratetype_isolate(struct page *page, bool skip_hwpoisoned_pages)

out:
if (!ret) {
- unsigned long nr_pages;
- int migratetype = get_pageblock_migratetype(page);
-
set_pageblock_migratetype(page, MIGRATE_ISOLATE);
zone->nr_isolate_pageblock++;
- nr_pages = move_freepages_block(zone, page, MIGRATE_ISOLATE);
-
- __mod_zone_freepage_state(zone, -nr_pages, migratetype);
+ move_freepages_block(zone, page, MIGRATE_ISOLATE);
}

spin_unlock_irqrestore(&zone->lock, flags);
@@ -75,14 +70,13 @@ out:
void unset_migratetype_isolate(struct page *page, unsigned migratetype)
{
struct zone *zone;
- unsigned long flags, nr_pages;
+ unsigned long flags;

zone = page_zone(page);
spin_lock_irqsave(&zone->lock, flags);
if (get_pageblock_migratetype(page) != MIGRATE_ISOLATE)
goto out;
- nr_pages = move_freepages_block(zone, page, migratetype);
- __mod_zone_freepage_state(zone, nr_pages, migratetype);
+ move_freepages_block(zone, page, migratetype);
set_pageblock_migratetype(page, migratetype);
zone->nr_isolate_pageblock--;
out:
--
1.7.9.5


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