[PATCH 06/11] mm: page_counter: constify page_counter_read() and page_counter_margin()

[Tal Zussman <tz2294@columbia.edu>]

Both only read the counter. Constify them so that users can read
counters from const memcgs.

Signed-off-by: Tal Zussman <tz2294@columbia.edu>
---
 include/linux/page_counter.h | 4 ++--
 mm/page_counter.c            | 2 +-
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/include/linux/page_counter.h b/include/linux/page_counter.h
index 07b7cb12249c..2baf7a2b29b2 100644
--- a/include/linux/page_counter.h
+++ b/include/linux/page_counter.h
@@ -63,12 +63,12 @@ static inline void page_counter_init(struct page_counter *counter,
 	counter->track_failcnt = false;
 }
 
-static inline unsigned long page_counter_read(struct page_counter *counter)
+static inline unsigned long page_counter_read(const struct page_counter *counter)
 {
 	return atomic_long_read(&counter->usage);
 }
 
-long page_counter_margin(struct page_counter *counter);
+long page_counter_margin(const struct page_counter *counter);
 void page_counter_cancel(struct page_counter *counter, unsigned long nr_pages);
 void page_counter_charge(struct page_counter *counter, unsigned long nr_pages);
 bool page_counter_try_charge(struct page_counter *counter,
diff --git a/mm/page_counter.c b/mm/page_counter.c
index 450543f4b318..8c6f3b45136b 100644
--- a/mm/page_counter.c
+++ b/mm/page_counter.c
@@ -53,7 +53,7 @@ static void propagate_protected_usage(struct page_counter *c,
  * Return: The minimum value of max minus usage across @counter and all of
  * its ancestors. The value may be negative during a concurrent charge.
  */
-long page_counter_margin(struct page_counter *counter)
+long page_counter_margin(const struct page_counter *counter)
 {
 	long margin = PAGE_COUNTER_MAX;
 

-- 
2.39.5