[PATCH] memcg: avoid overflow in memcg_hierarchical_free_pages()

Greg Thelen
2010-11-09T01:16:33Z

Use page counts rather than byte counts to avoid overflowing
unsigned long local variables.

Signed-off-by: Greg Thelen <gthelen@google.com>
---
mm/memcontrol.c | 10 +++++-----
1 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 6c7115d..b287afd 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1345,17 +1345,17 @@ memcg_hierarchical_free_pages(struct mem_cgroup *mem)
{
unsigned long free, min_free;

- min_free = global_page_state(NR_FREE_PAGES) << PAGE_SHIFT;
+ min_free = global_page_state(NR_FREE_PAGES);

while (mem) {
- free = res_counter_read_u64(&mem->res, RES_LIMIT) -
- res_counter_read_u64(&mem->res, RES_USAGE);
+ free = (res_counter_read_u64(&mem->res, RES_LIMIT) -
+ res_counter_read_u64(&mem->res, RES_USAGE)) >>
+ PAGE_SHIFT;
min_free = min(min_free, free);
mem = parent_mem_cgroup(mem);
}

- /* Translate free memory in pages */
- return min_free >> PAGE_SHIFT;
+ return min_free;
}

/*
--
1.7.3.1