[PATCH 1/8] mm: page_counter: let page_counter_try_charge() return bool

Johannes Weiner
2015-10-22T04:25:05Z

page_counter_try_charge() currently returns 0 on success and -ENOMEM
on failure, which is surprising behavior given the function name.

Make it follow the expected pattern of try_stuff() functions that
return a boolean true to indicate success, or false for failure.

Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
---
include/linux/page_counter.h | 6 +++---
mm/hugetlb_cgroup.c | 3 ++-
mm/memcontrol.c | 11 +++++------
mm/page_counter.c | 14 +++++++-------
4 files changed, 17 insertions(+), 17 deletions(-)

diff --git a/include/linux/page_counter.h b/include/linux/page_counter.h
index 17fa4f8..7e62920 100644
--- a/include/linux/page_counter.h
+++ b/include/linux/page_counter.h
@@ -36,9 +36,9 @@ static inline unsigned long page_counter_read(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);
-int page_counter_try_charge(struct page_counter *counter,
- unsigned long nr_pages,
- struct page_counter **fail);
+bool page_counter_try_charge(struct page_counter *counter,
+ unsigned long nr_pages,
+ struct page_counter **fail);
void page_counter_uncharge(struct page_counter *counter, unsigned long nr_pages);
int page_counter_limit(struct page_counter *counter, unsigned long limit);
int page_counter_memparse(const char *buf, const char *max,
diff --git a/mm/hugetlb_cgroup.c b/mm/hugetlb_cgroup.c
index 6a44263..d8fb10d 100644
--- a/mm/hugetlb_cgroup.c
+++ b/mm/hugetlb_cgroup.c
@@ -186,7 +186,8 @@ again:
}
rcu_read_unlock();

- ret = page_counter_try_charge(&h_cg->hugepage[idx], nr_pages, &counter);
+ if (!page_counter_try_charge(&h_cg->hugepage[idx], nr_pages, &counter))
+ ret = -ENOMEM;
css_put(&h_cg->css);
done:
*ptr = h_cg;
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index c71fe40..a8ccdbc 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2018,8 +2018,8 @@ retry:
return 0;

if (!do_swap_account ||
- !page_counter_try_charge(&memcg->memsw, batch, &counter)) {
- if (!page_counter_try_charge(&memcg->memory, batch, &counter))
+ page_counter_try_charge(&memcg->memsw, batch, &counter)) {
+ if (page_counter_try_charge(&memcg->memory, batch, &counter))
goto done_restock;
if (do_swap_account)
page_counter_uncharge(&memcg->memsw, batch);
@@ -2383,14 +2383,13 @@ int __memcg_kmem_charge_memcg(struct page *page, gfp_t gfp, int order,
{
unsigned int nr_pages = 1 << order;
struct page_counter *counter;
- int ret = 0;
+ int ret;

if (!memcg_kmem_is_active(memcg))
return 0;

- ret = page_counter_try_charge(&memcg->kmem, nr_pages, &counter);
- if (ret)
- return ret;
+ if (!page_counter_try_charge(&memcg->kmem, nr_pages, &counter))
+ return -ENOMEM;

ret = try_charge(memcg, gfp, nr_pages);
if (ret) {
diff --git a/mm/page_counter.c b/mm/page_counter.c
index 11b4bed..7c6a63d 100644
--- a/mm/page_counter.c
+++ b/mm/page_counter.c
@@ -56,12 +56,12 @@ void page_counter_charge(struct page_counter *counter, unsigned long nr_pages)
* @nr_pages: number of pages to charge
* @fail: points first counter to hit its limit, if any
*
- * Returns 0 on success, or -ENOMEM and @fail if the counter or one of
- * its ancestors has hit its configured limit.
+ * Returns %true on success, or %false and @fail if the counter or one
+ * of its ancestors has hit its configured limit.
*/
-int page_counter_try_charge(struct page_counter *counter,
- unsigned long nr_pages,
- struct page_counter **fail)
+bool page_counter_try_charge(struct page_counter *counter,
+ unsigned long nr_pages,
+ struct page_counter **fail)
{
struct page_counter *c;

@@ -99,13 +99,13 @@ int page_counter_try_charge(struct page_counter *counter,
if (new > c->watermark)
c->watermark = new;
}
- return 0;
+ return true;

failed:
for (c = counter; c != *fail; c = c->parent)
page_counter_cancel(c, nr_pages);

- return -ENOMEM;
+ return false;
}

/**
--
2.6.1