percpu-refcount: Add a WARN() for ref going negative
AIO had a missing get, which led to an ioctx leak - after percpu_ref_kill() the
ref was 0 so percpu_ref_put() never saw it hit 0.
This wasn't noticed at the time because it all happened completely silently,
this adds a WARN() which would've caught the aio bug.
tj: Used WARN_ONCE() instead of WARN().
Signed-off-by: Kent Overstreet <kmo@daterainc.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
diff --git a/lib/percpu-refcount.c b/lib/percpu-refcount.c
index 1a53d49..963b703 100644
--- a/lib/percpu-refcount.c
+++ b/lib/percpu-refcount.c
@@ -120,6 +120,9 @@
atomic_add((int) count - PCPU_COUNT_BIAS, &ref->count);
+ WARN_ONCE(atomic_read(&ref->count) <= 0, "percpu ref <= 0 (%i)",
+ atomic_read(&ref->count));
+
/* @ref is viewed as dead on all CPUs, send out kill confirmation */
if (ref->confirm_kill)
ref->confirm_kill(ref);