From 687b0ad2751ca8ea418396fa780e22571fba76a8 Mon Sep 17 00:00:00 2001 From: Kent Overstreet Date: Mon, 6 Jan 2014 13:13:26 -0800 Subject: [PATCH 1/2] 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 Signed-off-by: Tejun Heo --- lib/percpu-refcount.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/lib/percpu-refcount.c b/lib/percpu-refcount.c index 1a53d497a8c5..963b7034a51b 100644 --- a/lib/percpu-refcount.c +++ b/lib/percpu-refcount.c @@ -120,6 +120,9 @@ static void percpu_ref_kill_rcu(struct rcu_head *rcu) 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); From 8a0921712ec6d00754b5d7afea78137772efee0a Mon Sep 17 00:00:00 2001 From: Laura Abbott Date: Thu, 2 Jan 2014 13:53:21 -0800 Subject: [PATCH 2/2] percpu: use VMALLOC_TOTAL instead of VMALLOC_END - VMALLOC_START vmalloc already gives a useful macro to calculate the total vmalloc size. Use it. Signed-off-by: Laura Abbott Signed-off-by: Tejun Heo --- mm/percpu.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/mm/percpu.c b/mm/percpu.c index 0d10defe951e..afbf352ae580 100644 --- a/mm/percpu.c +++ b/mm/percpu.c @@ -1686,10 +1686,10 @@ int __init pcpu_embed_first_chunk(size_t reserved_size, size_t dyn_size, max_distance += ai->unit_size; /* warn if maximum distance is further than 75% of vmalloc space */ - if (max_distance > (VMALLOC_END - VMALLOC_START) * 3 / 4) { + if (max_distance > VMALLOC_TOTAL * 3 / 4) { pr_warning("PERCPU: max_distance=0x%zx too large for vmalloc " "space 0x%lx\n", max_distance, - (unsigned long)(VMALLOC_END - VMALLOC_START)); + VMALLOC_TOTAL); #ifdef CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK /* and fail if we have fallback */ rc = -EINVAL;