Re: [PATCH v4 5/7] mm: rework non-root kmem_cache lifecycle management

From: Roman Gushchin <guro@fb.com>
To: Waiman Long <longman9394@gmail.com>
Cc: Shakeel Butt <shakeelb@google.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Linux MM <linux-mm@kvack.org>,
	LKML <linux-kernel@vger.kernel.org>,
	Kernel Team <Kernel-team@fb.com>,
	"Johannes Weiner" <hannes@cmpxchg.org>,
	Michal Hocko <mhocko@kernel.org>, Rik van Riel <riel@surriel.com>,
	Christoph Lameter <cl@linux.com>,
	Vladimir Davydov <vdavydov.dev@gmail.com>,
	Cgroups <cgroups@vger.kernel.org>
Subject: Re: [PATCH v4 5/7] mm: rework non-root kmem_cache lifecycle management
Date: Mon, 20 May 2019 17:56:46 +0000	[thread overview]
Message-ID: <20190520175640.GA24204@tower.DHCP.thefacebook.com> (raw)
In-Reply-To: <5e3c4646-3e4f-414a-0eca-5249956d68a5@gmail.com>

On Mon, May 20, 2019 at 10:54:24AM -0400, Waiman Long wrote:
> On 5/14/19 8:06 PM, Shakeel Butt wrote:
> > diff --git a/mm/slab_common.c b/mm/slab_common.c
> > index 4e5b4292a763..1ee967b4805e 100644
> > --- a/mm/slab_common.c
> > +++ b/mm/slab_common.c
> > @@ -45,6 +45,8 @@ static void slab_caches_to_rcu_destroy_workfn(struct work_struct *work);
> >  static DECLARE_WORK(slab_caches_to_rcu_destroy_work,
> >                     slab_caches_to_rcu_destroy_workfn);
> >
> > +static void kmemcg_queue_cache_shutdown(struct percpu_ref *percpu_ref);
> > +
> 
> kmemcg_queue_cache_shutdown is only defined if CONFIG_MEMCG_KMEM is
> defined. If it is not defined, a compilation warning can be produced.
> Maybe putting the declaration inside a CONFIG_MEMCG_KMEM block:

Hi Waiman!

Yes, that makes total sense to me. Thank you for letting me know!
How about this one?

--

From 0fa19369adc240cc93281911a59713822a4f3e07 Mon Sep 17 00:00:00 2001
From: Roman Gushchin <guro@fb.com>
Date: Mon, 20 May 2019 10:52:07 -0700
Subject: [PATCH] mm: guard kmemcg_queue_cache_shutdown() with
 CONFIG_MEMCG_KMEM

Currently kmemcg_queue_cache_shutdown() is defined only
if CONFIG_MEMCG_KMEM is set, however the declaration is not guarded
with corresponding ifdefs. So a compilation warning might be produced.

Let's move the declaration to the section of slab_common.c, where all
kmemcg-specific stuff is defined.

Reported-by: Waiman Long <longman9394@gmail.com>
Signed-off-by: Roman Gushchin <guro@fb.com>
---
 mm/slab_common.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/mm/slab_common.c b/mm/slab_common.c
index 9d2a3d6245dc..e818609c8209 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -45,8 +45,6 @@ static void slab_caches_to_rcu_destroy_workfn(struct work_struct *work);
 static DECLARE_WORK(slab_caches_to_rcu_destroy_work,
 		    slab_caches_to_rcu_destroy_workfn);
 
-static void kmemcg_queue_cache_shutdown(struct percpu_ref *percpu_ref);
-
 /*
  * Set of flags that will prevent slab merging
  */
@@ -134,6 +132,8 @@ int __kmem_cache_alloc_bulk(struct kmem_cache *s, gfp_t flags, size_t nr,
 LIST_HEAD(slab_root_caches);
 static DEFINE_SPINLOCK(memcg_kmem_wq_lock);
 
+static void kmemcg_queue_cache_shutdown(struct percpu_ref *percpu_ref);
+
 void slab_init_memcg_params(struct kmem_cache *s)
 {
 	s->memcg_params.root_cache = NULL;
-- 
2.20.1
