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Wed, 05 Feb 2020 17:16:23 -0800 (PST) MIME-Version: 1.0 References: <1580922215-5272-1-git-send-email-laoar.shao@gmail.com> <1ef8ee2e-0f50-fcd6-ae13-d6524fcf9764@redhat.com> In-Reply-To: <1ef8ee2e-0f50-fcd6-ae13-d6524fcf9764@redhat.com> From: Yafang Shao Date: Thu, 6 Feb 2020 09:15:47 +0800 Message-ID: Subject: Re: [PATCH] mm, memcg: fix build error around the usage of kmem_caches To: David Hildenbrand Cc: Tejun Heo , Vladimir Davydov , Johannes Weiner , Michal Hocko , Andrew Morton , Christoph Lameter , penberg@kernel.org, David Rientjes , iamjoonsoo.kim@lge.com, Cgroups , Linux MM Content-Type: text/plain; charset="UTF-8" X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, Feb 6, 2020 at 1:19 AM David Hildenbrand wrote: > > On 05.02.20 18:03, Yafang Shao wrote: > > When I manually set default n to MEMCG_KMEM in init/Kconfig, bellow error > > occurs, > > > > mm/slab_common.c: In function 'memcg_slab_start': > > mm/slab_common.c:1530:30: error: 'struct mem_cgroup' has no member named > > 'kmem_caches' > > return seq_list_start(&memcg->kmem_caches, *pos); > > ^ > > mm/slab_common.c: In function 'memcg_slab_next': > > mm/slab_common.c:1537:32: error: 'struct mem_cgroup' has no member named > > 'kmem_caches' > > return seq_list_next(p, &memcg->kmem_caches, pos); > > ^ > > mm/slab_common.c: In function 'memcg_slab_show': > > mm/slab_common.c:1551:16: error: 'struct mem_cgroup' has no member named > > 'kmem_caches' > > if (p == memcg->kmem_caches.next) > > ^ > > CC arch/x86/xen/smp.o > > mm/slab_common.c: In function 'memcg_slab_start': > > mm/slab_common.c:1531:1: warning: control reaches end of non-void function > > [-Wreturn-type] > > } > > ^ > > mm/slab_common.c: In function 'memcg_slab_next': > > mm/slab_common.c:1538:1: warning: control reaches end of non-void function > > [-Wreturn-type] > > } > > ^ > > > > That's because kmem_caches is defined only when CONFIG_MEMCG_KMEM is set, > > while memcg_slab_start() will use it no matter CONFIG_MEMCG_KMEM is defined > > or not. > > > > By the way, the reason I mannuly undefined CONFIG_MEMCG_KMEM is to verify > > whether my some other code change is still stable when CONFIG_MEMCG_KMEM is > > not set. Unfortunately, the existing code has been already unstable since > > v4.11. > > > > Fixes: bc2791f857e1 ("slab: link memcg kmem_caches on their associated memory cgroup") > > Cc: Tejun Heo > > Cc: Vladimir Davydov > > Signed-off-by: Yafang Shao > > --- > > mm/memcontrol.c | 2 ++ > > mm/slab_common.c | 2 +- > > 2 files changed, 3 insertions(+), 1 deletion(-) > > > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > > index 6f6dc8712e39..43f0125b45bb 100644 > > --- a/mm/memcontrol.c > > +++ b/mm/memcontrol.c > > @@ -4723,6 +4723,7 @@ static struct cftype mem_cgroup_legacy_files[] = { > > .write = mem_cgroup_reset, > > .read_u64 = mem_cgroup_read_u64, > > }, > > +#ifdef CONFIG_MEMCG_KMEM > > #if defined(CONFIG_SLAB) || defined(CONFIG_SLUB_DEBUG) > > Not sure if > > #if defined(CONFIG_MEMCG_KMEM) && \ > (defined(CONFIG_SLAB) || defined(CONFIG_SLUB_DEBUG)) > > is preffered > Seems better. Thanks for your suggestion. Thanks Yafang