Subject: Re: [PATCH 3/3] mm: memcontrol: consolidate cgroup socket tracking

From: Johannes Weiner <[email-masked]>
Date: Thu, 15 Sep 2016 10:27:33 -0400

On Wed, Sep 14, 2016 at 03:17:14PM -0700, Andrew Morton wrote:
> On Thu, 15 Sep 2016 13:34:24 +0800 kbuild test robot <[email-masked]> wrote:
> 
> > Hi Johannes,
> > 
> > [auto build test ERROR on net/master]
> > [also build test ERROR on v4.8-rc6 next-20160914]
> > [if your patch is applied to the wrong git tree, please drop us a note to help improve the system]
> > [Suggest to use git(>=2.9.0) format-patch --base=<commit> (or --base=auto for convenience) to record what (public, well-known) commit your patch series was built on]
> > [Check https://git-scm.com/docs/git-format-patch for more information]
> > 
> > url:    https://github.com/0day-ci/linux/commits/Johannes-Weiner/mm-memcontrol-make-per-cpu-charge-cache-IRQ-safe-for-socket-accounting/20160915-035634
> > config: m68k-sun3_defconfig (attached as .config)
> > compiler: m68k-linux-gcc (GCC) 4.9.0
> > reproduce:
> >         wget https://git.kernel.org/cgit/linux/kernel/git/wfg/lkp-tests.git/plain/sbin/make.cross -O ~/bin/make.cross
> >         chmod +x ~/bin/make.cross
> >         # save the attached .config to linux build tree
> >         make.cross ARCH=m68k 
> > 
> > All errors (new ones prefixed by >>):
> > 
> >    net/built-in.o: In function `sk_alloc':
> > >> (.text+0x4076): undefined reference to `mem_cgroup_sk_alloc'
> >    net/built-in.o: In function `__sk_destruct':
> > >> sock.c:(.text+0x457e): undefined reference to `mem_cgroup_sk_free'
> >    net/built-in.o: In function `sk_clone_lock':
> >    (.text+0x4f1c): undefined reference to `mem_cgroup_sk_alloc'
> 
> This?

Thanks for fixing it up, Andrew.

I think it'd be nicer to declare the dummy functions for !CONFIG_MEMCG;
it also doesn't look like a hotpath that would necessitate the jump
label in that place. Dave, any preference either way?

Signed-off-by: Johannes Weiner <[email-masked]>
---

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index ca11b3e6dd65..61d20c17f3b7 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -773,13 +773,13 @@ static inline void mem_cgroup_wb_stats(struct bdi_writeback *wb,
 #endif	/* CONFIG_CGROUP_WRITEBACK */
 
 struct sock;
-void mem_cgroup_sk_alloc(struct sock *sk);
-void mem_cgroup_sk_free(struct sock *sk);
 bool mem_cgroup_charge_skmem(struct mem_cgroup *memcg, unsigned int nr_pages);
 void mem_cgroup_uncharge_skmem(struct mem_cgroup *memcg, unsigned int nr_pages);
 #ifdef CONFIG_MEMCG
 extern struct static_key_false memcg_sockets_enabled_key;
 #define mem_cgroup_sockets_enabled static_branch_unlikely(&memcg_sockets_enabled_key)
+void mem_cgroup_sk_alloc(struct sock *sk);
+void mem_cgroup_sk_free(struct sock *sk);
 static inline bool mem_cgroup_under_socket_pressure(struct mem_cgroup *memcg)
 {
 	if (!cgroup_subsys_on_dfl(memory_cgrp_subsys) && memcg->tcpmem_pressure)
@@ -792,6 +792,8 @@ static inline bool mem_cgroup_under_socket_pressure(struct mem_cgroup *memcg)
 }
 #else
 #define mem_cgroup_sockets_enabled 0
+static inline void mem_cgroup_sk_alloc(struct sock *sk) { };
+static inline void mem_cgroup_sk_free(struct sock *sk) { };
 static inline bool mem_cgroup_under_socket_pressure(struct mem_cgroup *memcg)
 {
 	return false;