[Devel] [PATCH RHEL7 COMMIT] memcg: add mem_cgroup_get/put helpers

[Konstantin Khorenko]

The commit is pushed to "branch-rh7-3.10.0-229.7.2.vz7.8.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh7-3.10.0-229.7.2.vz7.8.6
------>
commit 28d232fd4095c371daa0980f5fae9642a30780b1
Author: Vladimir Davydov <vdavydov at parallels.com>
Date:   Thu Oct 15 17:52:58 2015 +0400

    memcg: add mem_cgroup_get/put helpers
    
    Patchset description: oom enhancements - part 2
    
     - Patches 1-2 prepare memcg for upcoming changes in oom design.
     - Patch 3 reworks oom locking design so that the executioner waits for
       victim to exit. This is necessary to increase oom kill rate, which is
       essential for berserker mode.
     - Patch 4 drops unused OOM_SCAN_ABORT
     - Patch 5 introduces oom timeout.
       https://jira.sw.ru/browse/PSBM-38581
     - Patch 6 makes oom fairer when it comes to selecting a victim among
       different containers.
       https://jira.sw.ru/browse/PSBM-37915
     - Patch 7 prepares oom for introducing berserker mode
     - Patch 8 resurrects oom berserker mode, which is supposed to cope with
       actively forking processes.
       https://jira.sw.ru/browse/PSBM-17930
    
    https://jira.sw.ru/browse/PSBM-26973
    
    Changes in v3:
     - rework oom_trylock (patch 3)
     - select exiting process instead of aborting oom scan so as not to keep
       busy-waiting for an exiting process to exit (patches 3, 4)
     - cleanup oom timeout handling + fix stuck process trace dumped
       multiple times on timeout (patch 5)
     - set max_overdraft to ULONG_MAX on selected processes (patch 6)
     - rework oom berserker process selection logic (patches 7, 8)
    
    Changes in v2:
     - s/time_after/time_after_eq to avoid BUG_ON in oom_trylock (patch 4)
     - propagate victim to the context that initiated oom in oom_unlock
       (patch 6)
     - always set oom_end on releasing oom context (patch 6)
    
    Vladimir Davydov (8):
      memcg: add mem_cgroup_get/put helpers
      memcg: add lock for protecting memcg->oom_notify list
      oom: rework locking design
      oom: introduce oom timeout
      oom: drop OOM_SCAN_ABORT
      oom: rework logic behind memory.oom_guarantee
      oom: pass points and overdraft to oom_kill_process
      oom: resurrect berserker mode
    
    Reviewed-by: Kirill Tkhai <ktkhai at odin.com>
    
    =========================================
    This patch description:
    
    Equivalent to css_get/put(mem_cgroup_css(memcg)). Currently, only used
    by af_packet.c, but will also be used by the following patches.
    
    Signed-off-by: Vladimir Davydov <vdavydov at parallels.com>
---
 include/linux/memcontrol.h | 18 ++++++++++++++++++
 net/packet/af_packet.c     |  4 ++--
 2 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index ac3f16f..548a82c 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -139,6 +139,16 @@ static inline bool mem_cgroup_disabled(void)
 	return false;
 }
 
+static inline void mem_cgroup_get(struct mem_cgroup *memcg)
+{
+	css_get(mem_cgroup_css(memcg));
+}
+
+static inline void mem_cgroup_put(struct mem_cgroup *memcg)
+{
+	css_put(mem_cgroup_css(memcg));
+}
+
 void __mem_cgroup_begin_update_page_stat(struct page *page, bool *locked,
 					 unsigned long *flags);
 
@@ -321,6 +331,14 @@ static inline bool mem_cgroup_disabled(void)
 	return true;
 }
 
+static inline void mem_cgroup_get(struct mem_cgroup *memcg)
+{
+}
+
+static inline void mem_cgroup_put(struct mem_cgroup *memcg)
+{
+}
+
 static inline int
 mem_cgroup_inactive_anon_is_low(struct lruvec *lruvec)
 {
diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index ee9d56b..0bc235e 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -2524,7 +2524,7 @@ static struct cg_proto *packet_sk_charge(void)
 		goto out;
 
 out_put_cg:
-	css_put(mem_cgroup_css(psc->memcg));
+	mem_cgroup_put(psc->memcg);
 out_free_psc:
 	kfree(psc);
 	psc = NULL;
@@ -2545,7 +2545,7 @@ static void packet_sk_uncharge(struct cg_proto *cg)
 
 	if (psc) {
 		memcg_uncharge_kmem(psc->memcg, psc->amt);
-		css_put(mem_cgroup_css(psc->memcg));
+		mem_cgroup_put(psc->memcg);
 		kfree(psc);
 	}
 }