mm, oom: remove redundant task_in_mem_cgroup() check

oom_unkillable_task() can be called from three different contexts i.e.
global OOM, memcg OOM and oom_score procfs interface.  At the moment
oom_unkillable_task() does a task_in_mem_cgroup() check on the given
process.  Since there is no reason to perform task_in_mem_cgroup()
check for global OOM and oom_score procfs interface, those contexts
provide NULL memcg and skips the task_in_mem_cgroup() check.  However
for memcg OOM context, the oom_unkillable_task() is always called from
mem_cgroup_scan_tasks() and thus task_in_mem_cgroup() check becomes
redundant and effectively dead code.  So, just remove the
task_in_mem_cgroup() check altogether.

Link: http://lkml.kernel.org/r/20190624212631.87212-2-shakeelb@google.com
Signed-off-by: Shakeel Butt <shakeelb@google.com>
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Acked-by: Roman Gushchin <guro@fb.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Nick Piggin <npiggin@suse.de>
Cc: Paul Jackson <pj@sgi.com>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/proc/base.c b/fs/proc/base.c
index 534fb1ae498aabade3c22228ed6b960d18ed05cc..64dadd469786033dad9a2a86c48660854075648c 100644 (file)
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -532,7 +532,7 @@ static int proc_oom_score(struct seq_file *m, struct pid_namespace *ns,
        unsigned long totalpages = totalram_pages() + total_swap_pages;
        unsigned long points = 0;
 
-       points = oom_badness(task, NULL, NULL, totalpages) *
+       points = oom_badness(task, NULL, totalpages) *
                                        1000 / totalpages;
        seq_printf(m, "%lu\n", points);
 

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 68402842c3375a72bbf8ab8de6f0f73bfd0633ca..44c41462be334dac8edbc365c293d7014bed29e9 100644 (file)
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -394,7 +394,6 @@ out:
 
 struct lruvec *mem_cgroup_page_lruvec(struct page *, struct pglist_data *);
 
-bool task_in_mem_cgroup(struct task_struct *task, struct mem_cgroup *memcg);
 struct mem_cgroup *mem_cgroup_from_task(struct task_struct *p);
 
 struct mem_cgroup *get_mem_cgroup_from_mm(struct mm_struct *mm);
@@ -875,12 +874,6 @@ static inline bool mm_match_cgroup(struct mm_struct *mm,
        return true;
 }
 
-static inline bool task_in_mem_cgroup(struct task_struct *task,
-                                     const struct mem_cgroup *memcg)
-{
-       return true;
-}
-
 static inline struct mem_cgroup *get_mem_cgroup_from_mm(struct mm_struct *mm)
 {
        return NULL;

diff --git a/include/linux/oom.h b/include/linux/oom.h
index d07992009265ab6a865ba70d0f20db21e478d5df..b75104690311557b38ac474118b5f17cb87a3428 100644 (file)
--- a/include/linux/oom.h
+++ b/include/linux/oom.h
@@ -108,7 +108,7 @@ static inline vm_fault_t check_stable_address_space(struct mm_struct *mm)
 bool __oom_reap_task_mm(struct mm_struct *mm);
 
 extern unsigned long oom_badness(struct task_struct *p,
-               struct mem_cgroup *memcg, const nodemask_t *nodemask,
+               const nodemask_t *nodemask,
                unsigned long totalpages);
 
 extern bool out_of_memory(struct oom_control *oc);

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 773ae5674e127149f51c624d86448c285c1413c7..4f05735b02d3fb7a3a5ecccf601a21eaa653ddde 100644 (file)
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1259,32 +1259,6 @@ void mem_cgroup_update_lru_size(struct lruvec *lruvec, enum lru_list lru,
                *lru_size += nr_pages;
 }
 
-bool task_in_mem_cgroup(struct task_struct *task, struct mem_cgroup *memcg)
-{
-       struct mem_cgroup *task_memcg;
-       struct task_struct *p;
-       bool ret;
-
-       p = find_lock_task_mm(task);
-       if (p) {
-               task_memcg = get_mem_cgroup_from_mm(p->mm);
-               task_unlock(p);
-       } else {
-               /*
-                * All threads may have already detached their mm's, but the oom
-                * killer still needs to detect if they have already been oom
-                * killed to prevent needlessly killing additional tasks.
-                */
-               rcu_read_lock();
-               task_memcg = mem_cgroup_from_task(task);
-               css_get(&task_memcg->css);
-               rcu_read_unlock();
-       }
-       ret = mem_cgroup_is_descendant(task_memcg, memcg);
-       css_put(&task_memcg->css);
-       return ret;
-}
-
 /**
  * mem_cgroup_margin - calculate chargeable space of a memory cgroup
  * @memcg: the memory cgroup

diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index 59326614508a411c591f45a61fa3baee1021705f..b353f468a36aebf1eccc8a036df946c277c260ee 100644 (file)
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -153,17 +153,13 @@ static inline bool is_memcg_oom(struct oom_control *oc)
 
 /* return true if the task is not adequate as candidate victim task. */
 static bool oom_unkillable_task(struct task_struct *p,
-               struct mem_cgroup *memcg, const nodemask_t *nodemask)
+                               const nodemask_t *nodemask)
 {
        if (is_global_init(p))
                return true;
        if (p->flags & PF_KTHREAD)
                return true;
 
-       /* When mem_cgroup_out_of_memory() and p is not member of the group */
-       if (memcg && !task_in_mem_cgroup(p, memcg))
-               return true;
-
        /* p may not have freeable memory in nodemask */
        if (!has_intersects_mems_allowed(p, nodemask))
                return true;
@@ -194,20 +190,19 @@ static bool is_dump_unreclaim_slabs(void)
  * oom_badness - heuristic function to determine which candidate task to kill
  * @p: task struct of which task we should calculate
  * @totalpages: total present RAM allowed for page allocation
- * @memcg: task's memory controller, if constrained
  * @nodemask: nodemask passed to page allocator for mempolicy ooms
  *
  * The heuristic for determining which task to kill is made to be as simple and
  * predictable as possible.  The goal is to return the highest value for the
  * task consuming the most memory to avoid subsequent oom failures.
  */
-unsigned long oom_badness(struct task_struct *p, struct mem_cgroup *memcg,
+unsigned long oom_badness(struct task_struct *p,
                          const nodemask_t *nodemask, unsigned long totalpages)
 {
        long points;
        long adj;
 
-       if (oom_unkillable_task(p, memcg, nodemask))
+       if (oom_unkillable_task(p, nodemask))
                return 0;
 
        p = find_lock_task_mm(p);
@@ -318,7 +313,7 @@ static int oom_evaluate_task(struct task_struct *task, void *arg)
        struct oom_control *oc = arg;
        unsigned long points;
 
-       if (oom_unkillable_task(task, NULL, oc->nodemask))
+       if (oom_unkillable_task(task, oc->nodemask))
                goto next;
 
        /*
@@ -342,7 +337,7 @@ static int oom_evaluate_task(struct task_struct *task, void *arg)
                goto select;
        }
 
-       points = oom_badness(task, NULL, oc->nodemask, oc->totalpages);
+       points = oom_badness(task, oc->nodemask, oc->totalpages);
        if (!points || points < oc->chosen_points)
                goto next;
 
@@ -387,7 +382,7 @@ static int dump_task(struct task_struct *p, void *arg)
        struct oom_control *oc = arg;
        struct task_struct *task;
 
-       if (oom_unkillable_task(p, NULL, oc->nodemask))
+       if (oom_unkillable_task(p, oc->nodemask))
                return 0;
 
        task = find_lock_task_mm(p);
@@ -1084,7 +1079,7 @@ bool out_of_memory(struct oom_control *oc)
        check_panic_on_oom(oc);
 
        if (!is_memcg_oom(oc) && sysctl_oom_kill_allocating_task &&
-           current->mm && !oom_unkillable_task(current, NULL, oc->nodemask) &&
+           current->mm && !oom_unkillable_task(current, oc->nodemask) &&
            current->signal->oom_score_adj != OOM_SCORE_ADJ_MIN) {
                get_task_struct(current);
                oc->chosen = current;