oom_reaper: avoid pointless atomic_inc_not_zero usage.

Since commit 36324a990cf5 ("oom: clear TIF_MEMDIE after oom_reaper
managed to unmap the address space") changed to use find_lock_task_mm()
for finding a mm_struct to reap, it is guaranteed that mm->mm_users > 0
because find_lock_task_mm() returns a task_struct with ->mm != NULL.
Therefore, we can safely use atomic_inc().

Link: http://lkml.kernel.org/r/1465024759-8074-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index be67df3..ddf7448 100644 (file)
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -474,14 +474,8 @@ static bool __oom_reap_task(struct task_struct *tsk)
        p = find_lock_task_mm(tsk);
        if (!p)
                goto unlock_oom;
-
        mm = p->mm;
-       if (!atomic_inc_not_zero(&mm->mm_users)) {
-               task_unlock(p);
-               mm = NULL;
-               goto unlock_oom;
-       }
-
+       atomic_inc(&mm->mm_users);
        task_unlock(p);
 
        if (!down_read_trylock(&mm->mmap_sem)) {