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mm/oom_kill.c: clean up oom_reap_task_mm() 

Andrew has noticed some inconsistencies in oom_reap_task_mm.  Notably

 - Undocumented return value.

 - comment "failed to reap part..." is misleading - sounds like it's
   referring to something which happened in the past, is in fact
   referring to something which might happen in the future.

 - fails to call trace_finish_task_reaping() in one case

 - code duplication.

 - Increases mmap_sem hold time a little by moving
   trace_finish_task_reaping() inside the locked region.  So sue me ;)

 - Sharing the finish: path means that the trace event won't
   distinguish between the two sources of finishing.

Add a short explanation for the return value and fix the rest by
reorganizing the function a bit to have unified function exit paths.

Link: http://lkml.kernel.org/r/20180724141747.GP28386@dhcp22.suse.cz
Suggested-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Michal Hocko 2018-08-21 21:52:45 -07:00 committed by Linus Torvalds
parent c3b78b11ef
commit 431f42fdfd
1 changed files with 16 additions and 8 deletions
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24
mm/oom_kill.c
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@ -534,8 +534,16 @@ bool __oom_reap_task_mm(struct mm_struct *mm)
return ret;
}
/*
* Reaps the address space of the give task.
*
* Returns true on success and false if none or part of the address space
* has been reclaimed and the caller should retry later.
*/
static bool oom_reap_task_mm(struct task_struct *tsk, struct mm_struct *mm)
{
bool ret = true;
if (!down_read_trylock(&mm->mmap_sem)) {
trace_skip_task_reaping(tsk->pid);
return false;
@ -548,28 +556,28 @@ static bool oom_reap_task_mm(struct task_struct *tsk, struct mm_struct *mm)
* down_write();up_write() cycle in exit_mmap().
*/
if (test_bit(MMF_OOM_SKIP, &mm->flags)) {
up_read(&mm->mmap_sem);
trace_skip_task_reaping(tsk->pid);
return true;
goto out_unlock;
}
trace_start_task_reaping(tsk->pid);
/* failed to reap part of the address space. Try again later */
if (!__oom_reap_task_mm(mm)) {
up_read(&mm->mmap_sem);
return false;
}
ret = __oom_reap_task_mm(mm);
if (!ret)
goto out_finish;
pr_info("oom_reaper: reaped process %d (%s), now anon-rss:%lukB, file-rss:%lukB, shmem-rss:%lukB\n",
task_pid_nr(tsk), tsk->comm,
K(get_mm_counter(mm, MM_ANONPAGES)),
K(get_mm_counter(mm, MM_FILEPAGES)),
K(get_mm_counter(mm, MM_SHMEMPAGES)));
out_finish:
trace_finish_task_reaping(tsk->pid);
out_unlock:
up_read(&mm->mmap_sem);
trace_finish_task_reaping(tsk->pid);
return true;
return ret;
}
#define MAX_OOM_REAP_RETRIES 10