Commit 431f42fd authored by Michal Hocko's avatar Michal Hocko Committed by Linus Torvalds

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.czSuggested-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarMichal Hocko <mhocko@suse.com>
Reviewed-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Cc: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent c3b78b11
...@@ -534,8 +534,16 @@ bool __oom_reap_task_mm(struct mm_struct *mm) ...@@ -534,8 +534,16 @@ bool __oom_reap_task_mm(struct mm_struct *mm)
return ret; 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) static bool oom_reap_task_mm(struct task_struct *tsk, struct mm_struct *mm)
{ {
bool ret = true;
if (!down_read_trylock(&mm->mmap_sem)) { if (!down_read_trylock(&mm->mmap_sem)) {
trace_skip_task_reaping(tsk->pid); trace_skip_task_reaping(tsk->pid);
return false; return false;
...@@ -548,28 +556,28 @@ static bool oom_reap_task_mm(struct task_struct *tsk, struct mm_struct *mm) ...@@ -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(). * down_write();up_write() cycle in exit_mmap().
*/ */
if (test_bit(MMF_OOM_SKIP, &mm->flags)) { if (test_bit(MMF_OOM_SKIP, &mm->flags)) {
up_read(&mm->mmap_sem);
trace_skip_task_reaping(tsk->pid); trace_skip_task_reaping(tsk->pid);
return true; goto out_unlock;
} }
trace_start_task_reaping(tsk->pid); trace_start_task_reaping(tsk->pid);
/* failed to reap part of the address space. Try again later */ /* failed to reap part of the address space. Try again later */
if (!__oom_reap_task_mm(mm)) { ret = __oom_reap_task_mm(mm);
up_read(&mm->mmap_sem); if (!ret)
return false; goto out_finish;
}
pr_info("oom_reaper: reaped process %d (%s), now anon-rss:%lukB, file-rss:%lukB, shmem-rss:%lukB\n", 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, task_pid_nr(tsk), tsk->comm,
K(get_mm_counter(mm, MM_ANONPAGES)), K(get_mm_counter(mm, MM_ANONPAGES)),
K(get_mm_counter(mm, MM_FILEPAGES)), K(get_mm_counter(mm, MM_FILEPAGES)),
K(get_mm_counter(mm, MM_SHMEMPAGES))); K(get_mm_counter(mm, MM_SHMEMPAGES)));
out_finish:
trace_finish_task_reaping(tsk->pid);
out_unlock:
up_read(&mm->mmap_sem); up_read(&mm->mmap_sem);
trace_finish_task_reaping(tsk->pid); return ret;
return true;
} }
#define MAX_OOM_REAP_RETRIES 10 #define MAX_OOM_REAP_RETRIES 10
......
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