Re: [PATCH] mm,oom: fix oom invocation issues

From	Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Newsgroups	linux.kernel
Subject	Re: [PATCH] mm,oom: fix oom invocation issues
Date	2017-05-18 16:00 +0200
Message-ID	<tIu89-3sl-1@gated-at.bofh.it> (permalink)
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Michal Hocko wrote:
> It is racy and it basically doesn't have any allocation context so we
> might kill a task from a different domain. So can we do this instead?
> There is a slight risk that somebody might have returned VM_FAULT_OOM
> without doing an allocation but from my quick look nobody does that
> currently.

I can't tell whether it is safe to remove out_of_memory() from pagefault_out_of_memory().
There are VM_FAULT_OOM users in fs/ directory. What happens if pagefault_out_of_memory()
was called as a result of e.g. GFP_NOFS allocation failure? Is it guaranteed that all
memory allocations that might occur from page fault event (or any action that might return
VM_FAULT_OOM) are allowed to call oom_kill_process() from out_of_memory() before
reaching pagefault_out_of_memory() ?

Anyway, I want

	/* Avoid allocations with no watermarks from looping endlessly */
-	if (test_thread_flag(TIF_MEMDIE))
+	if (alloc_flags == ALLOC_NO_WATERMARKS && test_thread_flag(TIF_MEMDIE))
		goto nopage;

so that we won't see similar backtraces and memory information from both
out_of_memory() and warn_alloc().

Thread

[PATCH] mm,oom: fix oom invocation issues Roman Gushchin <guro@fb.com> - 2017-05-17 17:30 +0200
  Re: [PATCH] mm,oom: fix oom invocation issues Michal Hocko <mhocko@kernel.org> - 2017-05-17 18:20 +0200
    Re: [PATCH] mm,oom: fix oom invocation issues Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> - 2017-05-18 00:10 +0200
      Re: [PATCH] mm,oom: fix oom invocation issues Michal Hocko <mhocko@kernel.org> - 2017-05-18 10:50 +0200
        Re: [PATCH] mm,oom: fix oom invocation issues Michal Hocko <mhocko@kernel.org> - 2017-05-18 11:10 +0200
          Re: [PATCH] mm,oom: fix oom invocation issues Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> - 2017-05-18 16:00 +0200
            Re: [PATCH] mm,oom: fix oom invocation issues Michal Hocko <mhocko@kernel.org> - 2017-05-18 16:30 +0200
              Re: [PATCH] mm,oom: fix oom invocation issues Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> - 2017-05-18 17:00 +0200
                Re: [PATCH] mm,oom: fix oom invocation issues Michal Hocko <mhocko@kernel.org> - 2017-05-18 17:10 +0200
              Re: [PATCH] mm,oom: fix oom invocation issues Michal Hocko <mhocko@kernel.org> - 2017-05-18 17:10 +0200
    Re: [PATCH] mm,oom: fix oom invocation issues Michal Hocko <mhocko@kernel.org> - 2017-05-18 10:10 +0200

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