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From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
To: mhocko@kernel.org
Cc: guro@fb.com, hannes@cmpxchg.org, vdavydov.dev@gmail.com,
	kernel-team@fb.com, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mm,oom: fix oom invocation issues
Date: Thu, 18 May 2017 22:57:10 +0900	[thread overview]
Message-ID: <201705182257.HJJ52185.OQStFLFMHVOJOF@I-love.SAKURA.ne.jp> (raw)
In-Reply-To: <20170518090039.GC25462@dhcp22.suse.cz>

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().

WARNING: multiple messages have this Message-ID
From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
To: mhocko@kernel.org
Cc: guro@fb.com, hannes@cmpxchg.org, vdavydov.dev@gmail.com,
	kernel-team@fb.com, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mm,oom: fix oom invocation issues
Date: Thu, 18 May 2017 22:57:10 +0900	[thread overview]
Message-ID: <201705182257.HJJ52185.OQStFLFMHVOJOF@I-love.SAKURA.ne.jp> (raw)
In-Reply-To: <20170518090039.GC25462@dhcp22.suse.cz>

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().

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  parent reply	other threads:[~2017-05-18 13:57 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-05-17 15:26 Roman Gushchin
2017-05-17 15:26 ` Roman Gushchin
2017-05-17 16:14 ` Michal Hocko
2017-05-17 16:14   ` Michal Hocko
2017-05-17 19:43   ` Roman Gushchin
2017-05-17 19:43     ` Roman Gushchin
2017-05-17 22:03     ` Tetsuo Handa
2017-05-17 22:03       ` Tetsuo Handa
2017-05-18  8:47       ` Michal Hocko
2017-05-18  8:47         ` Michal Hocko
2017-05-18  9:00         ` Michal Hocko
2017-05-18  9:00           ` Michal Hocko
2017-05-18 13:20           ` Roman Gushchin
2017-05-18 13:20             ` Roman Gushchin
2017-05-18 13:57           ` Tetsuo Handa [this message]
2017-05-18 13:57             ` Tetsuo Handa
2017-05-18 14:29             ` Michal Hocko
2017-05-18 14:29               ` Michal Hocko
2017-05-18 14:57               ` Tetsuo Handa
2017-05-18 14:57                 ` Tetsuo Handa
2017-05-18 15:07                 ` Michal Hocko
2017-05-18 15:07                   ` Michal Hocko
2017-05-18 15:01               ` Michal Hocko
2017-05-18 15:01                 ` Michal Hocko
2017-05-18  8:01     ` Michal Hocko
2017-05-18  8:01       ` Michal Hocko

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