Received-SPF: softfail (google.com: domain of transitioning linux-kernel-owner@vger.kernel.org does not designate 23.128.96.19 as permitted sender) client-ip=23.128.96.19;
Date:   Wed, 2 Mar 2022 15:24:59 +0100
From:   Michal Hocko <mhocko@suse.com>
To:     Nico Pache <npache@redhat.com>
Cc:     Waiman Long <longman@redhat.com>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, akpm@linux-foundation.org,
        jsavitz@redhat.com, peterz@infradead.org, tglx@linutronix.de,
        mingo@redhat.com, dvhart@infradead.org, dave@stgolabs.net,
        andrealmeid@collabora.com
Subject: Re: [PATCH v3] mm/oom: do not oom reap task with an unresolved
 robust futex
Message-ID: <Yh9+O/xqNLnV1jmA@dhcp22.suse.cz>
References: <20220114180135.83308-1-npache@redhat.com>
 <YeUuWcNArnDhOjFY@dhcp22.suse.cz>
 <ad639326-bea8-9bfb-23e3-4e2b216d9645@redhat.com>
 <43a6c470-9fc2-6195-9a25-5321d17540e5@redhat.com>
 <YeZ/mL808DpA8mdG@dhcp22.suse.cz>
 <118fc685-c68d-614f-006a-7d5487302122@redhat.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <118fc685-c68d-614f-006a-7d5487302122@redhat.com>
Precedence: bulk

Sorry, this has slipped through cracks.

On Mon 14-02-22 15:39:31, Nico Pache wrote:
[...]
> We've recently been discussing the following if statement in __oom_reap_task_mm:
> 	if (vma_is_anonymous(vma) || !(vma->vm_flags & VM_SHARED))
> 
> Given the comment above it, and some of the upstream discussion the original
> RFC, we are struggling to see why this should be a `||` and not an `&&`. If we
> only want to reap anon memory and reaping shared memory can be dangerous is this
> statement incorrect?
> 
> We have a patch queued up to make this change, but wanted to get your opinion on
> why this was originally designed this way in case we are missing something.

I do not really see why this would be wrong. Private file backed
mappings can contain a reapable memory as well. I do not see how this
would solve the futex issue.
-- 
Michal Hocko
SUSE Labs