linux-kernel - Re: [PATCH v4 1/2] mm: introduce process

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <CAJuCfpFX4t_SpWs5de=dSvW8jWvJ6tYJPFeesY2mYuGtxSDOxg@mail.gmail.com>
Date:   Wed, 4 Aug 2021 09:54:12 -0700
From:   Suren Baghdasaryan <surenb@...gle.com>
To:     Michal Hocko <mhocko@...e.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        David Rientjes <rientjes@...gle.com>,
        Matthew Wilcox <willy@...radead.org>,
        Johannes Weiner <hannes@...xchg.org>,
        Roman Gushchin <guro@...com>, Rik van Riel <riel@...riel.com>,
        Minchan Kim <minchan@...nel.org>,
        Christian Brauner <christian@...uner.io>,
        Christoph Hellwig <hch@...radead.org>,
        Oleg Nesterov <oleg@...hat.com>,
        David Hildenbrand <david@...hat.com>,
        Jann Horn <jannh@...gle.com>,
        Shakeel Butt <shakeelb@...gle.com>,
        Andy Lutomirski <luto@...nel.org>,
        Christian Brauner <christian.brauner@...ntu.com>,
        Florian Weimer <fweimer@...hat.com>,
        Jan Engelhardt <jengelh@...i.de>,
        Tim Murray <timmurray@...gle.com>,
        Linux API <linux-api@...r.kernel.org>,
        linux-mm <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>,
        kernel-team <kernel-team@...roid.com>
Subject: Re: [PATCH v4 1/2] mm: introduce process_mrelease system call

On Tue, Aug 3, 2021 at 11:21 PM Michal Hocko <mhocko@...e.com> wrote:
>
> On Tue 03-08-21 15:09:43, Suren Baghdasaryan wrote:
> > On Tue, Aug 3, 2021 at 10:27 AM Suren Baghdasaryan <surenb@...gle.com> wrote:
> [...]
> > > > > +     if (task_will_free_mem(task) && (task->flags & PF_KTHREAD) == 0) {
> > > > > +             mm = task->mm;
> > > > > +             mmget(mm);
> > > > > +     }
> > > > > +     task_unlock(task);
> > > > > +     if (!mm) {
> > > >
> > > > Do we want to treat MMF_OOM_SKIP as a failure?
> > >
> > > Yeah, I don't think we want to create additional contention if
> > > oom-killer is already working on this mm. Should we return EBUSY in
> > > this case? Other possible options is ESRCH, indicating that this
> > > process is a goner, so don't bother. WDYT?
> >
> > After considering this some more I think ESRCH would be more
> > appropriate. EBUSY might be understood as "I need to retry at a better
> > time", which is not what we want here.
>
> Why cannot we simply return 0 in that case. The work has been done
> already by the kernel so why should we tell the caller that there was
> something wrong?

Ah, you are right. I was under the impression that MMF_OOM_SKIP means
oom-killer is reaping the mm, but looks like it means that mm was
already reaped. If that's true then I agree, returning 0 is the right
move here. Will fix.

>
> --
> Michal Hocko
> SUSE Labs