linux-kernel - Re: [PATCH v2 2/3] mm: introduce process

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Message-ID: <472b91d2-d678-2d54-b2d0-8618f32e6e69@redhat.com>
Date:   Thu, 22 Jul 2021 09:45:42 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Suren Baghdasaryan <surenb@...gle.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Michal Hocko <mhocko@...nel.org>,
        Michal Hocko <mhocko@...e.com>,
        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>, 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 v2 2/3] mm: introduce process_mrelease system call

>>> Getting a hold of the mm and locking the mmap_lock would be sufficient I guess.
> 
> That's exactly what I do here. The simplified sequence is:
> 
>         task_lock
>         if (task_will_free_mem())
>                 mm=mmget()
>         task_unlock
>         if (!mm) return;
> 
>         mmap_read_lock(mm)
>         __oom_reap_task_mm(mm)
>         mmap_read_unlock(mm)
>         mmput(mm)
> 
> Or did I misunderstand your comments?

Oh, sorry, my tired eyes confused "put_task_struct()" with 
"task_unlock()" and even "mmget()" with "mmgrab()" ...

So this is essentially get_task_mm() with an additional 
task_will_free_mem() check.

LGHTM!

:)

-- 
Thanks,

David / dhildenb