linux-kernel - Re: [PATCH 03/13] mm/munlock: delete munlock_vma_pages

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Date:   Thu, 10 Feb 2022 16:30:32 +0100
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Hugh Dickins <hughd@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     Michal Hocko <mhocko@...e.com>,
        "Kirill A. Shutemov" <kirill@...temov.name>,
        Matthew Wilcox <willy@...radead.org>,
        David Hildenbrand <david@...hat.com>,
        Alistair Popple <apopple@...dia.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Rik van Riel <riel@...riel.com>,
        Suren Baghdasaryan <surenb@...gle.com>,
        Yu Zhao <yuzhao@...gle.com>, Greg Thelen <gthelen@...gle.com>,
        Shakeel Butt <shakeelb@...gle.com>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH 03/13] mm/munlock: delete munlock_vma_pages_all(), allow
 oomreap

On 2/6/22 22:34, Hugh Dickins wrote:
> munlock_vma_pages_range() will still be required, when munlocking but
> not munmapping a set of pages; but when unmapping a pte, the mlock count
> will be maintained in much the same way as it will be maintained when
> mapping in the pte.  Which removes the need for munlock_vma_pages_all()
> on mlocked vmas when munmapping or exiting: eliminating the catastrophic
> contention on i_mmap_rwsem, and the need for page lock on the pages.
> 
> There is still a need to update locked_vm accounting according to the
> munmapped vmas when munmapping: do that in detach_vmas_to_be_unmapped().
> exit_mmap() does not need locked_vm updates, so delete unlock_range().
> 
> And wasn't I the one who forbade the OOM reaper to attack mlocked vmas,
> because of the uncertainty in blocking on all those page locks?
> No fear of that now, so permit the OOM reaper on mlocked vmas.
> 
> Signed-off-by: Hugh Dickins <hughd@...gle.com>

Acked-by: Vlastimil Babka <vbabka@...e.cz>