Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Message-ID: <5363cc40-e4ae-d1fd-9f94-fc61811e70ac@suse.cz>
Date:   Thu, 10 Feb 2022 16:30:32 +0100
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101
 Thunderbird/91.5.1
Subject: Re: [PATCH 03/13] mm/munlock: delete munlock_vma_pages_all(), allow
 oomreap
Content-Language: en-US
To:     Hugh Dickins <hughd@google.com>,
        Andrew Morton <akpm@linux-foundation.org>
Cc:     Michal Hocko <mhocko@suse.com>,
        "Kirill A. Shutemov" <kirill@shutemov.name>,
        Matthew Wilcox <willy@infradead.org>,
        David Hildenbrand <david@redhat.com>,
        Alistair Popple <apopple@nvidia.com>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Rik van Riel <riel@surriel.com>,
        Suren Baghdasaryan <surenb@google.com>,
        Yu Zhao <yuzhao@google.com>, Greg Thelen <gthelen@google.com>,
        Shakeel Butt <shakeelb@google.com>,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org
References: <8e4356d-9622-a7f0-b2c-f116b5f2efea@google.com>
 <8dddb3d4-361-da5-538-3f3ae1b326b@google.com>
From:   Vlastimil Babka <vbabka@suse.cz>
In-Reply-To: <8dddb3d4-361-da5-538-3f3ae1b326b@google.com>
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 7bit
Precedence: bulk

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@google.com>

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