Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Subject: Re: [PATCH v5 2/3] Revert "mremap: don't allow MREMAP_DONTUNMAP on
 special_mappings and aio"
To:     Brian Geffon <bgeffon@google.com>,
        Andrew Morton <akpm@linux-foundation.org>
Cc:     Axel Rasmussen <axelrasmussen@google.com>,
        Lokesh Gidra <lokeshgidra@google.com>,
        Mike Rapoport <rppt@linux.vnet.ibm.com>,
        Peter Xu <peterx@redhat.com>, Hugh Dickins <hughd@google.com>,
        "Michael S . Tsirkin" <mst@redhat.com>,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        Andy Lutomirski <luto@amacapital.net>,
        Vlastimil Babka <vbabka@suse.cz>,
        Andrea Arcangeli <aarcange@redhat.com>,
        Sonny Rao <sonnyrao@google.com>,
        Minchan Kim <minchan@kernel.org>,
        "Kirill A . Shutemov" <kirill@shutemov.name>,
        Dmitry Safonov <dima@arista.com>,
        Michael Kerrisk <mtk.manpages@gmail.com>,
        Alejandro Colomar <alx.manpages@gmail.com>
References: <20210303175235.3308220-1-bgeffon@google.com>
 <20210323182520.2712101-1-bgeffon@google.com>
 <20210323182520.2712101-2-bgeffon@google.com>
From:   Dmitry Safonov <0x7f454c46@gmail.com>
Message-ID: <558d3b1d-b783-5368-8600-40568c434dcf@gmail.com>
Date:   Tue, 23 Mar 2021 19:05:05 +0000
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101
 Thunderbird/78.8.1
MIME-Version: 1.0
In-Reply-To: <20210323182520.2712101-2-bgeffon@google.com>
Content-Type: text/plain; charset=utf-8
Content-Language: en-US
Content-Transfer-Encoding: 7bit
Precedence: bulk

On 3/23/21 6:25 PM, Brian Geffon wrote:
> This reverts commit cd544fd1dc9293c6702fab6effa63dac1cc67e99.
> 
> As discussed in [1] this commit was a no-op because the mapping type was
> checked in vma_to_resize before move_vma is ever called. This meant that
> vm_ops->mremap() would never be called on such mappings. Furthermore,
> we've since expanded support of MREMAP_DONTUNMAP to non-anonymous
> mappings, and these special mappings are still protected by the existing
> check of !VM_DONTEXPAND and !VM_PFNMAP which will result in a -EINVAL.
> 
> 1. https://lkml.org/lkml/2020/12/28/2340
> 
> Signed-off-by: Brian Geffon <bgeffon@google.com>
> Acked-by: Hugh Dickins <hughd@google.com>

Reviewed-by: Dmitry Safonov <0x7f454c46@gmail.com>

Thanks,
Dmitry