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([2a02:8084:e84:2480:228:f8ff:fe6f:83a8]) by smtp.gmail.com with ESMTPSA id w6sm23880473wrl.49.2021.03.23.12.05.06 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 23 Mar 2021 12:05:07 -0700 (PDT) Subject: Re: [PATCH v5 2/3] Revert "mremap: don't allow MREMAP_DONTUNMAP on special_mappings and aio" To: Brian Geffon , Andrew Morton Cc: Axel Rasmussen , Lokesh Gidra , Mike Rapoport , Peter Xu , Hugh Dickins , "Michael S . Tsirkin" , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Andy Lutomirski , Vlastimil Babka , Andrea Arcangeli , Sonny Rao , Minchan Kim , "Kirill A . Shutemov" , Dmitry Safonov , Michael Kerrisk , Alejandro Colomar 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 List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 > Acked-by: Hugh Dickins Reviewed-by: Dmitry Safonov <0x7f454c46@gmail.com> Thanks, Dmitry