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Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Jann Horn , Pedro Falcato , "Matthew Wilcox (Oracle)" , Jan Kara , Miaohe Lin , Naoya Horiguchi , Rik van Riel , Harry Yoo , Lance Yang , Kees Cook , Zi Yan , Baolin Wang , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Usama Arif , Matthew Brost , Joshua Hahn , Rakie Kim , Byungchul Park , Gregory Price , Ying Huang , Alistair Popple , Peter Xu , Xu Xin , Chengming Zhou , Arnd Bergmann , Greg Kroah-Hartman , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kselftest@vger.kernel.org Subject: Re: [PATCH v2 00/15] mm/rmap: index MAP_PRIVATE file-backed folios by virt pgoff Message-Id: <20260720124812.30e04cc81a56dd6f0346cdf6@linux-foundation.org> In-Reply-To: <20260720-b4-scalable-cow-virt-pgoff-v2-0-2d549757a76f@kernel.org> References: <20260720-b4-scalable-cow-virt-pgoff-v2-0-2d549757a76f@kernel.org> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 97A1D20005 X-Rspam-User: X-Stat-Signature: ym6prumwdd13w4u1sjjx45wt3q3rzomq X-Rspamd-Server: rspam04 X-HE-Tag: 1784576895-391408 X-HE-Meta: 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 BaOBAYDm BxJyeHmhht0Fg+MLRwJPWwZnXY9fQPnuXW94WK7tkVzI0bcRhLXLZt3v+wWXdooNcWjOxSrC7ojLKSfXNdKbHPCAIwCkDvDB0zbtWi11bl5k9eUqOqqz6QF5xCJjTpCy15+mfaVyWa/axzLFqN0lLMXZuJjdn9NYbtplKAxPI4f6vv7NaRCAWHpd54mAnrvfRCsaYfNXHocycyUJ22G5fAVmLQqYpuAzF+QF1CKX3PexjjHn5ChaS2XjXuaFri3hCoZ4GPekrbi64+3p3dv+XRqPcmqvHYWMv1SjujDlYmMXEG4oN/JJ1rI1w4Y/LDkuE6wQB0zUnGIaDLRNwxzw5wG23xK6qq+ZLuByLPApgi4iHwPlPLj7JbJ/aGvtefpwQtbXROBDpxmbW4/0Vi7E0gJjYCE5iwcTLcHdgTLz22axiiyO4bxJgUotgixJibFmraP1rH0ZPKYPnREk= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, 20 Jul 2026 15:38:26 +0100 "Lorenzo Stoakes (ARM)" wrote: > In memory management we've managed to manufacture a great deal of confusion > around the concept of anonymous memory. We have: > > 1. 'Pure anon' memory - anonymous VMAs whose folios are anonymous and > swap-backed (thus for reclaim purposes, treated as anonymous). These are > simple enough. > > 2. shmem - file-backed VMAs, file-backed folios (from rmap perspective) so > present in the page cache and mapped by an address_space object, but > whose folios are also swap-backed (thus treated as anonymous for reclaim > purposes). > > 3. MAP_PRIVATE-mapped /dev/zero - a strange beast whose VMAs have > vma->vm_file set, but whose mmap_prepare callback clears vma->vm_ops to > satisfy vma_is_anonymous(), which results in VMAs that were mmap()'d > referencing a file, but are in every other sense anonymous, including the > folios. > > 4. Other MAP_PRIVATE-file backed mappings - These possess file-backed VMAs > and have file-backed folios until CoW'd, at which point those CoW'd > folios are anonymous. > > This series fixes issues 3 and 4. Thanks, I'll add this to mm-new for review-n-test. AI review seems overloaded at present, might have found a few things: https://sashiko.dev/#/patchset/20260720-b4-scalable-cow-virt-pgoff-v2-0-2d549757a76f@kernel.org