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Tue, 15 Sep 2026 06:46:00 -0400 (EDT) Date: Tue, 15 Sep 2026 11:46:00 +0100 From: Kiryl Shutsemau To: "David Hildenbrand (Arm)" Cc: akpm@linux-foundation.org, ljs@kernel.org, nico.pache@linux.dev, baolin.wang@linux.alibaba.com, baohua@kernel.org, dev.jain@arm.com, hughd@google.com, lance.yang@linux.dev, liam@infradead.org, mhocko@suse.com, rppt@kernel.org, ryan.roberts@arm.com, shuah@kernel.org, surenb@google.com, usama.arif@linux.dev, vbabka@kernel.org, ziy@nvidia.com, usama.anjum@arm.com, agordeev@linux.ibm.com, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, jannh@google.com, willy@infradead.org, pfalcato@suse.de, rostedt@goodmis.org, mhiramat@kernel.org, linux-trace-kernel@vger.kernel.org, bpf@vger.kernel.org Subject: Re: [RFC PATCH 00/57] mm/collapse: rebuild collapse on migration primitives Message-ID: References: <20260816224609.308019-1-kirill@shutemov.name> <9f51ac27-24b2-495b-b397-84865f977d24@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: F098B8000B X-Stat-Signature: 3jndt7yzcw8phtd8w195rwbozdgu9hy4 X-HE-Tag: 1789469164-326446 X-HE-Meta: U2FsdGVkX1+fC3sJksPdwfJDA2fLWHQhHhoEfa0KnZKKHIQMbzcK32TW4KEVdMI4ZXD3J/T8nz7oLXDuHeo7Hd4YPI2WGj5hRYv3x/vOk2I8JZ9jwVFtjzsMzSA7S5KFxfTsilnWuFfGbDIIg6zuGKE2LiY1xu2pC7TaOoPqd5DFwq6yuXjGq6JdGxpzEUDYp7ELslpIOtttBhjgxQaLWDnBdH4AAg87jffjm6xmbVhMaXjqz9BORXbSWemvDOSziF7Ct+VJx4tsvEqDngsMOpv8IyAk6n/sJXUyJ91AtHtsiUJLhh4DvWADSCvVW8xhA0ycM2QKFTcHzM+boPaE7BNfELR1H/wnjrCRRyYK8GV9kqO7LwIxefQ0lVi9RUppZmeJnjP61upHK78qtGncYvmtC5ZTKGyoZ6zhvk2G4mX66dNxRXM5KeVisnlnZivkzgkou7rfsJJ0sQ1I+6mRthzRcOyKik/WNBLUHaKvRH6ss2SlXgLfDXE27qL9BXP1hY6EQuxVjYpkV0TceiiCSSdLKGQ381W3ITgGBVPMH8OsEklni7VI+wMj1JwKYN9c7qn8dFIEJ22xt4pHiu8pqnmSfQAdEGro75EtduWdPSUiFnVa8IGpMNZ0ncN1YMS64WH325w3+ASIL7DOd9hDs3oDTQlI00UdKVLFBTkWBYhUIUPOgUB8fqqwuBngfI25RPpdfR+Vtf0VbtYGmHRMt0+YC87EqP/OdF8WYp5bZ28aR7jLC1i8UR/ktUT6aWzufRdx5NHN8h0wkLNtcRsx6csNWCC9n4uI7CM4OdMp0MOVw9SXdUSpNFanyWJhFeSVOHhPBszDM6+M15EcR54kWEj2cjHD+rbTuha+OKBmbFqvCz+C0FXy/SrpALff/uHuHmhIvxOr12bbH04zLim1y1eGZEV9QTRQFq6F2WMo6a5931t7Mq1XRMGwvxtn6QPIf6SlDXGeHC2G1peuP3I wFLQc6RR Gv7wi2sTnCmVUXDglkN+8JlcxmIg/3dxfMsAXSisezt26sizB5jX+pc63qWOBrROyWOt26MSrbyzIvWstCq1JXxu0R5qVO2SlcOB4BAvJ527Ze4TJWveVlcmO7CmZYHdTF0ry3kxHnMAvMdrr4e9s8/jsubDsPva2KIpVz5lMUtVg7narhAG7sZCKa/JLWdHg8ooIVCWIoirXa8klXaR+qEaWqjzuIoTW+orOh/oiQeFR8Oj8S8RrqeWIvfEHLraWZF3cM7oOpa2/qfYIGsOIN8Okhf99dNEa1U77wCsw3ZCX3w5V24ii+auu//HYkpZ4Kg6juGW8NHpGboJAvQgAnPLieZdPJtClWATQtK5/O5JhoXjkNJJ1NyLV4M+15DUFEj9JD4nE4a3mUFZX5MiFvsTb39s7mhrhfbKp1+8uEe/eotcjET/6o2Z3b5i6sAC/hhRmPZ+DSedab7R6b0Sl91+hQg== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Sep 14, 2026 at 05:07:37PM +0200, David Hildenbrand (Arm) wrote: > > As I mentioned above, we drop the ptl after the freeze. And take it a > > second time for the install. Allocation and the copy run in between with > > no lock held -- on 64K the copy at PMD order is 512M of it, which is why > > it cannot sit under either lock. > > Hold on, are freezing all folios to collapse? That cannot possibly work with > COW-shared folios that are mapped into other address spaces. I break COW for worthy candidates in the faultin prepass before freeze, alongside swapin. It simplifies the picture substantially. No rmap mess. -- Kiryl Shutsemau / Kirill A. Shutemov