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Wed, 11 Nov 2026 14:25:28 -0500 (EST) Date: Wed, 11 Nov 2026 19:25:27 +0000 From: Kiryl Shutsemau To: Tal Zussman Cc: Andrew Morton , Mike Rapoport , Peter Xu , James Houghton , Andrea Arcangeli , Suren Baghdasaryan , Balbir Singh , "Liam R. Howlett" , Lorenzo Stoakes , Vlastimil Babka , Jann Horn , Pedro Falcato , =?utf-8?B?TWljaGHFgiBNaXJvc8WCYXc=?= , Andrei Vagin , Stephen Rothwell , Arnd Bergmann , Muhammad Usama Anjum , David Hildenbrand , Zi Yan , Matthew Brost , Joshua Hahn , Byungchul Park , Gregory Price , Ying Huang , Alistair Popple , Baolin Wang , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Usama Arif , Chris Down , Muchun Song , Oscar Salvador , =?utf-8?Q?Miko=C5=82aj?= Lenczewski , Michal Hocko , Mike Kravetz , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org Subject: Re: [PATCH 11/12] mm/madvise: send UFFD_EVENT_REMOVE when installing guard regions Message-ID: References: <20261111-uffd-state-fixes-v1-0-00713d368976@columbia.edu> <20261111-uffd-state-fixes-v1-11-00713d368976@columbia.edu> X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20261111-uffd-state-fixes-v1-11-00713d368976@columbia.edu> X-Stat-Signature: qbfnayax9zw33wxgz3dcjkwo1gm9wfae X-Rspamd-Server: rspam01 X-Rspam-User: X-Spam-Status: No, score=-5.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_PASS,SPF_PASS autolearn=no autolearn_force=no version=4.0.1 X-Rspamd-Queue-Id: 51212140007 X-HE-Tag: 1794425141-570377 X-HE-Meta: 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 9tK0GEbK VNGlM75eoCaU6yqBJObGvn8i11mG0HnmjljVohFhWgrLR28hQnYv6IkO9gTVkJEbhFnIIqkncVHXVTNGztgY+W0r2bKFoUt5GzRPYfkAAbogf0sD/4qRPKrENpQa5xFyjxymRbOb51jbusukXuwCRQUr4PUR/9sWsyfKsv0xaVsBxxoXpab1rqjowN8go3zx5QA+QLg2xDPVmXQH6X707TLfY6oDIOpxS7dZhErqT7dj6ZiaT9DAgbnuN9FQCwNGBZj4oq/z0MslZQ6dEkzafVxjo1AL1W6MMVAI7bCB1y3BUA2kde0ZHG9XB4xBfSW7+MArXPo6g5lxnI0Nkjzel7sBpFnbgOWIqevSZwhZOdjH7vTmUVW20Wgo+/wfzYlwDKuIloWbEtiMJm1JMhQuO6yfhMygW7zGnuERcnunh4FYY00k= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 On Wed, Nov 11, 2026 at 12:55:19PM -0500, Tal Zussman wrote: > On an anonymous VMA, the zap drops uffd-wp and RWP protection along with > the pages. Writes and accesses to the range after the guard is removed > are then not reported, and the manager cannot know that it has to > protect the range again. For RWP this only holds if the range is registered without MISSING. The zap frees the pages, so with MISSING the first access after the guard is removed is reported as a missing fault. And there is nothing to protect again: RWP only covers present PTEs, and a page faulted back in shows up as accessed in PAGEMAP_SCAN. -- Kiryl Shutsemau / Kirill A. Shutemov