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Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Hugh Dickins , Chris Mason , linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@meta.com, Sashiko Subject: Re: [PATCH v2 1/2] mm/memory: recheck PG_uptodate after ->page_mkwrite() Message-ID: References: <20261109120403.82361-1-kas@kernel.org> <20261109120403.82361-2-kas@kernel.org> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Mon, Nov 09, 2026 at 08:30:47PM +0000, Matthew Wilcox wrote: > On Mon, Nov 09, 2026 at 12:04:01PM +0000, Kiryl Shutsemau (Meta) wrote: > > do_shared_fault() unlocks the folio around ->page_mkwrite(). Writeback > > can lock it in that window, fail, and clear PG_uptodate with the folio > > left in the page cache. ecryptfs_writepages() does this when encryption > > fails. filemap_page_mkwrite() relocks the folio and checks only > > ->mapping, so the fault maps a folio that is not uptodate: > > Filesystems that do this are buggy. They shuld be fixed, not worked > around like this. Fair. What is your take on the way out? Is there a timeline for the filesystem fixes? Until they land, mm should still not map a folio that is not uptodate. Would WARN_ON_ONCE() and SIGBUS, like the other checks in 2/2, work for you? It flags the buggy filesystem instead of hiding it. -- Kiryl Shutsemau / Kirill A. Shutemov