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Fri, 06 Nov 2026 02:53:48 +0000 X-Mizu-Trace-ID: ea04818497cd00a3 X-Migadu-Flow: FLOW_OUT From: Lance Yang To: david@kernel.org Cc: akpm@linux-foundation.org, ziy@nvidia.com, baolin.wang@linux.alibaba.com, hughd@google.com, liam@infradead.org, nico.pache@linux.dev, ryan.roberts@arm.com, dev.jain@arm.com, baohua@kernel.org, lance.yang@linux.dev, usama.arif@linux.dev, kas@kernel.org, zokeefe@google.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, mason@kernel.org, stable@vger.kernel.org Subject: Re: [PATCH] mm/khugepaged: don't map folios that are not uptodate in MADV_COLLAPSE Date: Fri, 6 Nov 2026 10:53:42 +0800 Message-ID: <20261106025342.18229-1-lance.yang@linux.dev> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20261105-set_huge_pmd_uptodate-v1-1-a78d8a1b7117@kernel.org> References: <20261105-set_huge_pmd_uptodate-v1-1-a78d8a1b7117@kernel.org> X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: E4DFBC0003 X-Spam-Status: No, score=-13.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,MAILING_LIST_MULTI,SPF_HELO_PASS,SPF_PASS, USER_AGENT_GIT autolearn=ham autolearn_force=no version=4.0.1 X-Stat-Signature: jbu6aztbxdtucwd56ihhopzhdgof4hps X-HE-Tag: 1793933629-894849 X-HE-Meta: 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 AnoGUVAR rx68R6HJY2I9bnJ2VEN2X1YStUTFZgJyRlT4YcIdrEPqR8cD0i4x16RNwar/2nzcNnKrZU0IGFGHiDl1yDOjkRD0mmGfJxBWEg956G9gNXY7esaPNe6Xqj28U+LqCrPMcPfUqhZXes/3B3hmgLUIjEKvdsuC/C3WDuqJ47cocTSVH2uS1p4gEGtU2rgeJLJie8LHZbFXFqfPXGlfTZxSclvVTPpWAFzduskOygcQJZjBmjIAH7LBZpJT7lm6Es6zw4A7jZxHgC04iD37hWZh7yYdNO/CbaUzbAQHXEUUj1+KBzPzPqrthjAB/qQ== 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 Thu, Nov 05, 2026 at 07:16:44PM +0100, David Hildenbrand (Arm) wrote: >madvise(MADV_COLLAPSE) can map PMD-sized pagecache folios that are not >uptodate. For example, shmem fallocate() can put such folios into the >page cache. > >collapse_file() already refuses to proceed with folios that are not >uptodate. Let's just do the same in try_collapse_pte_mapped_thp() and skip >such folios, leaving handling to the page faults. > >Note that collapse_file() effectively clears shmem folios through >shmem_get_folio(); let's keep this fix simple and simply let the page >fault path deal with that. > >Fixes: 34488399fa08 ("mm/madvise: add file and shmem support to MADV_COLLAPSE") >Reported-by: Chris Mason >Cc: stable@vger.kernel.org >Signed-off-by: David Hildenbrand (Arm) >--- Nice work1 Reviewed-by: Lance Yang