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Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Usama Arif , Joshua Hahn , Rakie Kim , Byungchul Park , Gregory Price , Ying Huang , Alistair Popple , Balbir Singh , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , =?UTF-8?q?Thomas=20Hellstr=C3=B6m?= , Francois Dugast , stable@vger.kernel.org Subject: [PATCH v2 1/5] mm/migrate_device: Clear MIGRATE_PFN_MIGRATE on all sub-folios of a split THP Date: Wed, 5 Aug 2026 12:35:32 -0700 Message-Id: <20260805193536.3756457-2-matthew.brost@intel.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20260805193536.3756457-1-matthew.brost@intel.com> References: <20260805193536.3756457-1-matthew.brost@intel.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit migrate_vma_split_unmapped_folio() propagates MIGRATE_PFN_MIGRATE from the head entry to all HPAGE_PMD_NR entries of src_pfns[]. The two bailouts below it in __migrate_device_pages() only cleared the head, and the "next" label then advances by @nr, so the tails keep the flag and a valid destination without ever going through folio_migrate_mapping(). migrate_vma_finalize() then maps unpopulated destination folios into userspace. Clear the flag across the whole @nr range at both bailouts. Reported-by: Sashiko Fixes: 4265d67e405a ("mm/migrate_device: add THP splitting during migration") Cc: Andrew Morton Cc: David Hildenbrand Cc: Lorenzo Stoakes Cc: Zi Yan Cc: Baolin Wang Cc: Liam R. Howlett Cc: Nico Pache Cc: Ryan Roberts Cc: Dev Jain Cc: Barry Song Cc: Lance Yang Cc: Usama Arif Cc: Joshua Hahn Cc: Rakie Kim Cc: Byungchul Park Cc: Gregory Price Cc: Ying Huang Cc: Alistair Popple Cc: Balbir Singh Cc: Maarten Lankhorst Cc: Maxime Ripard Cc: Thomas Zimmermann Cc: David Airlie Cc: Simona Vetter Cc: Thomas Hellström Cc: Francois Dugast Cc: dri-devel@lists.freedesktop.org Cc: linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org Cc: stable@vger.kernel.org Assisted-by: GitHub_Copilot:claude-opus-5 Signed-off-by: Matthew Brost --- mm/migrate_device.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/mm/migrate_device.c b/mm/migrate_device.c index 908d2d4ec43a..d37a96cc6335 100644 --- a/mm/migrate_device.c +++ b/mm/migrate_device.c @@ -1199,10 +1199,14 @@ static void __migrate_device_pages(unsigned long *src_pfns, * device private or coherent memory. * * Try to get rid of swap cache if possible. + * + * @folio may have been split into @nr folios + * above, so clear all of them. */ if (!folio_test_anon(folio) || !folio_free_swap(folio)) { - src_pfns[i] &= ~MIGRATE_PFN_MIGRATE; + for (j = 0; j < nr && i + j < npages; j++) + src_pfns[i+j] &= ~MIGRATE_PFN_MIGRATE; goto next; } } @@ -1210,7 +1214,8 @@ static void __migrate_device_pages(unsigned long *src_pfns, /* * Other types of ZONE_DEVICE page are not supported. */ - src_pfns[i] &= ~MIGRATE_PFN_MIGRATE; + for (j = 0; j < nr && i + j < npages; j++) + src_pfns[i+j] &= ~MIGRATE_PFN_MIGRATE; goto next; } -- 2.34.1