[merged mm-stable] mm-huge_memory-skip-zone-device-folios-in-madvise_free_huge_pmd.patch removed from -mm tree

[merged mm-stable] mm-huge_memory-skip-zone-device-folios-in-madvise_free_huge_pmd.patch removed from -mm tree

[Andrew Morton]

The quilt patch titled
     Subject: mm/huge_memory: skip zone device folios in madvise_free_huge_pmd()
has been removed from the -mm tree.  Its filename was
     mm-huge_memory-skip-zone-device-folios-in-madvise_free_huge_pmd.patch

This patch was dropped because it was merged into the mm-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

------------------------------------------------------
From: Gregory Price <gourry@gourry.net>
Subject: mm/huge_memory: skip zone device folios in madvise_free_huge_pmd()
Date: Mon, 17 Aug 2026 18:08:08 -0400

Patch series "mm: reject zone device folios in more folio walkers", v2.

Several LRU-oriented mm walkers resolve the folio backing a PMD entry (or
a physical pfn) and then reclaim, age, migrate, or lazyfree it without
ever checking for ZONE_DEVICE memory.

This series adds missing folio_is_zone_device() rejections, matching the
checks that comparable walkers already perform.

- mm/huge_memory, mm/madvise: the !pmd_present branch above these sites
  only filters device-private entries (which are non-present).

  A present zone device PMD (e.g. device-coherent) would still reach the
  folio and be lazyfreed / aged / paged out. Add an explicit check.

- mm/mempolicy: queue_folios_pmd() can see a present zone device PMD
  (e.g. device-coherent) and queue it for migration.

No crash reproducer - this is a correctness/hardening cleanup found by
inspection.  All checks are placed after the folio is resolved and before
it is acted upon, on paths that already hold the relevant page-table lock,
so no locking or refcount changes are involved.


This patch (of 3):

madvise_free_huge_pmd() resolves the folio backing a PMD via pmd_folio()
and marks it lazyfree without checking for zone device memory.

The surrounding guards do not cover every zone device case:

 - MADV_FREE only operates on anonymous VMAs (DAX mappings are excluded)

 - !pmd_present() branch rejects device-private and migration entries

 - present zone device PMD (device coherent THP) is not filtered.
   Unlike vm_normal_page_pmd(), it performs no special/pfnmap check,
   and would be marked lazyfree here.

Bail out when the folio is a zone device folio.

Link: https://lore.kernel.org/20260817220810.1175596-1-gourry@gourry.net
Link: https://lore.kernel.org/20260817220810.1175596-2-gourry@gourry.net
Fixes: a30b48bf1b24 ("mm/migrate_device: implement THP migration of zone device pages")
Signed-off-by: Gregory Price (Meta) <gourry@gourry.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Reviewed-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>
Tested-by: Lance Yang <lance.yang@linux.dev>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Balbir Singh <balbirs@nvidia.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Byungchul Park <byungchul@sk.com>
Cc: Dev Jain <dev.jain@arm.com>
Cc: "Huang, Ying" <ying.huang@linux.alibaba.com>
Cc: Jann Horn <jannh@google.com>
Cc: Joshua Hahn <joshua.hahnjy@gmail.com>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Rakie Kim <rakie.kim@sk.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Zi Yan <ziy@nvidia.com>
Cc: <stable@vger.kernel.org>
---

 mm/huge_memory.c |    4 ++++
 1 file changed, 4 insertions(+)

--- a/mm/huge_memory.c~mm-huge_memory-skip-zone-device-folios-in-madvise_free_huge_pmd
+++ a/mm/huge_memory.c
@@ -2423,6 +2423,10 @@ bool madvise_free_huge_pmd(struct mmu_ga
 	}
 
 	folio = pmd_folio(orig_pmd);
+
+	if (folio_is_zone_device(folio))
+		goto out;
+
 	/*
 	 * If other processes are mapping this folio, we couldn't discard
 	 * the folio unless they all do MADV_FREE so let's skip the folio.
_

Patches currently in -mm which might be from gourry@gourry.net are

mm-memory_hotplug-factor-out-node_is_memoryless.patch
mm-mempolicy-use-vm_normal_folio_pmd-in-queue_folios_pmd.patch
mm-madvise-use-vm_normal_folio_pmd-in-cold-pageout-pmd-range.patch
mm-refactor-find_next_best_node-to-find_next_best_node_in.patch
mm-page_alloc-refactor-build_node_zonelist-out-of-build_zonelists.patch
proc-task_mmu-handle-special-pmds-in-clear_refs-and-pagemap.patch
mm-madvise-reclaim-isolated-folios-if-pte-restart-fails.patch
mm-madvise-use-folio_trylock-in-the-cold-pageout-pmd-split.patch