From: Baolin Wang <baolin.wang@linux.alibaba.com>
Date: Fri, 6 Mar 2026 06:43:39 +0000 (+0800)
Subject: mm: rmap: add a ZONE_DEVICE folio warning in folio_referenced()
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=83ec1286b173e6ff54d0dd0291fbc517d65a8d5b;p=thirdparty%2Fkernel%2Flinux.git

mm: rmap: add a ZONE_DEVICE folio warning in folio_referenced()

The folio_referenced() is used to test whether a folio was referenced
during reclaim.  Moreover, ZONE_DEVICE folios are controlled by their
device driver, have a lifetime tied to that driver, and are never placed
on the LRU list.  That means we should never try to reclaim ZONE_DEVICE
folios, so add a warning to catch this unexpected behavior in
folio_referenced() to avoid confusion, as discussed in the previous
thread[1].

[1] https://lore.kernel.org/all/16fb7985-ec0f-4b56-91e7-404c5114f899@kernel.org/
Link: https://lkml.kernel.org/r/64d6fb2a33f7101e1d4aca2c9052e0758b76d492.1772778858.git.baolin.wang@linux.alibaba.com
Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Reviewed-by: Alistair Popple <apopple@nvidia.com>
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dev Jain <dev.jain@arm.com>
Cc: Jann Horn <jannh@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Lorenzo Stoakes (Oracle) <ljs@kernel.org>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Qi Zheng <zhengqi.arch@bytedance.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Wei Xu <weixugc@google.com>
Cc: Will Deacon <will@kernel.org>
Cc: Yuanchu Xie <yuanchu@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

diff --git a/mm/rmap.c b/mm/rmap.c
index 5fd22ba59d355..cd48f34f11b5b 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1072,6 +1072,7 @@ int folio_referenced(struct folio *folio, int is_locked,
 		.invalid_vma = invalid_folio_referenced_vma,
 	};
 
+	VM_WARN_ON_ONCE_FOLIO(folio_is_zone_device(folio), folio);
 	*vm_flags = 0;
 	if (!pra.mapcount)
 		return 0;