From 8ee1ef0f2f8ce29338f4ab00a3d344c010208058 Mon Sep 17 00:00:00 2001 From: Wupeng Ma Date: Tue, 7 Jul 2026 19:02:54 +0800 Subject: mm/hugetlb: fix missing migratable flag on same-node hugetlb migration Commit ba23f58de896 ("mm/migrate: don't call folio_putback_active_hugetlb() on dst hugetlb folio") moved setting of the migratable flag and active-list placement from folio_putback_active_hugetlb(dst) into move_hugetlb_state(), so that the freshly allocated destination folio is handled where allocation is known to have succeeded. Unfortunately, the new code was appended after the existing temporary-folio block in move_hugetlb_state(), which contains an early return added earlier by commit 5af1ab1d24e08 ("mm/hugetlb: optimize the surplus state transfer code in move_hugetlb_state()"): if (folio_test_hugetlb_temporary(new_folio)) { ... if (new_nid == old_nid) return; <-- skips the new code ... } /* added by ba23f58 */ folio_set_hugetlb_migratable(new_folio); list_move_tail(&new_folio->lru, ...&h->hugepage_activelist); When the destination folio is temporary (i.e. the hugetlb pool was exhausted and the migration callback fell back to alloc_migrate_hugetlb_folio()) and the migration does not cross a node -- the common case, and always true on a single-NUMA system -- move_hugetlb_state() returns before setting the migratable flag or adding the new folio to the active list. The destination folio is then installed in the page table but cannot be isolated afterwards, since folio_isolate_hugetlb() rejects folios without the migratable flag; a subsequent soft-offline, hard-offline or memory-hotplug offline of that folio fails with -EBUSY. This was reproduced on a single-NUMA arm64 VM: a second MADV_SOFT_OFFLINE on an already-migrated hugetlb page returned EBUSY and logged "hugepage isolation failed". Keep the surplus adjustment, which is the only part that depends on the node crossing, guarded by `if (new_nid != old_nid)', while making the migratable flag and active-list placement unconditional. This preserves the cleanup intent of ba23f58 and closes the early-return hole. Link: https://lore.kernel.org/20260707110254.3147686-1-mawupeng1@huawei.com Fixes: ba23f58de896 ("mm/migrate: don't call folio_putback_active_hugetlb() on dst hugetlb folio") Signed-off-by: Wupeng Ma Acked-by: David Hildenbrand (Arm) Cc: Baolin Wang Cc: Muchun Song Cc: Oscar Salvador Cc: Signed-off-by: Andrew Morton --- mm/hugetlb.c | 14 +++++++------- 1 file changed, 7 insertions(+), 7 deletions(-) diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 885017e26fd4..4f6f58bf3db6 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -7332,14 +7332,14 @@ void move_hugetlb_state(struct folio *old_folio, struct folio *new_folio, * There is no need to transfer the per-node surplus state * when we do not cross the node. */ - if (new_nid == old_nid) - return; - spin_lock_irq(&hugetlb_lock); - if (h->surplus_huge_pages_node[old_nid]) { - h->surplus_huge_pages_node[old_nid]--; - h->surplus_huge_pages_node[new_nid]++; + if (new_nid != old_nid) { + spin_lock_irq(&hugetlb_lock); + if (h->surplus_huge_pages_node[old_nid]) { + h->surplus_huge_pages_node[old_nid]--; + h->surplus_huge_pages_node[new_nid]++; + } + spin_unlock_irq(&hugetlb_lock); } - spin_unlock_irq(&hugetlb_lock); } /* -- cgit v1.2.3