From 466d6844c8f19fba16b668b49861bdb8d7ded282 Mon Sep 17 00:00:00 2001 From: "Ritesh Harjani (IBM)" Date: Fri, 30 Oct 2026 05:37:36 +0530 Subject: [PATCH] mm/huge_memory: set the mmu_gather page size in zap_huge_pud() Unmapping a device-dax mapping with 1G alignment on powerpc radix kernel built with CONFIG_DEBUG_VM triggers this warning on every munmap: WARNING: mm/mmu_gather.c:176 at __tlb_remove_folio_pages_size+0x38/0x230 NIP [c00000000063d508] __tlb_remove_folio_pages_size+0x38/0x230 LR [c0000000006fb688] zap_huge_pud+0x1b8/0x2d0 Call Trace: zap_huge_pud+0x170/0x2d0 (unreliable) __zap_vma_range+0x1604/0x1e20 unmap_vmas+0xa0/0x1f0 unmap_region+0xb0/0x130 vms_complete_munmap_vmas+0x120/0x310 do_vmi_align_munmap+0x1ec/0x240 __vm_munmap+0x148/0x220 sys_munmap+0x28/0x40 To trigger this - it is enough to mmap() /dev/dax0.0, touch the first byte so that the whole 1G is mapped by a single PUD and then munmap() it. PowerPC needs MMU_GATHER_PAGE_SIZE in which mmu_gather needs to record the page size for which tlb flush is needed. zap_huge_pmd(), zap_pte_range(), change_huge_pud() etc all do this already. However, since commit: dbe54153296d ("mm/huge_memory: add vmf_insert_folio_pud()") a device-dax PUD maps a real folio and zap_huge_pud() now hands it to tlb_remove_page_size(tlb, page, HPAGE_PUD_SIZE). At that point tlb->page_size is still whatever the previous user left behind, which is 0 for the fresh gather set up by munmap() and so the check fires. Fix this in the same way like how other similar paths do. Fixes: dbe54153296d0 ("mm/huge_memory: add vmf_insert_folio_pud()") Cc: stable@vger.kernel.org Reported-by: Pavithra Signed-off-by: Ritesh Harjani (IBM) Acked-by: Zi Yan Acked-by: Muchun Song Tested-by: Pavithra Prakash Link: https://patch.msgid.link/8b853e5f9f16145859407b28af654b0f79e12642.1793318297.git.ritesh.list@gmail.com Signed-off-by: David Hildenbrand (Arm) --- mm/huge_memory.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 7de94775a359..eb913acb03b7 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -3049,6 +3049,8 @@ int zap_huge_pud(struct mmu_gather *tlb, struct vm_area_struct *vma, spinlock_t *ptl; pud_t orig_pud; + tlb_change_page_size(tlb, HPAGE_PUD_SIZE); + ptl = __pud_trans_huge_lock(pud, vma); if (!ptl) return 0;