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Thu, 29 Oct 2026 17:07:48 -0700 (PDT) Received: from pve-server.rlab ([49.205.216.49]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-36a42669128sm2111682eec.3.2026.10.29.17.07.44 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 29 Oct 2026 17:07:48 -0700 (PDT) From: "Ritesh Harjani (IBM)" To: linux-mm@kvack.org, Andrew Morton Cc: Madhavan Srinivasan , Venkat Rao Bagalkote , linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, David Hildenbrand , Muchun Song , Zi Yan , Baolin Wang , "Ritesh Harjani (IBM)" , Pavithra Subject: [PATCHv2] mm/huge_memory: set the mmu_gather page size in zap_huge_pud() Date: Fri, 30 Oct 2026 05:37:36 +0530 Message-Id: <8b853e5f9f16145859407b28af654b0f79e12642.1793318297.git.ritesh.list@gmail.com> X-Mailer: git-send-email 2.39.5 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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()") Reported-by: Pavithra Signed-off-by: Ritesh Harjani (IBM) --- [v1]->v2: ========= - Split the 2 part patch series. Patch-1 is now superseded by a different patch from Muchun which he already posted [2]. - No difference in this patch from v1. [v1]: https://lore.kernel.org/all/97f85592bb78a273be8519e6897e7f9b9bd31469.1793070429.git.ritesh.list@gmail.com/ [2]: https://lore.kernel.org/all/20261029063601.1961415-1-songmuchun@bytedance.com/ mm/huge_memory.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index bd44d58e8684..7e589a2fb02d 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -3040,6 +3040,8 @@ 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; -- 2.39.5