On 10/30/26 11:15, Ritesh Harjani (IBM) wrote: > "David Hildenbrand (Arm)" <[email protected]> writes: > >> On 10/30/26 01:07, Ritesh Harjani (IBM) wrote: >>> 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 <[email protected]> >>> Signed-off-by: Ritesh Harjani (IBM) <[email protected]> >>> --- >>> [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 Patch-1 is now superseded by a different 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.l...@gmail.com/ >>> [2]: >>> https://lore.kernel.org/all/[email protected]/ >>> >>> 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 >>> >> >> >> Matches zap_huge_pmd(). >> >> I will wait a bit and then queue this shortly. >> > > Thanks David, however, looks like Andrew might have queued this up in > his mm tree [1], right? > > [1]: https://lore.kernel.org/all/[email protected]/
No worries, one of us can drop it before sending it upstream. I'm about to send out the MAINTAINTERS update in a bit, so right now it's still confusing. (but also there is no harm in having it in two trees temporarily) > >> This sounds like stable material? >> > > Sorry, my bad. Yes, we should have this Cc: [email protected]. > > Kindly let me know if I should update the tag and send v3, or can it be > taken care? Thanks! I would just apply that when picking, no need to resend. Thanks! -- Cheers, David
