"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 Patch-1 is now superseded by a different 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]/ > 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! -ritesh
