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 does.
Fixes: dbe54153296d0 ("mm/huge_memory: add vmf_insert_folio_pud()")
Reported-by: Pavithra <[email protected]>
Signed-off-by: Ritesh Harjani (IBM) <[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
