Re: [PATCH v2 01/12] mm/debug_vm_pgtable: Introduce struct pgtable_debug_args

[PATCH v2 00/12] mm/debug_vm_pgtable: Enhancements · Gavin Shan <hidden> · 2021-07-19
[PATCH v2 01/12] mm/debug_vm_pgtable: Introduce struct pgtable_debug_args · Gavin Shan <hidden> · 2021-07-19
Re: [PATCH v2 01/12] mm/debug_vm_pgtable: Introduce struct pgtable_debug_args · Gavin Shan <hidden> · 2021-07-19
Re: [PATCH v2 01/12] mm/debug_vm_pgtable: Introduce struct pgtable_debug_args · Anshuman Khandual <hidden> · 2021-07-20
Re: [PATCH v2 01/12] mm/debug_vm_pgtable: Introduce struct pgtable_debug_args · Gavin Shan <hidden> · 2021-07-20
Re: [PATCH v2 01/12] mm/debug_vm_pgtable: Introduce struct pgtable_debug_args · Anshuman Khandual <hidden> · 2021-07-21
Re: [PATCH v2 01/12] mm/debug_vm_pgtable: Introduce struct pgtable_debug_args · Gavin Shan <hidden> · 2021-07-21
[PATCH v2 02/12] mm/debug_vm_pgtable: Use struct pgtable_debug_args in basic tests · Gavin Shan <hidden> · 2021-07-19
[PATCH v2 03/12] mm/debug_vm_pgtable: Use struct pgtable_debug_args in leaf and savewrite tests · Gavin Shan <hidden> · 2021-07-19
[PATCH v2 04/12] mm/debug_vm_pgtable: Use struct pgtable_debug_args in protnone and devmap tests · Gavin Shan <hidden> · 2021-07-19
[PATCH v2 05/12] mm/vm_debug_pgtable: Use struct pgtable_debug_args in soft_dirty and swap tests · Gavin Shan <hidden> · 2021-07-19
[PATCH v2 06/12] mm/debug_vm_pgtable: Use struct pgtable_debug_args in migration and thp tests · Gavin Shan <hidden> · 2021-07-19
[PATCH v2 07/12] mm/debug_vm_pgtable: Use struct pgtable_debug_args in PTE modifying tests · Gavin Shan <hidden> · 2021-07-19
[PATCH v2 08/12] mm/debug_vm_pgtable: Use struct pgtable_debug_args in PMD · Gavin Shan <hidden> · 2021-07-19
[PATCH v2 09/12] mm/vm_debug_pgtable: Use struct pgtable_debug_args in PUD modifying tests · Gavin Shan <hidden> · 2021-07-19
Re: [PATCH v2 09/12] mm/vm_debug_pgtable: Use struct pgtable_debug_args in PUD modifying tests · kernel test robot <hidden> · 2021-07-19
Re: [PATCH v2 09/12] mm/vm_debug_pgtable: Use struct pgtable_debug_args in PUD modifying tests · Gavin Shan <hidden> · 2021-07-19
Re: [PATCH v2 09/12] mm/vm_debug_pgtable: Use struct pgtable_debug_args in PUD modifying tests · kernel test robot <hidden> · 2021-07-20
Re: [PATCH v2 09/12] mm/vm_debug_pgtable: Use struct pgtable_debug_args in PUD modifying tests · Gavin Shan <hidden> · 2021-07-20
[PATCH v2 10/12] mm/debug_vm_pgtable: Use struct pgtable_debug_args in PGD and P4D modifying tests · Gavin Shan <hidden> · 2021-07-19
[PATCH v2 12/12] mm/debug_vm_pgtable: Fix corrupted page flag · Gavin Shan <hidden> · 2021-07-19
[PATCH v2 11/12] mm/debug_vm_pgtable: Remove unused code · Gavin Shan <hidden> · 2021-07-19
Re: [PATCH v2 00/12] mm/debug_vm_pgtable: Enhancements · Gavin Shan <hidden> · 2021-07-19

From: Anshuman Khandual <hidden>
Date: 2021-07-20 06:42:30
Also in: lkml


On 7/19/21 6:31 PM, Gavin Shan wrote:

quoted

+    if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) &&
+        has_transparent_hugepage()) {
+        page = alloc_pages(GFP_KERNEL, HPAGE_PMD_ORDER);
+        if (page) {
+            args->pmd_pfn = page_to_pfn(page);
+            args->pte_pfn = args->pmd_pfn;
+            return 0;
+        }
+    }
+

As syzbot reported against v1 series, we could allocate pages larger than (1 << (MAX_ORDER - 1)) here.
So __GFP_NOWARN is needed here. I will fix it in v3 series.

I could find the following build error reported from lkp on V2.

mm/debug_vm_pgtable.c:445:8: warning: variable 'pud' set but not used [-Wunused-but-set-variable]

Could you please point to the syzbot reported problem on V1 as you
have mentioned above. Are there configs where HPAGE_[PMD|PUD]_ORDER
is greater than (MAX_ORDER - 1) ? If yes, how adding __GFP_NOWARN
solves the problem ?

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