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SubjectRe: [PATCH v4 01/12] mm/debug_vm_pgtable: Introduce struct pgtable_debug_args
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Hi Anshuman,

On 7/28/21 5:32 PM, Anshuman Khandual wrote:
> On 7/27/21 11:43 AM, Gavin Shan wrote:
>> In debug_vm_pgtable(), there are many local variables introduced to
>> track the needed information and they are passed to the functions for
>> various test cases. It'd better to introduce a struct as place holder
>> for these information. With it, what the tests functions need is the
>> struct. In this way, the code is simplified and easier to be maintained.
>>
>> Besides, set_xxx_at() could access the data on the corresponding pages
>> in the page table modifying tests. So the accessed pages in the tests
>> should have been allocated from buddy. Otherwise, we're accessing pages
>> that aren't owned by us. This causes issues like page flag corruption
>> or kernel crash on accessing unmapped page when CONFIG_DEBUG_PAGEALLOC
>> is enabled.
>>
>> This introduces "struct pgtable_debug_args". The struct is initialized
>> and destroyed, but the information in the struct isn't used yet. It will
>> be used in subsequent patches.
>>
>> Signed-off-by: Gavin Shan <gshan@redhat.com>
>> ---
>> mm/debug_vm_pgtable.c | 280 +++++++++++++++++++++++++++++++++++++++++-
>> 1 file changed, 279 insertions(+), 1 deletion(-)
>>
>> diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c
>> index 1c922691aa61..8c7361643166 100644
>> --- a/mm/debug_vm_pgtable.c
>> +++ b/mm/debug_vm_pgtable.c
>> @@ -58,6 +58,37 @@
>> #define RANDOM_ORVALUE (GENMASK(BITS_PER_LONG - 1, 0) & ~ARCH_SKIP_MASK)
>> #define RANDOM_NZVALUE GENMASK(7, 0)
>>
>> +struct pgtable_debug_args {
>> + struct mm_struct *mm;
>> + struct vm_area_struct *vma;
>> +
>> + pgd_t *pgdp;
>> + p4d_t *p4dp;
>> + pud_t *pudp;
>> + pmd_t *pmdp;
>> + pte_t *ptep;
>> +
>> + p4d_t *start_p4dp;
>> + pud_t *start_pudp;
>> + pmd_t *start_pmdp;
>> + pgtable_t start_ptep;
>> +
>> + unsigned long vaddr;
>> + pgprot_t page_prot;
>> + pgprot_t page_prot_none;
>> +
>> + bool is_contiguous_page;
>> + unsigned long pud_pfn;
>> + unsigned long pmd_pfn;
>> + unsigned long pte_pfn;
>> +
>> + unsigned long fixed_pgd_pfn;
>> + unsigned long fixed_p4d_pfn;
>> + unsigned long fixed_pud_pfn;
>> + unsigned long fixed_pmd_pfn;
>> + unsigned long fixed_pte_pfn;
>> +};
>> +
>> static void __init pte_basic_tests(unsigned long pfn, int idx)
>> {
>> pgprot_t prot = protection_map[idx];
>> @@ -955,8 +986,249 @@ static unsigned long __init get_random_vaddr(void)
>> return random_vaddr;
>> }
>>
>> +static void __init destroy_args(struct pgtable_debug_args *args)
>> +{
>> + struct page *page = NULL;
>> +
>> + /* Free (huge) page */
>> + if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) &&
>> + IS_ENABLED(CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD) &&
>> + has_transparent_hugepage() &&
>> + args->pud_pfn != ULONG_MAX) {
>> + if (args->is_contiguous_page) {
>> + free_contig_range(args->pud_pfn,
>> + (1 << (HPAGE_PUD_SHIFT - PAGE_SHIFT)));
>> + } else {
>> + page = pfn_to_page(args->pud_pfn);
>> + __free_pages(page, HPAGE_PUD_SHIFT - PAGE_SHIFT);
>> + }
>> +
>> + args->pud_pfn = ULONG_MAX;
>> + args->pmd_pfn = ULONG_MAX;
>> + args->pte_pfn = ULONG_MAX;
>> + }
>> +
>> + if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) &&
>> + has_transparent_hugepage() &&
>> + args->pmd_pfn != ULONG_MAX) {
>> + if (args->is_contiguous_page) {
>> + free_contig_range(args->pmd_pfn, (1 << HPAGE_PMD_ORDER));
>> + } else {
>> + page = pfn_to_page(args->pmd_pfn);
>> + __free_pages(page, HPAGE_PMD_ORDER);
>> + }
>> +
>> + args->pmd_pfn = ULONG_MAX;
>> + args->pte_pfn = ULONG_MAX;
>> + }
>> +
>> + if (args->pte_pfn != ULONG_MAX) {
>> + page = pfn_to_page(args->pte_pfn);
>> + __free_pages(page, 0);
>> + }
>> +
>> + /* Free page table entries */
>> + if (args->start_ptep) {
>> + pte_free(args->mm, args->start_ptep);
>> + mm_dec_nr_ptes(args->mm);
>> + }
>> +
>> + if (args->start_pmdp) {
>> + pmd_free(args->mm, args->start_pmdp);
>> + mm_dec_nr_pmds(args->mm);
>> + }
>> +
>> + if (args->start_pudp) {
>> + pud_free(args->mm, args->start_pudp);
>> + mm_dec_nr_puds(args->mm);
>> + }
>> +
>> + if (args->start_p4dp)
>> + p4d_free(args->mm, args->p4dp);
>
> ^^^^ s/args->p4dp/args->start_p4dp ?
>

Yes, It should be "args->start_p4dp" here. I will correct it in v5
after you finish review on v4.

Thanks,
Gavin

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