Re: [PATCH v4 01/12] mm/debug_vm_pgtable: Introduce struct pgtable_debug_args

[Gavin Shan]

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@xxxxxxxxxx>
> > ---
> >   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