Re: [PATCH v3 09/12] mm/debug_vm_pgtable: Use struct pgtable_debug_args in PUD modifying tests

[Gavin Shan <gshan@xxxxxxxxxx>]

Hi Anshuman,

On 7/22/21 3:39 PM, Anshuman Khandual wrote:
> On 7/19/21 6:36 PM, Gavin Shan wrote:
> > This uses struct pgtable_debug_args in PUD modifying tests. The allocated
> > huge page is used when set_pud_at() is used. The corresponding tests
> > are skipped if the huge page doesn't exist. Besides, the following unused
> > variables in debug_vm_pgtable() are dropped: @prot, @paddr, @pud_aligned.
>
> Please dont drop @prot, @paddr, @pud_aligned just yet.

Otherwise it will cause build warning ("unused variable") as
explain in previous reply.

> > Signed-off-by: Gavin Shan <gshan@xxxxxxxxxx>
> > ---
> >   mm/debug_vm_pgtable.c | 130 ++++++++++++++++--------------------------
> >   1 file changed, 50 insertions(+), 80 deletions(-)
> >
> > diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c
> > index cec3cbf99a6b..57b7ead0708b 100644
> > --- a/mm/debug_vm_pgtable.c
> > +++ b/mm/debug_vm_pgtable.c
> > @@ -338,55 +338,55 @@ static void __init pud_basic_tests(struct pgtable_debug_args *args, int idx)
> >   	WARN_ON(!pud_bad(pud_mkhuge(pud)));
> >   }
> >   
> > -static void __init pud_advanced_tests(struct mm_struct *mm,
> > -				      struct vm_area_struct *vma, pud_t *pudp,
> > -				      unsigned long pfn, unsigned long vaddr,
> > -				      pgprot_t prot)
> > +static void __init pud_advanced_tests(struct pgtable_debug_args *args)
> >   {
> > +	unsigned long vaddr = (args->vaddr & HPAGE_PUD_MASK);
> >   	pud_t pud;
> >   
> >   	if (!has_transparent_hugepage())
> >   		return;
> >   
> >   	pr_debug("Validating PUD advanced\n");
> > -	/* Align the address wrt HPAGE_PUD_SIZE */
> > -	vaddr &= HPAGE_PUD_MASK;
>
> Please just leave these unchanged. If has_transparent_hugepage() evaluates
> negative, it skips the masking operation. As mentioned earlier please avoid
> changing the test in any manner during these transition patches.

Ok.

> > +	if (args->pud_pfn == ULONG_MAX) {
> > +		pr_debug("%s: Skipped\n", __func__);
>
> Just return. Please dont call out "Skipped". Applicable for all transition
> patches here.

Ok.

> > +		return;
> > +	}
> >   
> > -	pud = pfn_pud(pfn, prot);
> > -	set_pud_at(mm, vaddr, pudp, pud);
> > -	pudp_set_wrprotect(mm, vaddr, pudp);
> > -	pud = READ_ONCE(*pudp);
> > +	pud = pfn_pud(args->pud_pfn, args->page_prot);
> > +	set_pud_at(args->mm, vaddr, args->pudp, pud);
> > +	pudp_set_wrprotect(args->mm, vaddr, args->pudp);
> > +	pud = READ_ONCE(*(args->pudp));
>
> Seems like an extra braces while de-referencing arg->pudp. Could these be
> dropped. Just READ_ONCE(*args->pudp).

Ok. Will be dropped in v4.

> >   	WARN_ON(pud_write(pud));
> >   
> >   #ifndef __PAGETABLE_PMD_FOLDED
> > -	pudp_huge_get_and_clear(mm, vaddr, pudp);
> > -	pud = READ_ONCE(*pudp);
> > +	pudp_huge_get_and_clear(args->mm, vaddr, args->pudp);
> > +	pud = READ_ONCE(*(args->pudp));
> >   	WARN_ON(!pud_none(pud));
> >   #endif /* __PAGETABLE_PMD_FOLDED */
> > -	pud = pfn_pud(pfn, prot);
> > +	pud = pfn_pud(args->pud_pfn, args->page_prot);
> >   	pud = pud_wrprotect(pud);
> >   	pud = pud_mkclean(pud);
> > -	set_pud_at(mm, vaddr, pudp, pud);
> > +	set_pud_at(args->mm, vaddr, args->pudp, pud);
> >   	pud = pud_mkwrite(pud);
> >   	pud = pud_mkdirty(pud);
> > -	pudp_set_access_flags(vma, vaddr, pudp, pud, 1);
> > -	pud = READ_ONCE(*pudp);
> > +	pudp_set_access_flags(args->vma, vaddr, args->pudp, pud, 1);
> > +	pud = READ_ONCE(*(args->pudp));
> >   	WARN_ON(!(pud_write(pud) && pud_dirty(pud)));
> >   
> >   #ifndef __PAGETABLE_PMD_FOLDED
> > -	pudp_huge_get_and_clear_full(mm, vaddr, pudp, 1);
> > -	pud = READ_ONCE(*pudp);
> > +	pudp_huge_get_and_clear_full(args->mm, vaddr, args->pudp, 1);
> > +	pud = READ_ONCE(*(args->pudp));
> >   	WARN_ON(!pud_none(pud));
> >   #endif /* __PAGETABLE_PMD_FOLDED */
> >   
> > -	pud = pfn_pud(pfn, prot);
> > +	pud = pfn_pud(args->pud_pfn, args->page_prot);
> >   	pud = pud_mkyoung(pud);
> > -	set_pud_at(mm, vaddr, pudp, pud);
> > -	pudp_test_and_clear_young(vma, vaddr, pudp);
> > -	pud = READ_ONCE(*pudp);
> > +	set_pud_at(args->mm, vaddr, args->pudp, pud);
> > +	pudp_test_and_clear_young(args->vma, vaddr, args->pudp);
> > +	pud = READ_ONCE(*(args->pudp));
> >   	WARN_ON(pud_young(pud));
> >   
> > -	pudp_huge_get_and_clear(mm, vaddr, pudp);
> > +	pudp_huge_get_and_clear(args->mm, vaddr, args->pudp);
> >   }
> >   
> >   static void __init pud_leaf_tests(struct pgtable_debug_args *args)
> > @@ -406,24 +406,14 @@ static void __init pud_leaf_tests(struct pgtable_debug_args *args)
> >   }
> >   #else  /* !CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
> >   static void __init pud_basic_tests(struct pgtable_debug_args *args, int idx) { }
> > -static void __init pud_advanced_tests(struct mm_struct *mm,
> > -				      struct vm_area_struct *vma, pud_t *pudp,
> > -				      unsigned long pfn, unsigned long vaddr,
> > -				      pgprot_t prot)
> > -{
> > -}
> > +static void __init pud_advanced_tests(struct pgtable_debug_args *args) { }
> >   static void __init pud_leaf_tests(struct pgtable_debug_args *args) { }
> >   #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
> >   #else  /* !CONFIG_TRANSPARENT_HUGEPAGE */
> >   static void __init pmd_basic_tests(struct pgtable_debug_args *args, int idx) { }
> >   static void __init pud_basic_tests(struct pgtable_debug_args *args, int idx) { }
> >   static void __init pmd_advanced_tests(struct pgtable_debug_args *args) { }
> > -static void __init pud_advanced_tests(struct mm_struct *mm,
> > -				      struct vm_area_struct *vma, pud_t *pudp,
> > -				      unsigned long pfn, unsigned long vaddr,
> > -				      pgprot_t prot)
> > -{
> > -}
> > +static void __init pud_advanced_tests(struct pgtable_debug_args *args) { }
> >   static void __init pmd_leaf_tests(struct pgtable_debug_args *args) { }
> >   static void __init pud_leaf_tests(struct pgtable_debug_args *args) { }
> >   static void __init pmd_savedwrite_tests(struct pgtable_debug_args *args) { }
> > @@ -450,11 +440,11 @@ static void __init pmd_huge_tests(struct pgtable_debug_args *args)
> >   	WARN_ON(!pmd_none(pmd));
> >   }
> >   
> > -static void __init pud_huge_tests(pud_t *pudp, unsigned long pfn, pgprot_t prot)
> > +static void __init pud_huge_tests(struct pgtable_debug_args *args)
> >   {
> >   	pud_t pud;
> >   
> > -	if (!arch_vmap_pud_supported(prot))
> > +	if (!arch_vmap_pud_supported(args->page_prot))
> >   		return;
> >   
> >   	pr_debug("Validating PUD huge\n");
> > @@ -462,15 +452,16 @@ static void __init pud_huge_tests(pud_t *pudp, unsigned long pfn, pgprot_t prot)
> >   	 * X86 defined pud_set_huge() verifies that the given
> >   	 * PUD is not a populated non-leaf entry.
> >   	 */
> > -	WRITE_ONCE(*pudp, __pud(0));
> > -	WARN_ON(!pud_set_huge(pudp, __pfn_to_phys(pfn), prot));
> > -	WARN_ON(!pud_clear_huge(pudp));
> > -	pud = READ_ONCE(*pudp);
> > +	WRITE_ONCE(*(args->pudp), __pud(0));
> > +	WARN_ON(!pud_set_huge(args->pudp, __pfn_to_phys(args->fixed_pud_pfn),
> > +			      args->page_prot));
>
> Please dont break the line, we could go upto 100 width. Please do
> the same for the entire series. Improves the readability.
>
> > +	WARN_ON(!pud_clear_huge(args->pudp));
> > +	pud = READ_ONCE(*(args->pudp));
> >   	WARN_ON(!pud_none(pud));
> >   }
> >   #else /* !CONFIG_HAVE_ARCH_HUGE_VMAP */
> >   static void __init pmd_huge_tests(struct pgtable_debug_args *args) { }
> > -static void __init pud_huge_tests(pud_t *pudp, unsigned long pfn, pgprot_t prot) { }
> > +static void __init pud_huge_tests(struct pgtable_debug_args *args) { }
> >   #endif /* CONFIG_HAVE_ARCH_HUGE_VMAP */
> >   
> >   static void __init p4d_basic_tests(void)
> > @@ -492,27 +483,26 @@ static void __init pgd_basic_tests(void)
> >   }
> >   
> >   #ifndef __PAGETABLE_PUD_FOLDED
> > -static void __init pud_clear_tests(struct mm_struct *mm, pud_t *pudp)
> > +static void __init pud_clear_tests(struct pgtable_debug_args *args)
> >   {
> > -	pud_t pud = READ_ONCE(*pudp);
> > +	pud_t pud = READ_ONCE(*(args->pudp));
> >   
> > -	if (mm_pmd_folded(mm))
> > +	if (mm_pmd_folded(args->mm))
> >   		return;
> >   
> >   	pr_debug("Validating PUD clear\n");
> >   	pud = __pud(pud_val(pud) | RANDOM_ORVALUE);
> > -	WRITE_ONCE(*pudp, pud);
> > -	pud_clear(pudp);
> > -	pud = READ_ONCE(*pudp);
> > +	WRITE_ONCE(*(args->pudp), pud);
> > +	pud_clear(args->pudp);
> > +	pud = READ_ONCE(*(args->pudp));
> >   	WARN_ON(!pud_none(pud));
> >   }
> >   
> > -static void __init pud_populate_tests(struct mm_struct *mm, pud_t *pudp,
> > -				      pmd_t *pmdp)
> > +static void __init pud_populate_tests(struct pgtable_debug_args *args)
> >   {
> >   	pud_t pud;
> >   
> > -	if (mm_pmd_folded(mm))
> > +	if (mm_pmd_folded(args->mm))
> >   		return;
> >   
> >   	pr_debug("Validating PUD populate\n");
> > @@ -520,16 +510,13 @@ static void __init pud_populate_tests(struct mm_struct *mm, pud_t *pudp,
> >   	 * This entry points to next level page table page.
> >   	 * Hence this must not qualify as pud_bad().
> >   	 */
> > -	pud_populate(mm, pudp, pmdp);
> > -	pud = READ_ONCE(*pudp);
> > +	pud_populate(args->mm, args->pudp, args->start_pmdp);
> > +	pud = READ_ONCE(*(args->pudp));
> >   	WARN_ON(pud_bad(pud));
> >   }
> >   #else  /* !__PAGETABLE_PUD_FOLDED */
> > -static void __init pud_clear_tests(struct mm_struct *mm, pud_t *pudp) { }
> > -static void __init pud_populate_tests(struct mm_struct *mm, pud_t *pudp,
> > -				      pmd_t *pmdp)
> > -{
> > -}
> > +static void __init pud_clear_tests(struct pgtable_debug_args *args) { }
> > +static void __init pud_populate_tests(struct pgtable_debug_args *args) { }
> >   #endif /* PAGETABLE_PUD_FOLDED */
> >   
> >   #ifndef __PAGETABLE_P4D_FOLDED
> > @@ -1152,10 +1139,7 @@ static int __init debug_vm_pgtable(void)
> >   	pud_t *pudp, *saved_pudp;
> >   	pmd_t *pmdp, *saved_pmdp, pmd;
> >   	pgtable_t saved_ptep;
> > -	pgprot_t prot;
> > -	phys_addr_t paddr;
> >   	unsigned long vaddr;
> > -	unsigned long pud_aligned;
> >   	spinlock_t *ptl = NULL;
> >   	int idx, ret;
> >   
> > @@ -1164,7 +1148,6 @@ static int __init debug_vm_pgtable(void)
> >   	if (ret)
> >   		return ret;
> >   
> > -	prot = vm_get_page_prot(VMFLAGS);
>
> Please dont drop these just yet and wait until [PATCH 11/12].
>
> >   	vaddr = get_random_vaddr();
> >   	mm = mm_alloc();
> >   	if (!mm) {
> > @@ -1178,19 +1161,6 @@ static int __init debug_vm_pgtable(void)
> >   		return 1;
> >   	}
> >   
> > -	/*
> > -	 * PFN for mapping at PTE level is determined from a standard kernel
> > -	 * text symbol. But pfns for higher page table levels are derived by
> > -	 * masking lower bits of this real pfn. These derived pfns might not
> > -	 * exist on the platform but that does not really matter as pfn_pxx()
> > -	 * helpers will still create appropriate entries for the test. This
> > -	 * helps avoid large memory block allocations to be used for mapping
> > -	 * at higher page table levels.
> > -	 */
>
> Please move this comment as is to the right place inside init_args()
> in the first patch itself. If possible all comments should be moved
> during the first patch and just the code remains till [PATCH 11/12].

I will include all comments in PATCH[01/12]. In that case, we won't
introduce more changes to unrelated function (init_args()).

> > -	paddr = __pa_symbol(&start_kernel);
> > -
> > -	pud_aligned = (paddr & PUD_MASK) >> PAGE_SHIFT;
> > -
>
> Please dont drop these just yet and wait until [PATCH 11/12].

Otherwise, it will cause build warning.

> >   	pgdp = pgd_offset(mm, vaddr);
> >   	p4dp = p4d_alloc(mm, pgdp, vaddr);
> >   	pudp = pud_alloc(mm, p4dp, vaddr);
> > @@ -1282,11 +1252,11 @@ static int __init debug_vm_pgtable(void)
> >   	pmd_populate_tests(&args);
> >   	spin_unlock(ptl);
> >   
> > -	ptl = pud_lock(mm, pudp);
> > -	pud_clear_tests(mm, pudp);
> > -	pud_advanced_tests(mm, vma, pudp, pud_aligned, vaddr, prot);
> > -	pud_huge_tests(pudp, pud_aligned, prot);
> > -	pud_populate_tests(mm, pudp, saved_pmdp);
> > +	ptl = pud_lock(args.mm, args.pudp);
> > +	pud_clear_tests(&args);
> > +	pud_advanced_tests(&args);
> > +	pud_huge_tests(&args);
> > +	pud_populate_tests(&args);
> >   	spin_unlock(ptl);
> >   
> >   	spin_lock(&mm->page_table_lock);

Thanks,
Gavin