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Reply-To: Gavin Shan <gshan@redhat.com>
Subject: Re: [PATCH v3 09/12] mm/debug_vm_pgtable: Use struct
 pgtable_debug_args in PUD modifying tests
To:     Anshuman Khandual <anshuman.khandual@arm.com>, linux-mm@kvack.org
Cc:     linux-kernel@vger.kernel.org, catalin.marinas@arm.com,
        will@kernel.org, akpm@linux-foundation.org, chuhu@redhat.com,
        shan.gavin@gmail.com
References: <20210719130613.334901-1-gshan@redhat.com>
 <20210719130613.334901-10-gshan@redhat.com>
 <8997bf56-ff67-060d-c25b-91e11f31e88a@arm.com>
From:   Gavin Shan <gshan@redhat.com>
Message-ID: <49ced5c2-5001-9cb7-663e-0d0845f1890a@redhat.com>
Date:   Thu, 22 Jul 2021 16:47:27 +1000
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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@redhat.com>
>> ---
>>   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