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Date:   Thu, 22 Jul 2021 16:41:30 +1000
From:   Gavin Shan <gshan@...hat.com>
To:     Anshuman Khandual <anshuman.khandual@....com>, linux-mm@...ck.org
Cc:     linux-kernel@...r.kernel.org, catalin.marinas@....com,
        will@...nel.org, akpm@...ux-foundation.org, chuhu@...hat.com,
        shan.gavin@...il.com
Subject: Re: [PATCH v3 08/12] mm/debug_vm_pgtable: Use struct
 pgtable_debug_args in PMD modifying tests

Hi Anshuman,

On 7/22/21 3:45 PM, Anshuman Khandual wrote:
> On 7/19/21 6:36 PM, Gavin Shan wrote:
>> This uses struct pgtable_debug_args in PMD modifying tests. The allocated
>> huge page is used when set_pmd_at() is used. The corresponding tests
>> are skipped if the huge page doesn't exist. Besides, the unused variable
>> @pmd_aligned in debug_vm_pgtable() is dropped.
> 
> Please dont drop @pmd_aligned just yet.
> 

We need do so. Otherwise, there is build warning to complain
something like 'unused variable' after this patch is applied.

>>
>> Signed-off-by: Gavin Shan <gshan@...hat.com>
>> ---
>>   mm/debug_vm_pgtable.c | 102 ++++++++++++++++++++----------------------
>>   1 file changed, 48 insertions(+), 54 deletions(-)
>>
>> diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c
>> index eb6dda88e0d9..cec3cbf99a6b 100644
>> --- a/mm/debug_vm_pgtable.c
>> +++ b/mm/debug_vm_pgtable.c
>> @@ -213,54 +213,54 @@ static void __init pmd_basic_tests(struct pgtable_debug_args *args, int idx)
>>   	WARN_ON(!pmd_bad(pmd_mkhuge(pmd)));
>>   }
>>   
>> -static void __init pmd_advanced_tests(struct mm_struct *mm,
>> -				      struct vm_area_struct *vma, pmd_t *pmdp,
>> -				      unsigned long pfn, unsigned long vaddr,
>> -				      pgprot_t prot, pgtable_t pgtable)
>> +static void __init pmd_advanced_tests(struct pgtable_debug_args *args)
>>   {
>>   	pmd_t pmd;
>> +	unsigned long vaddr = (args->vaddr & HPAGE_PMD_MASK);
>>   
>>   	if (!has_transparent_hugepage())
>>   		return;
>>   
>>   	pr_debug("Validating PMD advanced\n");
>> -	/* Align the address wrt HPAGE_PMD_SIZE */
>> -	vaddr &= HPAGE_PMD_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->pmd_pfn == ULONG_MAX) {
>> +		pr_debug("%s: Skipped\n", __func__);
>> +		return;
>> +	}
> 
> Just return. Please dont call out "Skipped".
> 

Ok.

>>   
>> -	pgtable_trans_huge_deposit(mm, pmdp, pgtable);
>> +	pgtable_trans_huge_deposit(args->mm, args->pmdp, args->start_ptep);
>>   
>> -	pmd = pfn_pmd(pfn, prot);
>> -	set_pmd_at(mm, vaddr, pmdp, pmd);
>> -	pmdp_set_wrprotect(mm, vaddr, pmdp);
>> -	pmd = READ_ONCE(*pmdp);
>> +	pmd = pfn_pmd(args->pmd_pfn, args->page_prot);
>> +	set_pmd_at(args->mm, vaddr, args->pmdp, pmd);
>> +	pmdp_set_wrprotect(args->mm, vaddr, args->pmdp);
>> +	pmd = READ_ONCE(*(args->pmdp));
>>   	WARN_ON(pmd_write(pmd));
>> -	pmdp_huge_get_and_clear(mm, vaddr, pmdp);
>> -	pmd = READ_ONCE(*pmdp);
>> +	pmdp_huge_get_and_clear(args->mm, vaddr, args->pmdp);
>> +	pmd = READ_ONCE(*(args->pmdp));
>>   	WARN_ON(!pmd_none(pmd));
>>   
>> -	pmd = pfn_pmd(pfn, prot);
>> +	pmd = pfn_pmd(args->pmd_pfn, args->page_prot);
>>   	pmd = pmd_wrprotect(pmd);
>>   	pmd = pmd_mkclean(pmd);
>> -	set_pmd_at(mm, vaddr, pmdp, pmd);
>> +	set_pmd_at(args->mm, vaddr, args->pmdp, pmd);
>>   	pmd = pmd_mkwrite(pmd);
>>   	pmd = pmd_mkdirty(pmd);
>> -	pmdp_set_access_flags(vma, vaddr, pmdp, pmd, 1);
>> -	pmd = READ_ONCE(*pmdp);
>> +	pmdp_set_access_flags(args->vma, vaddr, args->pmdp, pmd, 1);
>> +	pmd = READ_ONCE(*(args->pmdp));
>>   	WARN_ON(!(pmd_write(pmd) && pmd_dirty(pmd)));
>> -	pmdp_huge_get_and_clear_full(vma, vaddr, pmdp, 1);
>> -	pmd = READ_ONCE(*pmdp);
>> +	pmdp_huge_get_and_clear_full(args->vma, vaddr, args->pmdp, 1);
>> +	pmd = READ_ONCE(*(args->pmdp));
>>   	WARN_ON(!pmd_none(pmd));
>>   
>> -	pmd = pmd_mkhuge(pfn_pmd(pfn, prot));
>> +	pmd = pmd_mkhuge(pfn_pmd(args->pmd_pfn, args->page_prot));
>>   	pmd = pmd_mkyoung(pmd);
>> -	set_pmd_at(mm, vaddr, pmdp, pmd);
>> -	pmdp_test_and_clear_young(vma, vaddr, pmdp);
>> -	pmd = READ_ONCE(*pmdp);
>> +	set_pmd_at(args->mm, vaddr, args->pmdp, pmd);
>> +	pmdp_test_and_clear_young(args->vma, vaddr, args->pmdp);
>> +	pmd = READ_ONCE(*(args->pmdp));
>>   	WARN_ON(pmd_young(pmd));
>>   
>>   	/*  Clear the pte entries  */
>> -	pmdp_huge_get_and_clear(mm, vaddr, pmdp);
>> -	pgtable = pgtable_trans_huge_withdraw(mm, pmdp);
>> +	pmdp_huge_get_and_clear(args->mm, vaddr, args->pmdp);
>> +	pgtable_trans_huge_withdraw(args->mm, args->pmdp);
>>   }
>>   
>>   static void __init pmd_leaf_tests(struct pgtable_debug_args *args)
>> @@ -417,12 +417,7 @@ static void __init pud_leaf_tests(struct pgtable_debug_args *args) { }
>>   #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 mm_struct *mm,
>> -				      struct vm_area_struct *vma, pmd_t *pmdp,
>> -				      unsigned long pfn, unsigned long vaddr,
>> -				      pgprot_t prot, pgtable_t pgtable)
>> -{
>> -}
>> +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,
>> @@ -435,11 +430,11 @@ static void __init pmd_savedwrite_tests(struct pgtable_debug_args *args) { }
>>   #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
>>   
>>   #ifdef CONFIG_HAVE_ARCH_HUGE_VMAP
>> -static void __init pmd_huge_tests(pmd_t *pmdp, unsigned long pfn, pgprot_t prot)
>> +static void __init pmd_huge_tests(struct pgtable_debug_args *args)
>>   {
>>   	pmd_t pmd;
>>   
>> -	if (!arch_vmap_pmd_supported(prot))
>> +	if (!arch_vmap_pmd_supported(args->page_prot))
>>   		return;
>>   
>>   	pr_debug("Validating PMD huge\n");
>> @@ -447,10 +442,11 @@ static void __init pmd_huge_tests(pmd_t *pmdp, unsigned long pfn, pgprot_t prot)
>>   	 * X86 defined pmd_set_huge() verifies that the given
>>   	 * PMD is not a populated non-leaf entry.
>>   	 */
>> -	WRITE_ONCE(*pmdp, __pmd(0));
>> -	WARN_ON(!pmd_set_huge(pmdp, __pfn_to_phys(pfn), prot));
>> -	WARN_ON(!pmd_clear_huge(pmdp));
>> -	pmd = READ_ONCE(*pmdp);
>> +	WRITE_ONCE(*(args->pmdp), __pmd(0));
> 
> Possible extra braces.
> 

Will drop it in v4, thanks!

>> +	WARN_ON(!pmd_set_huge(args->pmdp, __pfn_to_phys(args->fixed_pmd_pfn),
>> +			      args->page_prot));
> 
> Dont break the line.
> 

Ok.

>> +	WARN_ON(!pmd_clear_huge(args->pmdp));
>> +	pmd = READ_ONCE(*(args->pmdp));
>>   	WARN_ON(!pmd_none(pmd));
>>   }
>>   
>> @@ -473,7 +469,7 @@ static void __init pud_huge_tests(pud_t *pudp, unsigned long pfn, pgprot_t prot)
>>   	WARN_ON(!pud_none(pud));
>>   }
>>   #else /* !CONFIG_HAVE_ARCH_HUGE_VMAP */
>> -static void __init pmd_huge_tests(pmd_t *pmdp, unsigned long pfn, pgprot_t prot) { }
>> +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) { }
>>   #endif /* CONFIG_HAVE_ARCH_HUGE_VMAP */
>>   
>> @@ -640,20 +636,19 @@ static void __init pte_clear_tests(struct pgtable_debug_args *args)
>>   	WARN_ON(!pte_none(pte));
>>   }
>>   
>> -static void __init pmd_clear_tests(struct mm_struct *mm, pmd_t *pmdp)
>> +static void __init pmd_clear_tests(struct pgtable_debug_args *args)
>>   {
>> -	pmd_t pmd = READ_ONCE(*pmdp);
>> +	pmd_t pmd = READ_ONCE(*(args->pmdp));
>>   
>>   	pr_debug("Validating PMD clear\n");
>>   	pmd = __pmd(pmd_val(pmd) | RANDOM_ORVALUE);
>> -	WRITE_ONCE(*pmdp, pmd);
>> -	pmd_clear(pmdp);
>> -	pmd = READ_ONCE(*pmdp);
>> +	WRITE_ONCE(*(args->pmdp), pmd);
>> +	pmd_clear(args->pmdp);
>> +	pmd = READ_ONCE(*(args->pmdp));
>>   	WARN_ON(!pmd_none(pmd));
>>   }
>>   
>> -static void __init pmd_populate_tests(struct mm_struct *mm, pmd_t *pmdp,
>> -				      pgtable_t pgtable)
>> +static void __init pmd_populate_tests(struct pgtable_debug_args *args)
>>   {
>>   	pmd_t pmd;
>>   
>> @@ -662,8 +657,8 @@ static void __init pmd_populate_tests(struct mm_struct *mm, pmd_t *pmdp,
>>   	 * This entry points to next level page table page.
>>   	 * Hence this must not qualify as pmd_bad().
>>   	 */
>> -	pmd_populate(mm, pmdp, pgtable);
>> -	pmd = READ_ONCE(*pmdp);
>> +	pmd_populate(args->mm, args->pmdp, args->start_ptep);
>> +	pmd = READ_ONCE(*(args->pmdp));
>>   	WARN_ON(pmd_bad(pmd));
>>   }
>>   
>> @@ -1159,7 +1154,7 @@ static int __init debug_vm_pgtable(void)
>>   	pgtable_t saved_ptep;
>>   	pgprot_t prot;
>>   	phys_addr_t paddr;
>> -	unsigned long vaddr, pmd_aligned;
>> +	unsigned long vaddr;
>>   	unsigned long pud_aligned;
>>   	spinlock_t *ptl = NULL;
>>   	int idx, ret;
>> @@ -1194,7 +1189,6 @@ static int __init debug_vm_pgtable(void)
>>   	 */
>>   	paddr = __pa_symbol(&start_kernel);
>>   
>> -	pmd_aligned = (paddr & PMD_MASK) >> PAGE_SHIFT;
> 
> Please dont drop these just yet and wait until [PATCH 11/12].
> 

Otherwise, it causes build warning: 'unused variable'.

>>   	pud_aligned = (paddr & PUD_MASK) >> PAGE_SHIFT;
>>   
>>   	pgdp = pgd_offset(mm, vaddr);
>> @@ -1281,11 +1275,11 @@ static int __init debug_vm_pgtable(void)
>>   	pte_advanced_tests(&args);
>>   	spin_unlock(ptl);
>>   
>> -	ptl = pmd_lock(mm, pmdp);
>> -	pmd_clear_tests(mm, pmdp);
>> -	pmd_advanced_tests(mm, vma, pmdp, pmd_aligned, vaddr, prot, saved_ptep);
>> -	pmd_huge_tests(pmdp, pmd_aligned, prot);
>> -	pmd_populate_tests(mm, pmdp, saved_ptep);
>> +	ptl = pmd_lock(args.mm, args.pmdp);
>> +	pmd_clear_tests(&args);
>> +	pmd_advanced_tests(&args);
>> +	pmd_huge_tests(&args);
>> +	pmd_populate_tests(&args);
>>   	spin_unlock(ptl);
>>   
>>   	ptl = pud_lock(mm, pudp);
>>
> 

Thanks,
Gavin

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