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Subject: Re: [PATCH v3 08/12] mm/debug_vm_pgtable: Use struct
 pgtable_debug_args in PMD modifying tests
To:     Gavin Shan <gshan@redhat.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>
 <20210719130613.334901-9-gshan@redhat.com>
 <52a61d4a-f93d-af9e-4a34-d8ea7c476838@arm.com>
 <e2707943-8645-a6d5-be15-7cf56791fedb@redhat.com>
From:   Anshuman Khandual <anshuman.khandual@arm.com>
Message-ID: <876f9722-c307-560d-5efd-3613c312c7bd@arm.com>
Date:   Thu, 22 Jul 2021 12:41:26 +0530
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On 7/22/21 12:11 PM, Gavin Shan wrote:
> 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@redhat.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'.

Why ? Just the evaluation of 'pmd_aligned' from 'paddr' should
be enough to avoid such warning. 'pmd_aligned' need not be used
afterwards.