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Message-ID: <68b6ab2a-4b6d-a0b8-f753-01fdc165b24a@arm.com>
Date: Fri, 23 Jul 2021 08:03:48 +0530
From: Anshuman Khandual <anshuman.khandual@....com>
To: Gavin Shan <gshan@...hat.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
On 7/23/21 6:30 AM, Gavin Shan wrote:
> Hi Anshuman,
>
> On 7/22/21 5:11 PM, Anshuman Khandual wrote:
>> On 7/22/21 12:11 PM, Gavin Shan wrote:
>>> 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'.
>>
>> Why ? Just the evaluation of 'pmd_aligned' from 'paddr' should
>> be enough to avoid such warning. 'pmd_aligned' need not be used
>> afterwards.
>>
>
> It's not enough to avoid the warning. I apply the patches till
> this one (PATCH[v3 08/12]) and have additional code to keep
> @pmd_aligned, then I run into build warning as below:
>
> diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c
> index cec3cbf99a6b..961c9bb6fc7c 100644
> --- a/mm/debug_vm_pgtable.c
> +++ b/mm/debug_vm_pgtable.c
> @@ -1154,7 +1154,7 @@ static int __init debug_vm_pgtable(void)
> pgtable_t saved_ptep;
> pgprot_t prot;
> phys_addr_t paddr;
> - unsigned long vaddr;
> + unsigned long vaddr, pmd_aligned;
> unsigned long pud_aligned;
> spinlock_t *ptl = NULL;
> int idx, ret;
> @@ -1189,6 +1189,7 @@ static int __init debug_vm_pgtable(void)
> */
> paddr = __pa_symbol(&start_kernel);
>
> + pmd_aligned = (paddr & PMD_MASK) >> PAGE_SHIFT;
> pud_aligned = (paddr & PUD_MASK) >> PAGE_SHIFT;
>
> pgdp = pgd_offset(mm, vaddr);
>
> [gwshan@...an l]$ make W=1 mm/debug_vm_pgtable.o
> :
> mm/debug_vm_pgtable.c: In function ‘debug_vm_pgtable’:
> mm/debug_vm_pgtable.c:1157:23: warning: variable ‘pmd_aligned’ set but not used [-Wunused-but-set-variable]
> 1157 | unsigned long vaddr, pmd_aligned;
> | ^~~~~~~~~~~
>
>
> By the way, 0-day is trying to build kernel with "W=1". It means the
> build warnings will be reported by 0-day if the unused variables aren't
> dropped from individual patches. It makes the review a bit harder. However,
It is not about keeping the review process simple. But rather the proposed
patch changing as much what is really required and nothing else.
> we still need to keep each individual patch complete to make 'git bisect'
> friendly.
With W=1 if this throws up a build error, I guess we dont have choice here.
We need to keep the build clean for each individual patch applies.
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