On 08/12/2020 12:03 PM, Aneesh Kumar K.V wrote:
> Saved write support was added to track the write bit of a pte after marking the
> pte protnone. This was done so that AUTONUMA can convert a write pte to protnone
> and still track the old write bit. When converting it back we set the pte write
> bit correctly thereby avoiding a write fault again. Hence enable the test only
> when CONFIG_NUMA_BALANCING is enabled.
This has not been a problem on architectures that do not define pxx_savedwrite()
as they fallback on standard pxx_write() helpers. But ppc64 defines a fall back
for pte_savedwrite() when !CONFIG_NUMA_BALANCING, which always returns false.
Agreed, it makes sense to add CONFIG_NUMA_BALANCING check. But a simple runtime
check will do as the functions are always visible/defined.
if (!IS_ENABLED(CONFIG_NUMA_BALANCING))
return;
>
> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxx>
> ---
> mm/debug_vm_pgtable.c | 7 +++++++
> 1 file changed, 7 insertions(+)
>
> diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c
> index 679bb3d289a3..de8a62d0a931 100644
> --- a/mm/debug_vm_pgtable.c
> +++ b/mm/debug_vm_pgtable.c
> @@ -110,6 +110,7 @@ static void __init pte_advanced_tests(struct mm_struct *mm,
> WARN_ON(pte_young(pte));
> }
>
> +#ifdef CONFIG_NUMA_BALANCING
> static void __init pte_savedwrite_tests(unsigned long pfn, pgprot_t prot)
> {
> pte_t pte = pfn_pte(pfn, prot);
> @@ -118,6 +119,8 @@ static void __init pte_savedwrite_tests(unsigned long pfn, pgprot_t prot)
> WARN_ON(!pte_savedwrite(pte_mk_savedwrite(pte_clear_savedwrite(pte))));
> WARN_ON(pte_savedwrite(pte_clear_savedwrite(pte_mk_savedwrite(pte))));
> }
> +#endif
> +
> #ifdef CONFIG_TRANSPARENT_HUGEPAGE
> static void __init pmd_basic_tests(unsigned long pfn, pgprot_t prot)
> {
> @@ -221,6 +224,7 @@ static void __init pmd_huge_tests(pmd_t *pmdp, unsigned long pfn, pgprot_t prot)
> WARN_ON(!pmd_none(pmd));
> }
>
> +#ifdef CONFIG_NUMA_BALANCING
> static void __init pmd_savedwrite_tests(unsigned long pfn, pgprot_t prot)
> {
> pmd_t pmd = pfn_pmd(pfn, prot);
> @@ -229,6 +233,7 @@ static void __init pmd_savedwrite_tests(unsigned long pfn, pgprot_t prot)
> WARN_ON(!pmd_savedwrite(pmd_mk_savedwrite(pmd_clear_savedwrite(pmd))));
> WARN_ON(pmd_savedwrite(pmd_clear_savedwrite(pmd_mk_savedwrite(pmd))));
> }
> +#endif
>
> #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
> static void __init pud_basic_tests(unsigned long pfn, pgprot_t prot)
> @@ -1005,8 +1010,10 @@ static int __init debug_vm_pgtable(void)
> pmd_huge_tests(pmdp, pmd_aligned, prot);
> pud_huge_tests(pudp, pud_aligned, prot);
>
> +#ifdef CONFIG_NUMA_BALANCING
> pte_savedwrite_tests(pte_aligned, prot);
> pmd_savedwrite_tests(pmd_aligned, prot);
> +#endif
BTW, config wrappers should be avoided at the call site. If and when needed
a stub is defined for !CONFIG_XXX_XXX.
>
> pte_unmap_unlock(ptep, ptl);
>
>
