Re: [PATCH v3 3/5] mm/huge_memory.c: add missing read-only THP checking in transparent_hugepage_enabled()

[Miaohe Lin]

On 2021/5/14 5:30, Yang Shi wrote:
> On Tue, May 11, 2021 at 6:49 AM Miaohe Lin <linmiaohe@xxxxxxxxxx> wrote:
>>
>> Since commit 99cb0dbd47a1 ("mm,thp: add read-only THP support for
>> (non-shmem) FS"), read-only THP file mapping is supported. But it
>> forgot to add checking for it in transparent_hugepage_enabled().
>> To fix it, we add checking for read-only THP file mapping and also
>> introduce helper transhuge_vma_enabled() to check whether thp is
>> enabled for specified vma to reduce duplicated code. We rename
>> transparent_hugepage_enabled to transparent_hugepage_active to make
>> the code easier to follow as suggested by David Hildenbrand.
>>
>> Fixes: 99cb0dbd47a1 ("mm,thp: add read-only THP support for (non-shmem) FS")
>> Signed-off-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>
> 
> Looks correct to me. Reviewed-by: Yang Shi <shy828301@xxxxxxxxx>
> 

Many thanks for your Reviewed-by tag.

> Just a nit below:
> 
>> ---
>>  fs/proc/task_mmu.c      |  2 +-
>>  include/linux/huge_mm.h | 27 ++++++++++++++++++++-------
>>  mm/huge_memory.c        | 11 ++++++++++-
>>  mm/khugepaged.c         |  4 +---
>>  mm/shmem.c              |  3 +--
>>  5 files changed, 33 insertions(+), 14 deletions(-)
>>
>> diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
>> index fc9784544b24..7389df326edd 100644
>> --- a/fs/proc/task_mmu.c
>> +++ b/fs/proc/task_mmu.c
>> @@ -832,7 +832,7 @@ static int show_smap(struct seq_file *m, void *v)
>>         __show_smap(m, &mss, false);
>>
>>         seq_printf(m, "THPeligible:    %d\n",
>> -                  transparent_hugepage_enabled(vma));
>> +                  transparent_hugepage_active(vma));
>>
>>         if (arch_pkeys_enabled())
>>                 seq_printf(m, "ProtectionKey:  %8u\n", vma_pkey(vma));
>> diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
>> index 0a526f211fec..a35c13d1f487 100644
>> --- a/include/linux/huge_mm.h
>> +++ b/include/linux/huge_mm.h
>> @@ -115,9 +115,19 @@ extern struct kobj_attribute shmem_enabled_attr;
>>
>>  extern unsigned long transparent_hugepage_flags;
>>
>> +static inline bool transhuge_vma_enabled(struct vm_area_struct *vma,
> 
> I'd like to have this function defined next to transhuge_vma_suitable().
> 

Sounds reasonable. Will do. Thanks!

>> +                                         unsigned long vm_flags)
>> +{
>> +       /* Explicitly disabled through madvise. */
>> +       if ((vm_flags & VM_NOHUGEPAGE) ||
>> +           test_bit(MMF_DISABLE_THP, &vma->vm_mm->flags))
>> +               return false;
>> +       return true;
>> +}
>> +
>>  /*
>>   * to be used on vmas which are known to support THP.
>> - * Use transparent_hugepage_enabled otherwise
>> + * Use transparent_hugepage_active otherwise
>>   */
>>  static inline bool __transparent_hugepage_enabled(struct vm_area_struct *vma)
>>  {
>> @@ -128,15 +138,12 @@ static inline bool __transparent_hugepage_enabled(struct vm_area_struct *vma)
>>         if (transparent_hugepage_flags & (1 << TRANSPARENT_HUGEPAGE_NEVER_DAX))
>>                 return false;
>>
>> -       if (vma->vm_flags & VM_NOHUGEPAGE)
>> +       if (!transhuge_vma_enabled(vma, vma->vm_flags))
>>                 return false;
>>
>>         if (vma_is_temporary_stack(vma))
>>                 return false;
>>
>> -       if (test_bit(MMF_DISABLE_THP, &vma->vm_mm->flags))
>> -               return false;
>> -
>>         if (transparent_hugepage_flags & (1 << TRANSPARENT_HUGEPAGE_FLAG))
>>                 return true;
>>
>> @@ -150,7 +157,7 @@ static inline bool __transparent_hugepage_enabled(struct vm_area_struct *vma)
>>         return false;
>>  }
>>
>> -bool transparent_hugepage_enabled(struct vm_area_struct *vma);
>> +bool transparent_hugepage_active(struct vm_area_struct *vma);
>>
>>  static inline bool transhuge_vma_suitable(struct vm_area_struct *vma,
>>                 unsigned long haddr)
>> @@ -351,7 +358,7 @@ static inline bool __transparent_hugepage_enabled(struct vm_area_struct *vma)
>>         return false;
>>  }
>>
>> -static inline bool transparent_hugepage_enabled(struct vm_area_struct *vma)
>> +static inline bool transparent_hugepage_active(struct vm_area_struct *vma)
>>  {
>>         return false;
>>  }
>> @@ -362,6 +369,12 @@ static inline bool transhuge_vma_suitable(struct vm_area_struct *vma,
>>         return false;
>>  }
>>
>> +static inline bool transhuge_vma_enabled(struct vm_area_struct *vma,
>> +                                         unsigned long vm_flags)
>> +{
>> +       return false;
>> +}
>> +
>>  static inline void prep_transhuge_page(struct page *page) {}
>>
>>  static inline bool is_transparent_hugepage(struct page *page)
>> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
>> index 76ca1eb2a223..4f37867eed12 100644
>> --- a/mm/huge_memory.c
>> +++ b/mm/huge_memory.c
>> @@ -63,7 +63,14 @@ static struct shrinker deferred_split_shrinker;
>>  static atomic_t huge_zero_refcount;
>>  struct page *huge_zero_page __read_mostly;
>>
>> -bool transparent_hugepage_enabled(struct vm_area_struct *vma)
>> +static inline bool file_thp_enabled(struct vm_area_struct *vma)
>> +{
>> +       return transhuge_vma_enabled(vma, vma->vm_flags) && vma->vm_file &&
>> +              !inode_is_open_for_write(vma->vm_file->f_inode) &&
>> +              (vma->vm_flags & VM_EXEC);
>> +}
>> +
>> +bool transparent_hugepage_active(struct vm_area_struct *vma)
>>  {
>>         /* The addr is used to check if the vma size fits */
>>         unsigned long addr = (vma->vm_end & HPAGE_PMD_MASK) - HPAGE_PMD_SIZE;
>> @@ -74,6 +81,8 @@ bool transparent_hugepage_enabled(struct vm_area_struct *vma)
>>                 return __transparent_hugepage_enabled(vma);
>>         if (vma_is_shmem(vma))
>>                 return shmem_huge_enabled(vma);
>> +       if (IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS))
>> +               return file_thp_enabled(vma);
>>
>>         return false;
>>  }
>> diff --git a/mm/khugepaged.c b/mm/khugepaged.c
>> index 6c0185fdd815..d97b20fad6e8 100644
>> --- a/mm/khugepaged.c
>> +++ b/mm/khugepaged.c
>> @@ -442,9 +442,7 @@ static inline int khugepaged_test_exit(struct mm_struct *mm)
>>  static bool hugepage_vma_check(struct vm_area_struct *vma,
>>                                unsigned long vm_flags)
>>  {
>> -       /* Explicitly disabled through madvise. */
>> -       if ((vm_flags & VM_NOHUGEPAGE) ||
>> -           test_bit(MMF_DISABLE_THP, &vma->vm_mm->flags))
>> +       if (!transhuge_vma_enabled(vma, vm_flags))
>>                 return false;
>>
>>         /* Enabled via shmem mount options or sysfs settings. */
>> diff --git a/mm/shmem.c b/mm/shmem.c
>> index a08cedefbfaa..1dcbec313c70 100644
>> --- a/mm/shmem.c
>> +++ b/mm/shmem.c
>> @@ -4032,8 +4032,7 @@ bool shmem_huge_enabled(struct vm_area_struct *vma)
>>         loff_t i_size;
>>         pgoff_t off;
>>
>> -       if ((vma->vm_flags & VM_NOHUGEPAGE) ||
>> -           test_bit(MMF_DISABLE_THP, &vma->vm_mm->flags))
>> +       if (!transhuge_vma_enabled(vma, vma->vm_flags))
>>                 return false;
>>         if (shmem_huge == SHMEM_HUGE_FORCE)
>>                 return true;
>> --
>> 2.23.0
>>
>>
> .
>