On 2022/3/1 7:57, Yang Shi wrote:
> The hugepage_vma_check() called by khugepaged_enter_vma_merge() does
> check VM_NO_KHUGEPAGED. Remove the check from caller and move the check
> in hugepage_vma_check() up.
>
> More checks may be run for VM_NO_KHUGEPAGED vmas, but MADV_HUGEPAGE is
> definitely not a hot path, so cleaner code does outweigh.
>
> Signed-off-by: Yang Shi <shy828301@xxxxxxxxx>
> ---
> mm/khugepaged.c | 9 ++++++---
> 1 file changed, 6 insertions(+), 3 deletions(-)
>
> diff --git a/mm/khugepaged.c b/mm/khugepaged.c
> index 131492fd1148..82c71c6da9ce 100644
> --- a/mm/khugepaged.c
> +++ b/mm/khugepaged.c
> @@ -366,8 +366,7 @@ int hugepage_madvise(struct vm_area_struct *vma,
> * register it here without waiting a page fault that
> * may not happen any time soon.
> */
> - if (!(*vm_flags & VM_NO_KHUGEPAGED) &&
> - khugepaged_enter_vma_merge(vma, *vm_flags))
> + if (khugepaged_enter_vma_merge(vma, *vm_flags))
> return -ENOMEM;
> break;
> case MADV_NOHUGEPAGE:
> @@ -446,6 +445,9 @@ static bool hugepage_vma_check(struct vm_area_struct *vma,
> if (!transhuge_vma_enabled(vma, vm_flags))
> return false;
>
> + if (vm_flags & VM_NO_KHUGEPAGED)
> + return false;
> +
This patch does improve the readability. But I have a question.
It seems VM_NO_KHUGEPAGED is not checked in the below if-condition:
/* Only regular file is valid */
if (IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS) && vma->vm_file &&
(vm_flags & VM_EXEC)) {
struct inode *inode = vma->vm_file->f_inode;
return !inode_is_open_for_write(inode) &&
S_ISREG(inode->i_mode);
}
If we return false due to VM_NO_KHUGEPAGED here, it seems it will affect the
return value of this CONFIG_READ_ONLY_THP_FOR_FS condition check.
Or am I miss something?
Thanks.
> if (vma->vm_file && !IS_ALIGNED((vma->vm_start >> PAGE_SHIFT) -
> vma->vm_pgoff, HPAGE_PMD_NR))
> return false;
> @@ -471,7 +473,8 @@ static bool hugepage_vma_check(struct vm_area_struct *vma,
> return false;
> if (vma_is_temporary_stack(vma))
> return false;
> - return !(vm_flags & VM_NO_KHUGEPAGED);
> +
> + return true;
> }
>
> int __khugepaged_enter(struct mm_struct *mm)
>
