On 09/08/2023 07:11, Yin Fengwei wrote:
> It will be used to check whether the folio is mapped to specific
> VMA and whether the mapping address of folio is in the range.
>
> Also a helper function folio_within_vma() to check whether folio
> is in the range of vma based on folio_in_range().
>
> Signed-off-by: Yin Fengwei <fengwei.yin@xxxxxxxxx>
> ---
> mm/internal.h | 35 +++++++++++++++++++++++++++++++++++
> 1 file changed, 35 insertions(+)
>
> diff --git a/mm/internal.h b/mm/internal.h
> index 154da4f0d557..5d1b71010fd2 100644
> --- a/mm/internal.h
> +++ b/mm/internal.h
> @@ -585,6 +585,41 @@ extern long faultin_vma_page_range(struct vm_area_struct *vma,
> bool write, int *locked);
> extern bool mlock_future_ok(struct mm_struct *mm, unsigned long flags,
> unsigned long bytes);
> +
> +static inline bool
> +folio_in_range(struct folio *folio, struct vm_area_struct *vma,
> + unsigned long start, unsigned long end)
I still think it would be beneficial to have a comment block describing the
requirements and behaviour of the function:
- folio must have at least 1 page that is mapped in vma
- the result tells you if the folio lies within the range, but it does not tell
you that all of its pages are actually _mapped_ (e.g. they may not have been
faulted in yet).
- I think [start, end) is intended intersect with the vma too? (although I'm
pretty sure sure the logic works if it doesn't?)
> +{
> + pgoff_t pgoff, addr;
> + unsigned long vma_pglen = (vma->vm_end - vma->vm_start) >> PAGE_SHIFT;
> +
> + VM_WARN_ON_FOLIO(folio_test_ksm(folio), folio);
> + if (start > end)
> + return false;
> +
> + if (start < vma->vm_start)
> + start = vma->vm_start;
> +
> + if (end > vma->vm_end)
> + end = vma->vm_end;
> +
> + pgoff = folio_pgoff(folio);
> +
> + /* if folio start address is not in vma range */
> + if (!in_range(pgoff, vma->vm_pgoff, vma_pglen))
> + return false;
> +
> + addr = vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT);
> +
> + return !(addr < start || end - addr < folio_size(folio));
> +}
> +
> +static inline bool
> +folio_within_vma(struct folio *folio, struct vm_area_struct *vma)
why call this *within* but call the folio_in_range() *in*? Feels cleaner to use
the same word for both.
> +{
> + return folio_in_range(folio, vma, vma->vm_start, vma->vm_end);
> +}
> +
> /*
> * mlock_vma_folio() and munlock_vma_folio():
> * should be called with vma's mmap_lock held for read or write,
