Re: [PATCH v2 03/16] mm: add vma_desc_size(), vma_desc_pages() helpers

[David Hildenbrand <david@xxxxxxxxxx>]

On 10.09.25 22:21, Lorenzo Stoakes wrote:
> It's useful to be able to determine the size of a VMA descriptor range used
> on f_op->mmap_prepare, expressed both in bytes and pages, so add helpers
> for both and update code that could make use of it to do so.
>
> Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@xxxxxxxxxx>
> ---
>   fs/ntfs3/file.c    |  2 +-
>   include/linux/mm.h | 10 ++++++++++
>   mm/secretmem.c     |  2 +-
>   3 files changed, 12 insertions(+), 2 deletions(-)
>
> diff --git a/fs/ntfs3/file.c b/fs/ntfs3/file.c
> index c1ece707b195..86eb88f62714 100644
> --- a/fs/ntfs3/file.c
> +++ b/fs/ntfs3/file.c
> @@ -304,7 +304,7 @@ static int ntfs_file_mmap_prepare(struct vm_area_desc *desc)
>   
>   	if (rw) {
>   		u64 to = min_t(loff_t, i_size_read(inode),
> -			       from + desc->end - desc->start);
> +			       from + vma_desc_size(desc));
>   
>   		if (is_sparsed(ni)) {
>   			/* Allocate clusters for rw map. */
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 892fe5dbf9de..0b97589aec6d 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -3572,6 +3572,16 @@ static inline unsigned long vma_pages(const struct vm_area_struct *vma)
>   	return (vma->vm_end - vma->vm_start) >> PAGE_SHIFT;
>   }
>   
> +static inline unsigned long vma_desc_size(struct vm_area_desc *desc)
> +{
> +	return desc->end - desc->start;
> +}
> +
> +static inline unsigned long vma_desc_pages(struct vm_area_desc *desc)
> +{
> +	return vma_desc_size(desc) >> PAGE_SHIFT;
> +}

Should parameters in both functions be const * ?

> +
>   /* Look up the first VMA which exactly match the interval vm_start ... vm_end */
>   static inline struct vm_area_struct *find_exact_vma(struct mm_struct *mm,
>   				unsigned long vm_start, unsigned long vm_end)
> diff --git a/mm/secretmem.c b/mm/secretmem.c
> index 60137305bc20..62066ddb1e9c 100644
> --- a/mm/secretmem.c
> +++ b/mm/secretmem.c
> @@ -120,7 +120,7 @@ static int secretmem_release(struct inode *inode, struct file *file)
>   
>   static int secretmem_mmap_prepare(struct vm_area_desc *desc)
>   {
> -	const unsigned long len = desc->end - desc->start;
> +	const unsigned long len = vma_desc_size(desc);
>   
>   	if ((desc->vm_flags & (VM_SHARED | VM_MAYSHARE)) == 0)
>   		return -EINVAL;

Acked-by: David Hildenbrand <david@xxxxxxxxxx>

--
Cheers

David / dhildenb