linux-kernel - Re: [PATCH v2 03/16] mm: add vma_desc_size(), vma_desc

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Message-ID: <afrz7upbj463hmejktsw2dxvvty7a7jtsibyn4fdlwwyrzogrh@c3svlrvl4job>
Date: Thu, 11 Sep 2025 10:36:58 +0200
From: Jan Kara <jack@...e.cz>
To: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>, 
	Jonathan Corbet <corbet@....net>, Matthew Wilcox <willy@...radead.org>, 
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	Jason Gunthorpe <jgg@...dia.com>
Subject: Re: [PATCH v2 03/16] mm: add vma_desc_size(), vma_desc_pages()
 helpers

On Wed 10-09-25 21:21:58, 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@...cle.com>

Looks good, I presume more users will come later in the series :). Feel
free to add:

Reviewed-by: Jan Kara <jack@...e.cz>

								Honza

> ---
>  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;
> +}
> +
>  /* 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;
> -- 
> 2.51.0
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR