Re: [PATCH v3 14/16] mm/mmap: Use PHYS_PFN in mmap_region()

[Lorenzo Stoakes]

On Thu, Jul 04, 2024 at 02:27:16PM GMT, Liam R. Howlett wrote:
> From: "Liam R. Howlett" <Liam.Howlett@xxxxxxxxxx>
>
> Instead of shifting the length by PAGE_SIZE, use PHYS_PFN.  Also use the
> existing local variable everywhere instead of some of the time.
>
> Signed-off-by: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx>
> ---
>  mm/mmap.c | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/mm/mmap.c b/mm/mmap.c
> index 0c334eeae8cd..b14da6bd257f 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -2935,7 +2935,7 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
>  	struct mm_struct *mm = current->mm;
>  	struct vm_area_struct *vma = NULL;
>  	struct vm_area_struct *next, *prev, *merge;
> -	pgoff_t pglen = len >> PAGE_SHIFT;
> +	pgoff_t pglen = PHYS_PFN(len);
>  	unsigned long charged = 0;
>  	struct vma_munmap_struct vms;
>  	struct ma_state mas_detach;
> @@ -2955,7 +2955,7 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
>  	 * MAP_FIXED may remove pages of mappings that intersects with requested
>  	 * mapping. Account for the pages it would unmap.
>  	 */
> -	if (!may_expand_vm(mm, vm_flags, (len >> PAGE_SHIFT) - nr_pages))
> +	if (!may_expand_vm(mm, vm_flags, pglen - nr_pages))
>  		return -ENOMEM;
>
>  	if (unlikely(!can_modify_mm(mm, addr, end)))
> @@ -2990,7 +2990,7 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
>  	 * Private writable mapping: check memory availability
>  	 */
>  	if (accountable_mapping(file, vm_flags)) {
> -		charged = len >> PAGE_SHIFT;
> +		charged = pglen;
>  		charged -= nr_accounted;
>  		if (security_vm_enough_memory_mm(mm, charged))
>  			goto abort_munmap;
> @@ -3149,14 +3149,14 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
>  	if (vms.nr_pages)
>  		vms_complete_munmap_vmas(&vms, &mas_detach);
>
> -	vm_stat_account(mm, vm_flags, len >> PAGE_SHIFT);
> +	vm_stat_account(mm, vm_flags, pglen);
>  	if (vm_flags & VM_LOCKED) {
>  		if ((vm_flags & VM_SPECIAL) || vma_is_dax(vma) ||
>  					is_vm_hugetlb_page(vma) ||
>  					vma == get_gate_vma(current->mm))
>  			vm_flags_clear(vma, VM_LOCKED_MASK);
>  		else
> -			mm->locked_vm += (len >> PAGE_SHIFT);
> +			mm->locked_vm += pglen;
>  	}
>
>  	if (file)
> --
> 2.43.0
>

Maybe I should literally look ahead before making comments :)) thanks for
reading my mind and doing what I asked though! ;)

However I don't think you've fixed the duplication of PHYS_PFN(vm_end -
vm_start) in count_vma_pages_range() - still worth doing I think.

Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@xxxxxxxxxx>