Re: [PATCH v4 27/66] mm/mmap: Change do_brk_munmap() to use do_mas_align_munmap()

[Vlastimil Babka]

On 12/1/21 15:30, Liam Howlett wrote:
> From: "Liam R. Howlett" <Liam.Howlett@xxxxxxxxxx>
> 
> do_brk_munmap() has already aligned the address and has a maple tree
> state to be used.  Use the new do_mas_align_munmap() to avoid
> unnecessary alignment and error checks.
> 
> Signed-off-by: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx>
> ---
>  mm/mmap.c | 9 ++++++---
>  1 file changed, 6 insertions(+), 3 deletions(-)
> 
> diff --git a/mm/mmap.c b/mm/mmap.c
> index 14190306a483..79b8494d83c6 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -2926,12 +2926,15 @@ static int do_brk_munmap(struct ma_state *mas, struct vm_area_struct *vma,
>  	struct mm_struct *mm = vma->vm_mm;
>  	struct vm_area_struct unmap;
>  	unsigned long unmap_pages;
> -	int ret = 1;
> +	int ret;
>  
>  	arch_unmap(mm, newbrk, oldbrk);
>  
> -	if (likely(vma->vm_start >= newbrk)) { // remove entire mapping(s)
> -		ret = do_mas_munmap(mas, mm, newbrk, oldbrk-newbrk, uf, true);
> +	if (likely((vma->vm_end < oldbrk) ||
> +		   ((vma->vm_start == newbrk) && (vma->vm_end == oldbrk)))) {

Can you describe this change of conditions in the commit log as well?

> +		// remove entire mapping(s)
> +		ret = do_mas_align_munmap(mas, vma, mm, newbrk, oldbrk, uf,
> +					  true);
>  		goto munmap_full_vma;
>  	}
>