linux-kernel - Re: [PATCH] mm/mmap: introduce vma_range

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Message-ID: <20240122220031.pwiravglee7o7k34@revolver>
Date: Mon, 22 Jan 2024 17:00:31 -0500
From: "Liam R. Howlett" <Liam.Howlett@...cle.com>
To: Yajun Deng <yajun.deng@...ux.dev>
Cc: akpm@...ux-foundation.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm/mmap: introduce vma_range_init()

* Yajun Deng <yajun.deng@...ux.dev> [240110 21:15]:
> There is a lot of code needs to set the range of vma, introduce
> vma_range_init() to initialize the range of vma.
> 
> Signed-off-by: Yajun Deng <yajun.deng@...ux.dev>
> ---
>  include/linux/mm.h |  9 +++++++++
>  mm/mmap.c          | 29 +++++++----------------------
>  2 files changed, 16 insertions(+), 22 deletions(-)

This isn't a whole lot of code, are there others?  We're losing code
clarity in favour of saving 6 lines?

> 
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index f5a97dec5169..abb4534be3cc 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -3516,6 +3516,15 @@ static inline bool range_in_vma(struct vm_area_struct *vma,
>  	return (vma && vma->vm_start <= start && end <= vma->vm_end);
>  }
>  
> +static inline void vma_range_init(struct vm_area_struct *vma,

Any reason this can't be in mm/internal.h ?

vma_range_set(), vma_set_range(), or just vma_range() might be a better
name?  My thinking is that some of these are actually modifying the vma
and not just initializing it, right?

> +				  unsigned long start, unsigned long end,
> +				  pgoff_t pgoff)
> +{
> +	vma->vm_start = start;
> +	vma->vm_end = end;
> +	vma->vm_pgoff = pgoff;
> +}
> +
>  #ifdef CONFIG_MMU
>  pgprot_t vm_get_page_prot(unsigned long vm_flags);
>  void vma_set_page_prot(struct vm_area_struct *vma);
> diff --git a/mm/mmap.c b/mm/mmap.c
> index 06f1f3e88598..0d3f4612d001 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -663,9 +663,7 @@ int vma_expand(struct vma_iterator *vmi, struct vm_area_struct *vma,
>  
>  	vma_prepare(&vp);
>  	vma_adjust_trans_huge(vma, start, end, 0);
> -	vma->vm_start = start;
> -	vma->vm_end = end;
> -	vma->vm_pgoff = pgoff;
> +	vma_range_init(vma, start, end, pgoff);
>  	vma_iter_store(vmi, vma);
>  
>  	vma_complete(&vp, vmi, vma->vm_mm);
> @@ -708,9 +706,7 @@ int vma_shrink(struct vma_iterator *vmi, struct vm_area_struct *vma,
>  	vma_adjust_trans_huge(vma, start, end, 0);
>  
>  	vma_iter_clear(vmi);
> -	vma->vm_start = start;
> -	vma->vm_end = end;
> -	vma->vm_pgoff = pgoff;
> +	vma_range_init(vma, start, end, pgoff);
>  	vma_complete(&vp, vmi, vma->vm_mm);
>  	return 0;
>  }
> @@ -1015,10 +1011,7 @@ static struct vm_area_struct
>  
>  	vma_prepare(&vp);
>  	vma_adjust_trans_huge(vma, vma_start, vma_end, adj_start);
> -
> -	vma->vm_start = vma_start;
> -	vma->vm_end = vma_end;
> -	vma->vm_pgoff = vma_pgoff;
> +	vma_range_init(vma, vma_start, vma_end, vma_pgoff);
>  
>  	if (vma_expanded)
>  		vma_iter_store(vmi, vma);
> @@ -2811,11 +2804,9 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
>  	}
>  
>  	vma_iter_config(&vmi, addr, end);
> -	vma->vm_start = addr;
> -	vma->vm_end = end;
> +	vma_range_init(vma, addr, end, pgoff);
>  	vm_flags_init(vma, vm_flags);
>  	vma->vm_page_prot = vm_get_page_prot(vm_flags);
> -	vma->vm_pgoff = pgoff;
>  
>  	if (file) {
>  		vma->vm_file = get_file(file);
> @@ -3165,9 +3156,7 @@ static int do_brk_flags(struct vma_iterator *vmi, struct vm_area_struct *vma,
>  		goto unacct_fail;
>  
>  	vma_set_anonymous(vma);
> -	vma->vm_start = addr;
> -	vma->vm_end = addr + len;
> -	vma->vm_pgoff = addr >> PAGE_SHIFT;
> +	vma_range_init(vma, addr, addr + len, addr >> PAGE_SHIFT);
>  	vm_flags_init(vma, flags);
>  	vma->vm_page_prot = vm_get_page_prot(flags);
>  	vma_start_write(vma);
> @@ -3404,9 +3393,7 @@ struct vm_area_struct *copy_vma(struct vm_area_struct **vmap,
>  		new_vma = vm_area_dup(vma);
>  		if (!new_vma)
>  			goto out;
> -		new_vma->vm_start = addr;
> -		new_vma->vm_end = addr + len;
> -		new_vma->vm_pgoff = pgoff;
> +		vma_range_init(new_vma, addr, addr + len, pgoff);
>  		if (vma_dup_policy(vma, new_vma))
>  			goto out_free_vma;
>  		if (anon_vma_clone(new_vma, vma))
> @@ -3574,9 +3561,7 @@ static struct vm_area_struct *__install_special_mapping(
>  	if (unlikely(vma == NULL))
>  		return ERR_PTR(-ENOMEM);
>  
> -	vma->vm_start = addr;
> -	vma->vm_end = addr + len;
> -
> +	vma_range_init(vma, addr, addr + len, 0);
>  	vm_flags_init(vma, (vm_flags | mm->def_flags |
>  		      VM_DONTEXPAND | VM_SOFTDIRTY) & ~VM_LOCKED_MASK);
>  	vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
> -- 
> 2.25.1
> 
>