linux-kernel - Re: [PATCH 1/1] pagemap clear_refs: modify to specify anon or mapped vma clearing

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Date:	Fri, 24 Jul 2009 16:39:26 +0800
From:	Amerigo Wang <xiyou.wangcong@...il.com>
To:	"Moussa A. Ba" <moussa.a.ba@...il.com>
Cc:	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
	adobriyan@...il.com, mpm@...enic.com, mel@....ul.ie,
	yinghan@...gle.com, npiggin@...e.de, jaredeh@...il.com
Subject: Re: [PATCH 1/1] pagemap clear_refs: modify to specify anon or
	mapped vma clearing

On Thu, Jul 23, 2009 at 08:57:22PM -0700, Moussa A. Ba wrote:
>
> Signed-off-by: Jared E. Hulbert <jaredeh@...il.com>
> Signed-off-by: Moussa Ba <moussa.a.ba@...il.com>
> --- a/fs/proc/task_mmu.c	2009-07-21 14:30:01.000000000 -0700
> +++ b/fs/proc/task_mmu.c	2009-07-21 14:32:56.000000000 -0700
> @@ -461,6 +461,33 @@
>  	cond_resched();
>  	return 0;
>  }
> +static void walk_vma_area(struct mm_walk *this_walk, struct  
> vm_area_struct *vma,
> +						int type)
> +{
> +	switch (type) {
> +		/* Clear Anon VMAs only */
> +	case 1:
> +		if (!is_vm_hugetlb_page(vma) && !vma->vm_file)
> +			walk_page_range(vma->vm_start,
> +					vma->vm_end,
> +					this_walk);
> +		break;
> +		/* Clear Mapped VMAs only */
> +	case 2:
> +		if (!is_vm_hugetlb_page(vma) && vma->vm_file)
> +			walk_page_range(vma->vm_start,
> +					vma->vm_end,
> +					this_walk);
> +		break;
> +		/* Clear All VMAs */
> +	default:
> +		if (!is_vm_hugetlb_page(vma))
> +			walk_page_range(vma->vm_start,
> +					vma->vm_end,
> +					this_walk);
> +		break;
> +	}
> +}
>


First, can you make these plain numbers as macros or enum types?

Second, I believe the above code can be simiplified, how about below?

{
    if (!is_vm_hugetlb_page(vma)) {
        if (type == 1 && vma->vm_file)
             return;
        if (type == 2 && !vma->vm_file)
             return;
        walk_page_range(vma->vm_start, vma->end, this_walk);
    }
}



>  static ssize_t clear_refs_write(struct file *file, const char __user *  
> buf,
>  				size_t count, loff_t * ppos)
> @@ -469,13 +496,15 @@
>  	char buffer[PROC_NUMBUF], *end;
>  	struct mm_struct *mm;
>  	struct vm_area_struct *vma;
> +	int type;
>
>  	memset(buffer, 0, sizeof(buffer));
>  	if (count > sizeof(buffer) - 1)
>  		count = sizeof(buffer) - 1;
>  	if (copy_from_user(buffer, buf, count))
>  		return -EFAULT;
> -	if (!simple_strtol(buffer, &end, 0))
> +	type = simple_strtol(buffer, &end, 0);
> +	if (!type)
>  		return -EINVAL;
>  	if (*end == '\n')
>  		end++;
> @@ -491,9 +520,7 @@
>  		down_read(&mm->mmap_sem);
>  		for (vma = mm->mmap; vma; vma = vma->vm_next) {
>  			clear_refs_walk.private = vma;
> -			if (!is_vm_hugetlb_page(vma))
> -				walk_page_range(vma->vm_start, vma->vm_end,
> -						&clear_refs_walk);
> +			walk_vma_area(&clear_refs_walk, vma, type);
>  		}
>  		flush_tlb_mm(mm);
>  		up_read(&mm->mmap_sem);
> --
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