linux-kernel - Re: linux-next: manual merge of the akpm tree with Linus' tree

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Date:	Thu, 8 Mar 2012 18:41:05 +1100
From:	Stephen Rothwell <sfr@...b.auug.org.au>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	linux-next@...r.kernel.org, linux-kernel@...r.kernel.org,
	Linus <torvalds@...ux-foundation.org>
Subject: Re: linux-next: manual merge of the akpm tree with Linus' tree

Hi Andrew,

On Wed, 7 Mar 2012 23:32:20 -0800 Andrew Morton <akpm@...ux-foundation.org> wrote:
>
> Actually they're different.  I reworked the earlier patch as below.

OK.  But some comments.

> diff -puN arch/x86/mm/hugetlbpage.c~hugetlb-drop-prev_vma-in-hugetlb_get_unmapped_area_topdown arch/x86/mm/hugetlbpage.c
> --- a/arch/x86/mm/hugetlbpage.c~hugetlb-drop-prev_vma-in-hugetlb_get_unmapped_area_topdown
> +++ a/arch/x86/mm/hugetlbpage.c
> @@ -308,7 +308,7 @@ static unsigned long hugetlb_get_unmappe
>  {
>  	struct hstate *h = hstate_file(file);
>  	struct mm_struct *mm = current->mm;
> -	struct vm_area_struct *vma, *prev_vma;
> +	struct vm_area_struct *vma;

You still remove prev_vma ...

>  	unsigned long base = mm->mmap_base, addr = addr0;
>  	unsigned long largest_hole = mm->cached_hole_size;
>  	int first_time = 1;
> @@ -334,25 +334,16 @@ try_again:
>  		 * i.e. return with success:
>  		 */
>  		vma = find_vma(mm, addr);
> -		if (!vma)
> -			return addr;
> -
> -		/*
> -		 * new region fits between prev_vma->vm_end and
> -		 * vma->vm_start, use it:
> -		 */
> -		prev_vma = vma->vm_prev;
> -		if (addr + len <= vma->vm_start &&
> -		            (!prev_vma || (addr >= prev_vma->vm_end))) {
> +		if (vma)
> +			prev_vma = vma->vm_prev;

But then assign to it ...

> +		if (!vma || addr + len <= vma->vm_start) {
>  			/* remember the address as a hint for next time */
>  		        mm->cached_hole_size = largest_hole;
>  		        return (mm->free_area_cache = addr);
> -		} else {
> +		} else if (mm->free_area_cache == vma->vm_end) {
>  			/* pull free_area_cache down to the first hole */
> -		        if (mm->free_area_cache == vma->vm_end) {
> -				mm->free_area_cache = vma->vm_start;
> -				mm->cached_hole_size = largest_hole;
> -			}
> +			mm->free_area_cache = vma->vm_start;
> +			mm->cached_hole_size = largest_hole;
>  		}
>  
>  		/* remember the largest hole we saw so far */

But it never gets used.

-- 
Cheers,
Stephen Rothwell                    sfr@...b.auug.org.au

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