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

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Date:	Thu, 08 Mar 2012 15:50:58 +0800
From:	Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
CC:	Stephen Rothwell <sfr@...b.auug.org.au>,
	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

On 03/08/2012 03:50 PM, Andrew Morton wrote:

> On Thu, 8 Mar 2012 18:41:05 +1100 Stephen Rothwell <sfr@...b.auug.org.au> wrote:
> 
>> 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.
> 
> Doh.  The author reviewed that for me too!
> 
> I'll drop it - please rework, retest and resend?


I am sorry, i will repost it!

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