linux-kernel - Re: [PATCH] mempolicy: refix mbind

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Message-ID: <4EF0D1A3.7010700@gmail.com>
Date:	Tue, 20 Dec 2011 13:19:15 -0500
From:	KOSAKI Motohiro <kosaki.motohiro@...il.com>
To:	Johannes Weiner <hannes@...xchg.org>
CC:	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Minchan Kim <minchan.kim@...il.com>,
	Caspar Zhang <caspar@...parzhang.com>
Subject: Re: [PATCH] mempolicy: refix mbind_range() vma issue

>> +		pgoff = vma->vm_pgoff + ((vmstart - vma->vm_start)>>  PAGE_SHIFT);
>>   		prev = vma_merge(mm, prev, vmstart, vmend, vma->vm_flags,
>> -				  vma->anon_vma, vma->vm_file, vma->vm_pgoff,
>> +				  vma->anon_vma, vma->vm_file, pgoff,
>>   				  new_pol);
>>   		if (prev) {
>>   			vma = prev;
>
> This is essentially a revert of the aforementioned commit.
>
> What you added instead is the fixing of @prev: only when mbind is
> vma-aligned can the new area be potentially merged into the preceding
> one.  Otherwise that original vma is the one we need to check for
> compatibility with the mbind range and leave the original prev alone:
>
> 	[prev         ][vma            ]
> 	                    |start
>
> 	[prev         ][vma][mbind vma ]
>
> This should NOT attempt to merge mbind vma with prev (and forget about
> and leak vma, iirc), but check if vma and the mbind vma are compatible
> or should be separate areas.
>
> Could you please add something to that extent to the changelog?

When making new test case, I've found one bug in my patch. So, I've
sent new patch w/ detailed bug explanaion. :)

Thanks.


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