linux-kernel - Re: [RFCv3 3/5] mm/balloon: apply mobile page migratable into balloon

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Message-ID: <559F1014.6070306@lge.com>
Date:	Fri, 10 Jul 2015 09:21:40 +0900
From:	Gioh Kim <gioh.kim@....com>
To:	"Michael S. Tsirkin" <mst@...hat.com>, koct9i@...il.com,
	aquini@...hat.com
CC:	jlayton@...chiereds.net, bfields@...ldses.org, vbabka@...e.cz,
	iamjoonsoo.kim@....com, viro@...iv.linux.org.uk,
	minchan@...nel.org, linux-fsdevel@...r.kernel.org,
	virtualization@...ts.linux-foundation.org,
	linux-kernel@...r.kernel.org, linux-api@...r.kernel.org,
	linux-mm@...ck.org, gunho.lee@....com, akpm@...ux-foundation.org,
	Gioh Kim <gurugio@...mail.net>
Subject: Re: [RFCv3 3/5] mm/balloon: apply mobile page migratable into balloon



>> @@ -124,6 +130,7 @@ static inline void balloon_page_insert(struct balloon_dev_info *balloon,
>>   				       struct page *page)
>>   {
>>   	__SetPageBalloon(page);
>> +	page->mapping = balloon->inode->i_mapping;
>>   	SetPagePrivate(page);
>>   	set_page_private(page, (unsigned long)balloon);
>>   	list_add(&page->lru, &balloon->pages);
>> @@ -140,6 +147,7 @@ static inline void balloon_page_insert(struct balloon_dev_info *balloon,
>>   static inline void balloon_page_delete(struct page *page)
>>   {
>>   	__ClearPageBalloon(page);
>> +	page->mapping = NULL;
>>   	set_page_private(page, 0);
>>   	if (PagePrivate(page)) {
>>   		ClearPagePrivate(page);
>
> Order of cleanup here is not the reverse of the order of initialization.
> Better make it exactly the reverse.
>
>
> Also, I have a question: is it enough to lock the page to make changing
> the mapping safe? Do all users lock the page too?
>
>
>
>

I think balloon developers can answer that precisely.

I've just follow this comment:
http://lxr.free-electrons.com/source/include/linux/balloon_compaction.h#L16
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