linux-kernel - Re: [PATCH v3 10/16] zsmalloc: factor page chain functionality out

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Date:	Tue, 19 Apr 2016 16:46:15 +0900
From:	Minchan Kim <minchan@...nel.org>
To:	Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	<linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>,
	<jlayton@...chiereds.net>, <bfields@...ldses.org>,
	Vlastimil Babka <vbabka@...e.cz>,
	Joonsoo Kim <iamjoonsoo.kim@....com>, <koct9i@...il.com>,
	<aquini@...hat.com>, <virtualization@...ts.linux-foundation.org>,
	Mel Gorman <mgorman@...e.de>, Hugh Dickins <hughd@...gle.com>,
	Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
	Rik van Riel <riel@...hat.com>, <rknize@...orola.com>,
	Gioh Kim <gi-oh.kim@...fitbricks.com>,
	Sangseok Lee <sangseok.lee@....com>,
	Chan Gyun Jeong <chan.jeong@....com>,
	Al Viro <viro@...IV.linux.org.uk>,
	YiPing Xu <xuyiping@...ilicon.com>
Subject: Re: [PATCH v3 10/16] zsmalloc: factor page chain functionality out

On Mon, Apr 18, 2016 at 09:33:05AM +0900, Sergey Senozhatsky wrote:
> Hello,
> 
> On (03/30/16 16:12), Minchan Kim wrote:
> > @@ -1421,7 +1434,6 @@ static unsigned long obj_malloc(struct size_class *class,
> >  	unsigned long m_offset;
> >  	void *vaddr;
> >  
> > -	handle |= OBJ_ALLOCATED_TAG;
> 
> a nitpick, why did you replace this ALLOCATED_TAG assignment
> with 2 'handle | OBJ_ALLOCATED_TAG'?

I thought this handle variable in here is pure handle but OBJ_ALLOCATED_TAG
should live in head(i.e., link->handle), not pure handle, itself.

> 
> 	-ss
> 
> >  	obj = get_freeobj(first_page);
> >  	objidx_to_page_and_offset(class, first_page, obj,
> >  				&m_page, &m_offset);
> > @@ -1431,10 +1443,10 @@ static unsigned long obj_malloc(struct size_class *class,
> >  	set_freeobj(first_page, link->next >> OBJ_ALLOCATED_TAG);
> >  	if (!class->huge)
> >  		/* record handle in the header of allocated chunk */
> > -		link->handle = handle;
> > +		link->handle = handle | OBJ_ALLOCATED_TAG;
> >  	else
> >  		/* record handle in first_page->private */
> > -		set_page_private(first_page, handle);
> > +		set_page_private(first_page, handle | OBJ_ALLOCATED_TAG);
> >  	kunmap_atomic(vaddr);
> >  	mod_zspage_inuse(first_page, 1);
> >  	zs_stat_inc(class, OBJ_USED, 1);