linux-kernel - Re: [PATCH v2 09/20] mm, hugetlb: protect region tracking via newly introduced resv

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Date:	Thu, 22 Aug 2013 15:59:19 +0900
From:	Joonsoo Kim <iamjoonsoo.kim@....com>
To:	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Rik van Riel <riel@...hat.com>, Mel Gorman <mgorman@...e.de>,
	Michal Hocko <mhocko@...e.cz>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Hugh Dickins <hughd@...gle.com>,
	Davidlohr Bueso <davidlohr.bueso@...com>,
	David Gibson <david@...son.dropbear.id.au>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	Wanpeng Li <liwanp@...ux.vnet.ibm.com>,
	Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
	Hillf Danton <dhillf@...il.com>
Subject: Re: [PATCH v2 09/20] mm, hugetlb: protect region tracking via newly
 introduced resv_map lock

On Wed, Aug 21, 2013 at 03:43:27PM +0530, Aneesh Kumar K.V wrote:

> >  static long region_chg(struct resv_map *resv, long f, long t)
> >  {
> >  	struct list_head *head = &resv->regions;
> > -	struct file_region *rg, *nrg;
> > +	struct file_region *rg, *nrg = NULL;
> >  	long chg = 0;
> >
> > +retry:
> > +	spin_lock(&resv->lock);
> >  	/* Locate the region we are before or in. */
> >  	list_for_each_entry(rg, head, link)
> >  		if (f <= rg->to)
> > @@ -202,15 +199,27 @@ static long region_chg(struct resv_map *resv, long f, long t)
> >  	 * Subtle, allocate a new region at the position but make it zero
> >  	 * size such that we can guarantee to record the reservation. */
> >  	if (&rg->link == head || t < rg->from) {
> > -		nrg = kmalloc(sizeof(*nrg), GFP_KERNEL);
> > -		if (!nrg)
> > -			return -ENOMEM;
> > +		if (!nrg) {
> > +			nrg = kmalloc(sizeof(*nrg), GFP_NOWAIT);
> 
> Do we really need to have the GFP_NOWAIT allocation attempt. Why can't we simply say
> allocate and retry ? Or should resv->lock be a mutex ?
> 

Yes, your proposal that simply allocate and retry looks good to me.
I will change it.

Thanks.
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