From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx195.postini.com [74.125.245.195]) by kanga.kvack.org (Postfix) with SMTP id 271DB6B0031 for ; Tue, 30 Jul 2013 22:27:53 -0400 (EDT) Date: Wed, 31 Jul 2013 11:27:51 +0900 From: Joonsoo Kim Subject: Re: [PATCH 01/18] mm, hugetlb: protect reserved pages when softofflining requests the pages Message-ID: <20130731022751.GA2548@lge.com> References: <1375075929-6119-1-git-send-email-iamjoonsoo.kim@lge.com> <1375075929-6119-2-git-send-email-iamjoonsoo.kim@lge.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org List-ID: To: Hillf Danton Cc: Andrew Morton , Rik van Riel , Mel Gorman , Michal Hocko , "Aneesh Kumar K.V" , KAMEZAWA Hiroyuki , Hugh Dickins , Davidlohr Bueso , David Gibson , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Wanpeng Li , Naoya Horiguchi On Mon, Jul 29, 2013 at 03:24:46PM +0800, Hillf Danton wrote: > On Mon, Jul 29, 2013 at 1:31 PM, Joonsoo Kim wrote: > > alloc_huge_page_node() use dequeue_huge_page_node() without > > any validation check, so it can steal reserved page unconditionally. > > Well, why is it illegal to use reserved page here? Hello, Hillf. If we use reserved page here, other processes which are promised to use enough hugepages cannot get enough hugepages and can die. This is unexpected result to them. Thanks. > > > To fix it, check the number of free_huge_page in alloc_huge_page_node(). > > > > Signed-off-by: Joonsoo Kim > > > > diff --git a/mm/hugetlb.c b/mm/hugetlb.c > > index 6782b41..d971233 100644 > > --- a/mm/hugetlb.c > > +++ b/mm/hugetlb.c > > @@ -935,10 +935,11 @@ static struct page *alloc_buddy_huge_page(struct hstate *h, int nid) > > */ > > struct page *alloc_huge_page_node(struct hstate *h, int nid) > > { > > - struct page *page; > > + struct page *page = NULL; > > > > spin_lock(&hugetlb_lock); > > - page = dequeue_huge_page_node(h, nid); > > + if (h->free_huge_pages - h->resv_huge_pages > 0) > > + page = dequeue_huge_page_node(h, nid); > > spin_unlock(&hugetlb_lock); > > > > if (!page) > > -- > > 1.7.9.5 > > > > -- > To unsubscribe, send a message with 'unsubscribe linux-mm' in > the body to majordomo@kvack.org. For more info on Linux MM, > see: http://www.linux-mm.org/ . > Don't email: email@kvack.org -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org