linux-kernel - Re: [PATCH 11/14] mm, memory_hotplug: do not associate hotadded memory to zones until online

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Date:   Mon, 26 Jun 2017 07:38:19 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Wei Yang <richard.weiyang@...il.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        Mel Gorman <mgorman@...e.de>, Vlastimil Babka <vbabka@...e.cz>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Jerome Glisse <jglisse@...hat.com>,
        Reza Arbab <arbab@...ux.vnet.ibm.com>,
        Yasuaki Ishimatsu <yasu.isimatu@...il.com>,
        qiuxishi@...wei.com, Kani Toshimitsu <toshi.kani@....com>,
        slaoub@...il.com, Joonsoo Kim <js1304@...il.com>,
        Andi Kleen <ak@...ux.intel.com>,
        David Rientjes <rientjes@...gle.com>,
        Daniel Kiper <daniel.kiper@...cle.com>,
        Igor Mammedov <imammedo@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        Martin Schwidefsky <schwidefsky@...ibm.com>
Subject: Re: [PATCH 11/14] mm, memory_hotplug: do not associate hotadded
 memory to zones until online

On Sun 25-06-17 08:14:13, Wei Yang wrote:
> On Mon, May 15, 2017 at 10:58:24AM +0200, Michal Hocko wrote:
> >From: Michal Hocko <mhocko@...e.com>
> >
> [...]
> >+void move_pfn_range_to_zone(struct zone *zone,
> >+		unsigned long start_pfn, unsigned long nr_pages)
> >+{
> >+	struct pglist_data *pgdat = zone->zone_pgdat;
> >+	int nid = pgdat->node_id;
> >+	unsigned long flags;
> >+	unsigned long i;
> 
> This is an unused variable:
> 
>   mm/memory_hotplug.c: In function ‘move_pfn_range_to_zone’:
>   mm/memory_hotplug.c:895:16: warning: unused variable ‘i’ [-Wunused-variable]
> 
> Do you suggest me to write a patch or you would fix it in your later rework?

Please send a fix for your
http://lkml.kernel.org/r/20170616092335.5177-2-richard.weiyang@gmail.com
Andrew will fold it into that patch.

> 
> >+
> >+	if (zone_is_empty(zone))
> >+		init_currently_empty_zone(zone, start_pfn, nr_pages);
> >+
> >+	clear_zone_contiguous(zone);
> >+
> >+	/* TODO Huh pgdat is irqsave while zone is not. It used to be like that before */
> >+	pgdat_resize_lock(pgdat, &flags);
> >+	zone_span_writelock(zone);
> >+	resize_zone_range(zone, start_pfn, nr_pages);
> >+	zone_span_writeunlock(zone);
> >+	resize_pgdat_range(pgdat, start_pfn, nr_pages);
> >+	pgdat_resize_unlock(pgdat, &flags);
> >+
> >+	/*
> >+	 * TODO now we have a visible range of pages which are not associated
> >+	 * with their zone properly. Not nice but set_pfnblock_flags_mask
> >+	 * expects the zone spans the pfn range. All the pages in the range
> >+	 * are reserved so nobody should be touching them so we should be safe
> >+	 */
> >+	memmap_init_zone(nr_pages, nid, zone_idx(zone), start_pfn, MEMMAP_HOTPLUG);
> >+	for (i = 0; i < nr_pages; i++) {
> >+		unsigned long pfn = start_pfn + i;
> >+		set_page_links(pfn_to_page(pfn), zone_idx(zone), nid, pfn);
> > 	}
> > 
> >2.11.0
> 
> -- 
> Wei Yang
> Help you, Help me



-- 
Michal Hocko
SUSE Labs