linux-kernel - Re: [PATCH 4/9] mm, memory_hotplug: get rid of is_zone_device

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Date:   Mon, 10 Apr 2017 18:31:34 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Jerome Glisse <jglisse@...hat.com>
Cc:     linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
        Mel Gorman <mgorman@...e.de>, Vlastimil Babka <vbabka@...e.cz>,
        Andrea Arcangeli <aarcange@...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@...il.com>
Subject: Re: [PATCH 4/9] mm, memory_hotplug: get rid of is_zone_device_section

On Mon 10-04-17 12:20:02, Jerome Glisse wrote:
> On Mon, Apr 10, 2017 at 01:03:46PM +0200, Michal Hocko wrote:
[...]
> > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> > index 342332f29364..1570b3eea493 100644
> > --- a/mm/memory_hotplug.c
> > +++ b/mm/memory_hotplug.c
> > @@ -493,7 +493,7 @@ static int __meminit __add_zone(struct zone *zone, unsigned long phys_start_pfn)
> >  }
> >  
> >  static int __meminit __add_section(int nid, struct zone *zone,
> > -					unsigned long phys_start_pfn)
> > +					unsigned long phys_start_pfn, bool want_memblock)
> >  {
> >  	int ret;
> >  
> > @@ -510,7 +510,10 @@ static int __meminit __add_section(int nid, struct zone *zone,
> >  	if (ret < 0)
> >  		return ret;
> >  
> > -	return register_new_memory(nid, __pfn_to_section(phys_start_pfn));
> > +	if (want_memblock)
> > +		ret = register_new_memory(nid, __pfn_to_section(phys_start_pfn));
> > +
> > +	return ret;
> >  }
> 
> The above is wrong for ZONE_DEVICE sparse_add_one_section() will return a
> positive value (on success) thus ret > 0 and other function in the hotplug
> path will interpret positive value as an error.
> 
> I suggest something like:
> 	if (!want_memblock)
> 		return 0;
> 
> 	return register_new_memory(nid, __pfn_to_section(phys_start_pfn));
> }

You are right! I will fold the following. Thanks!
---
>From cc44b4a465b889910e74b3ccc2d12f4dd1c79065 Mon Sep 17 00:00:00 2001
From: Michal Hocko <mhocko@...e.com>
Date: Mon, 10 Apr 2017 18:29:11 +0200
Subject: [PATCH] fold me "mm, memory_hotplug: get rid of
 is_zone_device_section"

- return 0 want_memblock == 0 from __add_section as per Jerome Glisse
---
 mm/memory_hotplug.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 035165ceefef..9942d8937d0a 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -299,7 +299,8 @@ void __init register_page_bootmem_info_node(struct pglist_data *pgdat)
 }
 #endif /* CONFIG_HAVE_BOOTMEM_INFO_NODE */
 
-static int __meminit __add_section(int nid, unsigned long phys_start_pfn, bool want_memblock)
+static int __meminit __add_section(int nid, unsigned long phys_start_pfn,
+		bool want_memblock)
 {
 	int ret;
 	int i;
@@ -328,10 +329,10 @@ static int __meminit __add_section(int nid, unsigned long phys_start_pfn, bool w
 		SetPageReserved(page);
 	}
 
-	if (want_memblock)
-		ret = register_new_memory(nid, __pfn_to_section(phys_start_pfn));
+	if (!want_memblock)
+		return 0
 
-	return ret;
+	return register_new_memory(nid, __pfn_to_section(phys_start_pfn));
 }
 
 /*
-- 
2.11.0


-- 
Michal Hocko
SUSE Labs