linux-kernel - Re: [Xen-devel] [PATCHv3 01/10] mm: memory hotplug with an existing resource

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Date:	Thu, 13 Aug 2015 13:40:03 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	David Vrabel <david.vrabel@...rix.com>
Cc:	<linux-kernel@...r.kernel.org>, <xen-devel@...ts.xenproject.org>,
	Daniel Kiper <daniel.kiper@...cle.com>, <linux-mm@...ck.org>,
	"Boris Ostrovsky" <boris.ostrovsky@...cle.com>,
	Tang Chen <tangchen@...fujitsu.com>,
	Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>
Subject: Re: [Xen-devel] [PATCHv3 01/10] mm: memory hotplug with an existing
 resource

On Thu, 13 Aug 2015 11:21:43 +0100 David Vrabel <david.vrabel@...rix.com> wrote:

> On 30/07/15 18:03, David Vrabel wrote:
> > Add add_memory_resource() to add memory using an existing "System RAM"
> > resource.  This is useful if the memory region is being located by
> > finding a free resource slot with allocate_resource().
> > 
> > Xen guests will make use of this in their balloon driver to hotplug
> > arbitrary amounts of memory in response to toolstack requests.
> 
> Ping?  This enables a useful feature for Xen guests.
> 

Looks OK to me.  I've cc'ed some memory_hotplug.c developers.  If
they're OK with it, please add the patch to the (Xen?) tree which uses
it.




Add add_memory_resource() to add memory using an existing "System RAM"
resource.  This is useful if the memory region is being located by
finding a free resource slot with allocate_resource().

Xen guests will make use of this in their balloon driver to hotplug
arbitrary amounts of memory in response to toolstack requests.

Signed-off-by: David Vrabel <david.vrabel@...rix.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
---
 include/linux/memory_hotplug.h |  2 ++
 mm/memory_hotplug.c            | 28 +++++++++++++++++++++-------
 2 files changed, 23 insertions(+), 7 deletions(-)

diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
index 6ffa0ac..c76d371 100644
--- a/include/linux/memory_hotplug.h
+++ b/include/linux/memory_hotplug.h
@@ -11,6 +11,7 @@ struct zone;
 struct pglist_data;
 struct mem_section;
 struct memory_block;
+struct resource;
 
 #ifdef CONFIG_MEMORY_HOTPLUG
 
@@ -266,6 +267,7 @@ static inline void remove_memory(int nid, u64 start, u64 size) {}
 extern int walk_memory_range(unsigned long start_pfn, unsigned long end_pfn,
 		void *arg, int (*func)(struct memory_block *, void *));
 extern int add_memory(int nid, u64 start, u64 size);
+extern int add_memory_resource(int nid, struct resource *resource);
 extern int zone_for_memory(int nid, u64 start, u64 size, int zone_default);
 extern int arch_add_memory(int nid, u64 start, u64 size);
 extern int offline_pages(unsigned long start_pfn, unsigned long nr_pages);
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 003dbe4..169770a 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1224,23 +1224,21 @@ int zone_for_memory(int nid, u64 start, u64 size, int zone_default)
 }
 
 /* we are OK calling __meminit stuff here - we have CONFIG_MEMORY_HOTPLUG */
-int __ref add_memory(int nid, u64 start, u64 size)
+int __ref add_memory_resource(int nid, struct resource *res)
 {
+	u64 start, size;
 	pg_data_t *pgdat = NULL;
 	bool new_pgdat;
 	bool new_node;
-	struct resource *res;
 	int ret;
 
+	start = res->start;
+	size = resource_size(res);
+
 	ret = check_hotplug_memory_range(start, size);
 	if (ret)
 		return ret;
 
-	res = register_memory_resource(start, size);
-	ret = -EEXIST;
-	if (!res)
-		return ret;
-
 	{	/* Stupid hack to suppress address-never-null warning */
 		void *p = NODE_DATA(nid);
 		new_pgdat = !p;
@@ -1290,6 +1288,22 @@ out:
 	mem_hotplug_done();
 	return ret;
 }
+EXPORT_SYMBOL_GPL(add_memory_resource);
+
+int __ref add_memory(int nid, u64 start, u64 size)
+{
+	struct resource *res;
+	int ret;
+
+	res = register_memory_resource(start, size);
+	if (!res)
+		return -EEXIST;
+
+	ret = add_memory_resource(nid, res);
+	if (ret < 0)
+		release_memory_resource(res);
+	return ret;
+}
 EXPORT_SYMBOL_GPL(add_memory);
 
 #ifdef CONFIG_MEMORY_HOTREMOVE
-- 
2.1.4

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