linux-kernel - [PATCH v2 2/4] mm/memory_hotplug: Call register_mem_sect_under

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Message-Id: <20180622111839.10071-3-osalvador@techadventures.net>
Date:   Fri, 22 Jun 2018 13:18:37 +0200
From:   osalvador@...hadventures.net
To:     akpm@...ux-foundation.org
Cc:     mhocko@...e.com, vbabka@...e.cz, pasha.tatashin@...cle.com,
        Jonathan.Cameron@...wei.com, arbab@...ux.vnet.ibm.com,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Oscar Salvador <osalvador@...e.de>
Subject: [PATCH v2 2/4] mm/memory_hotplug: Call register_mem_sect_under_node

From: Oscar Salvador <osalvador@...e.de>

When hotpluging memory, it is possible that two calls are being made
to register_mem_sect_under_node().
One comes from __add_section()->hotplug_memory_register()
and the other from add_memory_resource()->link_mem_sections() if
we had to register a new node.

In case we had to register a new node, hotplug_memory_register()
will only handle/allocate the memory_block's since
register_mem_sect_under_node() will return right away because the
node it is not online yet.

I think it is better if we leave hotplug_memory_register() to
handle/allocate only memory_block's and make link_mem_sections()
to call register_mem_sect_under_node().

So this patch removes the call to register_mem_sect_under_node()
from hotplug_memory_register(), and moves the call to link_mem_sections()
out of the condition, so it will always be called.
In this way we only have one place where the memory sections
are registered.

Signed-off-by: Oscar Salvador <osalvador@...e.de>
Reviewed-by: Pavel Tatashin <pasha.tatashin@...cle.com>
---
 drivers/base/memory.c |  2 --
 mm/memory_hotplug.c   | 32 +++++++++++---------------------
 2 files changed, 11 insertions(+), 23 deletions(-)

diff --git a/drivers/base/memory.c b/drivers/base/memory.c
index f5e560188a18..c8a1cb0b6136 100644
--- a/drivers/base/memory.c
+++ b/drivers/base/memory.c
@@ -736,8 +736,6 @@ int hotplug_memory_register(int nid, struct mem_section *section)
 		mem->section_count++;
 	}
 
-	if (mem->section_count == sections_per_block)
-		ret = register_mem_sect_under_node(mem, nid, false);
 out:
 	mutex_unlock(&mem_sysfs_mutex);
 	return ret;
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 504ba120bdfc..e2ed64b994e5 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1123,6 +1123,7 @@ int __ref add_memory_resource(int nid, struct resource *res, bool online)
 	u64 start, size;
 	bool new_node = false;
 	int ret;
+	unsigned long start_pfn, nr_pages;
 
 	start = res->start;
 	size = resource_size(res);
@@ -1151,34 +1152,23 @@ int __ref add_memory_resource(int nid, struct resource *res, bool online)
 	if (ret < 0)
 		goto error;
 
-	/* we online node here. we can't roll back from here. */
-	node_set_online(nid);
-
 	if (new_node) {
-		unsigned long start_pfn = start >> PAGE_SHIFT;
-		unsigned long nr_pages = size >> PAGE_SHIFT;
-
-		ret = __register_one_node(nid);
-		if (ret)
-			goto register_fail;
-
-		/*
-		 * link memory sections under this node. This is already
-		 * done when creatig memory section in register_new_memory
-		 * but that depends to have the node registered so offline
-		 * nodes have to go through register_node.
-		 * TODO clean up this mess.
-		 */
-		ret = link_mem_sections(nid, start_pfn, nr_pages, false);
-register_fail:
-		/*
-		 * If sysfs file of new node can't create, cpu on the node
+		/* If sysfs file of new node can't be created, cpu on the node
 		 * can't be hot-added. There is no rollback way now.
 		 * So, check by BUG_ON() to catch it reluctantly..
+		 * We online node here. We can't roll back from here.
 		 */
+		node_set_online(nid);
+		ret = __register_one_node(nid);
 		BUG_ON(ret);
 	}
 
+	/* link memory sections under this node.*/
+	start_pfn = start >> PAGE_SHIFT;
+	nr_pages = size >> PAGE_SHIFT;
+	ret = link_mem_sections(nid, start_pfn, nr_pages, false);
+	BUG_ON(ret);
+
 	/* create new memmap entry */
 	firmware_map_add_hotplug(start, start + size, "System RAM");
 
-- 
2.13.6