[PATCH 2/2] mm: don't rely on system state to detect hot-plug operations

[Laurent Dufour <ldufour@linux.ibm.com>]

Backport version to the 5.4-stable tree of the commit:

f85086f95fa3 ("mm: don't rely on system state to detect hot-plug operations")

Cc: stable@vger.kernel.org # 5.4.y
Signed-off-by: Laurent Dufour <ldufour@linux.ibm.com>
---
 drivers/base/node.c  | 85 ++++++++++++++++++++++++++++----------------
 include/linux/node.h | 11 +++---
 mm/memory_hotplug.c  |  3 +-
 3 files changed, 64 insertions(+), 35 deletions(-)

diff --git a/drivers/base/node.c b/drivers/base/node.c
index 296546ffed6c..9c6e6a7b9354 100644
--- a/drivers/base/node.c
+++ b/drivers/base/node.c
@@ -758,14 +758,36 @@ static int __ref get_nid_for_pfn(unsigned long pfn)
 	return pfn_to_nid(pfn);
 }
 
+static int do_register_memory_block_under_node(int nid,
+					       struct memory_block *mem_blk)
+{
+	int ret;
+
+	/*
+	 * If this memory block spans multiple nodes, we only indicate
+	 * the last processed node.
+	 */
+	mem_blk->nid = nid;
+
+	ret = sysfs_create_link_nowarn(&node_devices[nid]->dev.kobj,
+				       &mem_blk->dev.kobj,
+				       kobject_name(&mem_blk->dev.kobj));
+	if (ret)
+		return ret;
+
+	return sysfs_create_link_nowarn(&mem_blk->dev.kobj,
+				&node_devices[nid]->dev.kobj,
+				kobject_name(&node_devices[nid]->dev.kobj));
+}
+
 /* register memory section under specified node if it spans that node */
-static int register_mem_sect_under_node(struct memory_block *mem_blk,
-					 void *arg)
+static int register_mem_block_under_node_early(struct memory_block *mem_blk,
+					       void *arg)
 {
 	unsigned long memory_block_pfns = memory_block_size_bytes() / PAGE_SIZE;
 	unsigned long start_pfn = section_nr_to_pfn(mem_blk->start_section_nr);
 	unsigned long end_pfn = start_pfn + memory_block_pfns - 1;
-	int ret, nid = *(int *)arg;
+	int nid = *(int *)arg;
 	unsigned long pfn;
 
 	for (pfn = start_pfn; pfn <= end_pfn; pfn++) {
@@ -782,38 +804,33 @@ static int register_mem_sect_under_node(struct memory_block *mem_blk,
 		}
 
 		/*
-		 * We need to check if page belongs to nid only for the boot
-		 * case, during hotplug we know that all pages in the memory
-		 * block belong to the same node.
-		 */
-		if (system_state == SYSTEM_BOOTING) {
-			page_nid = get_nid_for_pfn(pfn);
-			if (page_nid < 0)
-				continue;
-			if (page_nid != nid)
-				continue;
-		}
-
-		/*
-		 * If this memory block spans multiple nodes, we only indicate
-		 * the last processed node.
+		 * We need to check if page belongs to nid only at the boot
+		 * case because node's ranges can be interleaved.
 		 */
-		mem_blk->nid = nid;
-
-		ret = sysfs_create_link_nowarn(&node_devices[nid]->dev.kobj,
-					&mem_blk->dev.kobj,
-					kobject_name(&mem_blk->dev.kobj));
-		if (ret)
-			return ret;
+		page_nid = get_nid_for_pfn(pfn);
+		if (page_nid < 0)
+			continue;
+		if (page_nid != nid)
+			continue;
 
-		return sysfs_create_link_nowarn(&mem_blk->dev.kobj,
-				&node_devices[nid]->dev.kobj,
-				kobject_name(&node_devices[nid]->dev.kobj));
+		return do_register_memory_block_under_node(nid, mem_blk);
 	}
 	/* mem section does not span the specified node */
 	return 0;
 }
 
+/*
+ * During hotplug we know that all pages in the memory block belong to the same
+ * node.
+ */
+static int register_mem_block_under_node_hotplug(struct memory_block *mem_blk,
+						 void *arg)
+{
+	int nid = *(int *)arg;
+
+	return do_register_memory_block_under_node(nid, mem_blk);
+}
+
 /*
  * Unregister a memory block device under the node it spans. Memory blocks
  * with multiple nodes cannot be offlined and therefore also never be removed.
@@ -829,11 +846,19 @@ void unregister_memory_block_under_nodes(struct memory_block *mem_blk)
 			  kobject_name(&node_devices[mem_blk->nid]->dev.kobj));
 }
 
-int link_mem_sections(int nid, unsigned long start_pfn, unsigned long end_pfn)
+int link_mem_sections(int nid, unsigned long start_pfn, unsigned long end_pfn,
+		      enum meminit_context context)
 {
+	walk_memory_blocks_func_t func;
+
+	if (context == MEMINIT_HOTPLUG)
+		func = register_mem_block_under_node_hotplug;
+	else
+		func = register_mem_block_under_node_early;
+
 	return walk_memory_blocks(PFN_PHYS(start_pfn),
 				  PFN_PHYS(end_pfn - start_pfn), (void *)&nid,
-				  register_mem_sect_under_node);
+				  func);
 }
 
 #ifdef CONFIG_HUGETLBFS
diff --git a/include/linux/node.h b/include/linux/node.h
index 4866f32a02d8..014ba3ab2efd 100644
--- a/include/linux/node.h
+++ b/include/linux/node.h
@@ -99,11 +99,13 @@ extern struct node *node_devices[];
 typedef  void (*node_registration_func_t)(struct node *);
 
 #if defined(CONFIG_MEMORY_HOTPLUG_SPARSE) && defined(CONFIG_NUMA)
-extern int link_mem_sections(int nid, unsigned long start_pfn,
-			     unsigned long end_pfn);
+int link_mem_sections(int nid, unsigned long start_pfn,
+		      unsigned long end_pfn,
+		      enum meminit_context context);
 #else
 static inline int link_mem_sections(int nid, unsigned long start_pfn,
-				    unsigned long end_pfn)
+				    unsigned long end_pfn,
+				    enum meminit_context context)
 {
 	return 0;
 }
@@ -128,7 +130,8 @@ static inline int register_one_node(int nid)
 		if (error)
 			return error;
 		/* link memory sections under this node */
-		error = link_mem_sections(nid, start_pfn, end_pfn);
+		error = link_mem_sections(nid, start_pfn, end_pfn,
+					  MEMINIT_EARLY);
 	}
 
 	return error;
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 6a4b3a01e1b6..308beca3ffeb 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1082,7 +1082,8 @@ int __ref add_memory_resource(int nid, struct resource *res)
 	}
 
 	/* link memory sections under this node.*/
-	ret = link_mem_sections(nid, PFN_DOWN(start), PFN_UP(start + size - 1));
+	ret = link_mem_sections(nid, PFN_DOWN(start), PFN_UP(start + size - 1),
+				MEMINIT_HOTPLUG);
 	BUG_ON(ret);
 
 	/* create new memmap entry */
-- 
2.28.0