[PATCH RFC 3/3] mm/memory_hotplug: Remove memory block devices before arch_remove_memory()

[David Hildenbrand <david@redhat.com>]

Let's factor out removing of memory block devices, which is only
necessary for memory added via add_memory() and friends that created
memory block devices. Remove the devices before calling
arch_remove_memory().

TODO: We should try to get rid of the errors that could be reported by
unregister_memory_block_under_nodes(). Ignoring failures is not that
nice.

Signed-off-by: David Hildenbrand <david@redhat.com>
---
 drivers/base/memory.c  | 41 +++++++++++++++--------------------------
 drivers/base/node.c    |  7 +++----
 include/linux/memory.h |  2 +-
 include/linux/node.h   |  6 ++----
 mm/memory_hotplug.c    | 10 ++++------
 5 files changed, 25 insertions(+), 41 deletions(-)

diff --git a/drivers/base/memory.c b/drivers/base/memory.c
index 847b33061e2e..fd8940c37129 100644
--- a/drivers/base/memory.c
+++ b/drivers/base/memory.c
@@ -752,40 +752,29 @@ int hotplug_memory_register(unsigned long start, unsigned long size)
 }
 
 #ifdef CONFIG_MEMORY_HOTREMOVE
-static int remove_memory_section(struct mem_section *section)
+void hotplug_memory_unregister(unsigned long start, unsigned long size)
 {
+	unsigned long block_nr_pages = memory_block_size_bytes() >> PAGE_SHIFT;
+	unsigned long start_pfn = PFN_DOWN(start);
+	unsigned long end_pfn = start_pfn + (size >> PAGE_SHIFT);
 	struct memory_block *mem;
+	unsigned long pfn;
 
-	mutex_lock(&mem_sysfs_mutex);
-
-	/*
-	 * Some users of the memory hotplug do not want/need memblock to
-	 * track all sections. Skip over those.
-	 */
-	mem = find_memory_block(section);
-	if (!mem)
-		goto out_unlock;
-
-	unregister_mem_sect_under_nodes(mem, __section_nr(section));
+	BUG_ON(!IS_ALIGNED(start, memory_block_size_bytes()));
+	BUG_ON(!IS_ALIGNED(size, memory_block_size_bytes()));
 
-	mem->section_count--;
-	if (mem->section_count == 0)
+	mutex_lock(&mem_sysfs_mutex);
+	for (pfn = start_pfn; pfn != end_pfn; pfn += block_nr_pages) {
+		mem = find_memory_block(__pfn_to_section(pfn));
+		if (!mem)
+			continue;
+		mem->section_count = 0;
+		unregister_memory_block_under_nodes(mem);
 		unregister_memory(mem);
-	else
-		put_device(&mem->dev);
-
-out_unlock:
+	}
 	mutex_unlock(&mem_sysfs_mutex);
-	return 0;
 }
 
-int unregister_memory_section(struct mem_section *section)
-{
-	if (!present_section(section))
-		return -EINVAL;
-
-	return remove_memory_section(section);
-}
 #endif /* CONFIG_MEMORY_HOTREMOVE */
 
 /* return true if the memory block is offlined, otherwise, return false */
diff --git a/drivers/base/node.c b/drivers/base/node.c
index 8598fcbd2a17..f9997770ac15 100644
--- a/drivers/base/node.c
+++ b/drivers/base/node.c
@@ -802,8 +802,7 @@ int register_mem_sect_under_node(struct memory_block *mem_blk, void *arg)
 }
 
 /* unregister memory section under all nodes that it spans */
-int unregister_mem_sect_under_nodes(struct memory_block *mem_blk,
-				    unsigned long phys_index)
+int unregister_memory_block_under_nodes(struct memory_block *mem_blk)
 {
 	NODEMASK_ALLOC(nodemask_t, unlinked_nodes, GFP_KERNEL);
 	unsigned long pfn, sect_start_pfn, sect_end_pfn;
@@ -816,8 +815,8 @@ int unregister_mem_sect_under_nodes(struct memory_block *mem_blk,
 		return -ENOMEM;
 	nodes_clear(*unlinked_nodes);
 
-	sect_start_pfn = section_nr_to_pfn(phys_index);
-	sect_end_pfn = sect_start_pfn + PAGES_PER_SECTION - 1;
+	sect_start_pfn = section_nr_to_pfn(mem_blk->start_section_nr);
+	sect_end_pfn = section_nr_to_pfn(mem_blk->end_section_nr);
 	for (pfn = sect_start_pfn; pfn <= sect_end_pfn; pfn++) {
 		int nid;
 
diff --git a/include/linux/memory.h b/include/linux/memory.h
index e275dc775834..414e43ab0881 100644
--- a/include/linux/memory.h
+++ b/include/linux/memory.h
@@ -113,7 +113,7 @@ extern int register_memory_isolate_notifier(struct notifier_block *nb);
 extern void unregister_memory_isolate_notifier(struct notifier_block *nb);
 int hotplug_memory_register(unsigned long start, unsigned long size);
 #ifdef CONFIG_MEMORY_HOTREMOVE
-extern int unregister_memory_section(struct mem_section *);
+void hotplug_memory_unregister(unsigned long start, unsigned long size);
 #endif
 extern int memory_dev_init(void);
 extern int memory_notify(unsigned long val, void *v);
diff --git a/include/linux/node.h b/include/linux/node.h
index 1a557c589ecb..02a29e71b175 100644
--- a/include/linux/node.h
+++ b/include/linux/node.h
@@ -139,8 +139,7 @@ extern int register_cpu_under_node(unsigned int cpu, unsigned int nid);
 extern int unregister_cpu_under_node(unsigned int cpu, unsigned int nid);
 extern int register_mem_sect_under_node(struct memory_block *mem_blk,
 						void *arg);
-extern int unregister_mem_sect_under_nodes(struct memory_block *mem_blk,
-					   unsigned long phys_index);
+extern int unregister_memory_block_under_nodes(struct memory_block *mem_blk);
 
 extern int register_memory_node_under_compute_node(unsigned int mem_nid,
 						   unsigned int cpu_nid,
@@ -176,8 +175,7 @@ static inline int register_mem_sect_under_node(struct memory_block *mem_blk,
 {
 	return 0;
 }
-static inline int unregister_mem_sect_under_nodes(struct memory_block *mem_blk,
-						  unsigned long phys_index)
+static inline int unregister_memory_block_under_nodes(struct memory_block *mem_blk)
 {
 	return 0;
 }
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 13ee0a26e034..041b93c5eede 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -518,14 +518,9 @@ static int __remove_section(struct zone *zone, struct mem_section *ms,
 {
 	unsigned long start_pfn;
 	int scn_nr;
-	int ret = -EINVAL;
 
 	if (!valid_section(ms))
-		return ret;
-
-	ret = unregister_memory_section(ms);
-	if (ret)
-		return ret;
+		return -EINVAL;
 
 	scn_nr = __section_nr(ms);
 	start_pfn = section_nr_to_pfn((unsigned long)scn_nr);
@@ -1875,6 +1870,9 @@ void __ref __remove_memory(int nid, u64 start, u64 size)
 	memblock_free(start, size);
 	memblock_remove(start, size);
 
+	/* remove memory block devices before removing memory */
+	hotplug_memory_unregister(start, size);
+
 	arch_remove_memory(nid, start, size, NULL);
 
 	try_offline_node(nid);
-- 
2.17.2