[PATCH] mm, sparse: drop pgdat_resize_lock in sparse_add/remove_one_section()

[Wei Yang <richard.weiyang@gmail.com>]

pgdat_resize_lock is used to protect pgdat's memory region information
like: node_start_pfn, node_present_pages, etc.

In function sparse_add/remove_one_section(), those data is not touched.
This means it is not necessary to acquire pgdat_resize_lock to protect
this area.

Since the information needed in sparse_add_one_section() is node id to
allocate proper memory. This patch also changes the prototype of
sparse_add_one_section() to pass node id directly. This is intended to
reduce misleading that sparse_add_one_section() would touch pgdat.

Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
---
 include/linux/memory_hotplug.h |  2 +-
 mm/memory_hotplug.c            |  2 +-
 mm/sparse.c                    | 17 +++++------------
 3 files changed, 7 insertions(+), 14 deletions(-)

diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
index 45a5affcab8a..3787d4e913e6 100644
--- a/include/linux/memory_hotplug.h
+++ b/include/linux/memory_hotplug.h
@@ -333,7 +333,7 @@ extern void move_pfn_range_to_zone(struct zone *zone, unsigned long start_pfn,
 		unsigned long nr_pages, struct vmem_altmap *altmap);
 extern int offline_pages(unsigned long start_pfn, unsigned long nr_pages);
 extern bool is_memblock_offlined(struct memory_block *mem);
-extern int sparse_add_one_section(struct pglist_data *pgdat,
+extern int sparse_add_one_section(int nid,
 		unsigned long start_pfn, struct vmem_altmap *altmap);
 extern void sparse_remove_one_section(struct zone *zone, struct mem_section *ms,
 		unsigned long map_offset, struct vmem_altmap *altmap);
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index f626e7e5f57b..5b3a3d7b4466 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -253,7 +253,7 @@ static int __meminit __add_section(int nid, unsigned long phys_start_pfn,
 	if (pfn_valid(phys_start_pfn))
 		return -EEXIST;
 
-	ret = sparse_add_one_section(NODE_DATA(nid), phys_start_pfn, altmap);
+	ret = sparse_add_one_section(nid, phys_start_pfn, altmap);
 	if (ret < 0)
 		return ret;
 
diff --git a/mm/sparse.c b/mm/sparse.c
index 33307fc05c4d..a4fdbcb21514 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -662,25 +662,24 @@ static void free_map_bootmem(struct page *memmap)
  * set.  If this is <=0, then that means that the passed-in
  * map was not consumed and must be freed.
  */
-int __meminit sparse_add_one_section(struct pglist_data *pgdat,
-		unsigned long start_pfn, struct vmem_altmap *altmap)
+int __meminit sparse_add_one_section(int nid, unsigned long start_pfn,
+				     struct vmem_altmap *altmap)
 {
 	unsigned long section_nr = pfn_to_section_nr(start_pfn);
 	struct mem_section *ms;
 	struct page *memmap;
 	unsigned long *usemap;
-	unsigned long flags;
 	int ret;
 
 	/*
 	 * no locking for this, because it does its own
 	 * plus, it does a kmalloc
 	 */
-	ret = sparse_index_init(section_nr, pgdat->node_id);
+	ret = sparse_index_init(section_nr, nid);
 	if (ret < 0 && ret != -EEXIST)
 		return ret;
 	ret = 0;
-	memmap = kmalloc_section_memmap(section_nr, pgdat->node_id, altmap);
+	memmap = kmalloc_section_memmap(section_nr, nid, altmap);
 	if (!memmap)
 		return -ENOMEM;
 	usemap = __kmalloc_section_usemap();
@@ -689,8 +688,6 @@ int __meminit sparse_add_one_section(struct pglist_data *pgdat,
 		return -ENOMEM;
 	}
 
-	pgdat_resize_lock(pgdat, &flags);
-
 	ms = __pfn_to_section(start_pfn);
 	if (ms->section_mem_map & SECTION_MARKED_PRESENT) {
 		ret = -EEXIST;
@@ -707,7 +704,6 @@ int __meminit sparse_add_one_section(struct pglist_data *pgdat,
 	sparse_init_one_section(ms, section_nr, memmap, usemap);
 
 out:
-	pgdat_resize_unlock(pgdat, &flags);
 	if (ret < 0) {
 		kfree(usemap);
 		__kfree_section_memmap(memmap, altmap);
@@ -769,10 +765,8 @@ void sparse_remove_one_section(struct zone *zone, struct mem_section *ms,
 		unsigned long map_offset, struct vmem_altmap *altmap)
 {
 	struct page *memmap = NULL;
-	unsigned long *usemap = NULL, flags;
-	struct pglist_data *pgdat = zone->zone_pgdat;
+	unsigned long *usemap = NULL;
 
-	pgdat_resize_lock(pgdat, &flags);
 	if (ms->section_mem_map) {
 		usemap = ms->pageblock_flags;
 		memmap = sparse_decode_mem_map(ms->section_mem_map,
@@ -780,7 +774,6 @@ void sparse_remove_one_section(struct zone *zone, struct mem_section *ms,
 		ms->section_mem_map = 0;
 		ms->pageblock_flags = NULL;
 	}
-	pgdat_resize_unlock(pgdat, &flags);
 
 	clear_hwpoisoned_pages(memmap + map_offset,
 			PAGES_PER_SECTION - map_offset);
-- 
2.15.1