[PATCH v2 4/4] mm, memory_hotplug: reorganize new pgdat initialization

Michal Hocko
2021-12-14T10:08:02Z

From: Michal Hocko <mhocko@suse.com>

When a !node_online node is brought up it needs a hotplug specific
initialization because the node could be either uninitialized yet or it
could have been recycled after previous hotremove. hotadd_init_pgdat is
responsible for that.

Internal pgdat state is initialized at two places currently
- hotadd_init_pgdat
- free_area_init_core_hotplug
There is no real clear cut what should go where but this patch's chosen to
move the whole internal state initialization into free_area_init_core_hotplug.
hotadd_init_pgdat is still responsible to pull all the parts together -
most notably to initialize zonelists because those depend on the overall topology.

This patch doesn't introduce any functional change.

Signed-off-by: Michal Hocko <mhocko@suse.com>
---
include/linux/memory_hotplug.h | 2 +-
mm/memory_hotplug.c | 28 +++-------------------------
mm/page_alloc.c | 25 +++++++++++++++++++++++--
3 files changed, 27 insertions(+), 28 deletions(-)

diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
index 60f09d3ebb3d..76bf2de86def 100644
--- a/include/linux/memory_hotplug.h
+++ b/include/linux/memory_hotplug.h
@@ -319,7 +319,7 @@ extern void set_zone_contiguous(struct zone *zone);
extern void clear_zone_contiguous(struct zone *zone);

#ifdef CONFIG_MEMORY_HOTPLUG
-extern void __ref free_area_init_core_hotplug(int nid);
+extern void __ref free_area_init_core_hotplug(struct pglist_data *pgdat);
extern int __add_memory(int nid, u64 start, u64 size, mhp_t mhp_flags);
extern int add_memory(int nid, u64 start, u64 size, mhp_t mhp_flags);
extern int add_memory_resource(int nid, struct resource *resource,
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 2daa88ce8c80..ddae307152b8 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1165,39 +1165,16 @@ static pg_data_t __ref *hotadd_init_pgdat(int nid)
{
struct pglist_data *pgdat;

- pgdat = NODE_DATA(nid);
-
/*
* NODE_DATA is preallocated (free_area_init) but its internal
* state is not allocated completely. Add missing pieces.
* Completely offline nodes stay around and they just need
* reintialization.
*/
- if (pgdat->per_cpu_nodestats == &boot_nodestats) {
- pgdat->per_cpu_nodestats =
- alloc_percpu(struct per_cpu_nodestat);
- } else {
- int cpu;
- /*
- * Reset the nr_zones, order and highest_zoneidx before reuse.
- * Note that kswapd will init kswapd_highest_zoneidx properly
- * when it starts in the near future.
- */
- pgdat->nr_zones = 0;
- pgdat->kswapd_order = 0;
- pgdat->kswapd_highest_zoneidx = 0;
- for_each_online_cpu(cpu) {
- struct per_cpu_nodestat *p;
-
- p = per_cpu_ptr(pgdat->per_cpu_nodestats, cpu);
- memset(p, 0, sizeof(*p));
- }
- }
-
- pgdat->node_start_pfn = 0;
+ pgdat = NODE_DATA(nid);

/* init node's zones as empty zones, we don't have any present pages.*/
- free_area_init_core_hotplug(nid);
+ free_area_init_core_hotplug(pgdat);

/*
* The node we allocated has no zone fallback lists. For avoiding
@@ -1209,6 +1186,7 @@ static pg_data_t __ref *hotadd_init_pgdat(int nid)
* When memory is hot-added, all the memory is in offline state. So
* clear all zones' present_pages because they will be updated in
* online_pages() and offline_pages().
+ * TODO: should be in free_area_init_core_hotplug?
*/
reset_node_managed_pages(pgdat);
reset_node_present_pages(pgdat);
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index f2ceffadf4eb..34743dcd2d66 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -7442,12 +7442,33 @@ static void __meminit zone_init_internals(struct zone *zone, enum zone_type idx,
* NOTE: this function is only called during memory hotplug
*/
#ifdef CONFIG_MEMORY_HOTPLUG
-void __ref free_area_init_core_hotplug(int nid)
+void __ref free_area_init_core_hotplug(struct pglist_data *pgdat)
{
+ int nid = pgdat->node_id;
enum zone_type z;
- pg_data_t *pgdat = NODE_DATA(nid);
+ int cpu;

pgdat_init_internals(pgdat);
+
+ if (pgdat->per_cpu_nodestats == &boot_nodestats)
+ pgdat->per_cpu_nodestats = alloc_percpu(struct per_cpu_nodestat);
+
+ /*
+ * Reset the nr_zones, order and highest_zoneidx before reuse.
+ * Note that kswapd will init kswapd_highest_zoneidx properly
+ * when it starts in the near future.
+ */
+ pgdat->nr_zones = 0;
+ pgdat->kswapd_order = 0;
+ pgdat->kswapd_highest_zoneidx = 0;
+ pgdat->node_start_pfn = 0;
+ for_each_online_cpu(cpu) {
+ struct per_cpu_nodestat *p;
+
+ p = per_cpu_ptr(pgdat->per_cpu_nodestats, cpu);
+ memset(p, 0, sizeof(*p));
+ }
+
for (z = 0; z < MAX_NR_ZONES; z++)
zone_init_internals(&pgdat->node_zones[z], z, nid, 0);
}
--
2.30.2