From: Oscar Salvador <osalvador@xxxxxxx>
Subject: mm,memory_hotplug: drop unneeded locking
Currently, memory-hotplug code takes zone's span_writelock and pgdat's
resize_lock when resizing the node/zone's spanned pages via
{move_pfn_range_to_zone(),remove_pfn_range_from_zone()} and when resizing
node and zone's present pages via adjust_present_page_count().
These locks are also taken during the initialization of the system at boot
time, where it protects parallel struct page initialization, but they
should not really be needed in memory-hotplug where all operations are a)
synchronized on device level and b) serialized by the mem_hotplug_lock
lock.
[akpm@xxxxxxxxxxxxxxxxxxxx: remove now-unused locals]
Link: https://lkml.kernel.org/r/20210531093958.15021-1-osalvador@xxxxxxx
Signed-off-by: Oscar Salvador <osalvador@xxxxxxx>
Acked-by: David Hildenbrand <david@xxxxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Cc: Anshuman Khandual <anshuman.khandual@xxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Pavel Tatashin <pasha.tatashin@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/memory_hotplug.c | 16 +---------------
1 file changed, 1 insertion(+), 15 deletions(-)
--- a/mm/memory_hotplug.c~mmmemory_hotplug-drop-unneeded-locking
+++ a/mm/memory_hotplug.c
@@ -329,7 +329,6 @@ static void shrink_zone_span(struct zone
unsigned long pfn;
int nid = zone_to_nid(zone);
- zone_span_writelock(zone);
if (zone->zone_start_pfn == start_pfn) {
/*
* If the section is smallest section in the zone, it need
@@ -362,7 +361,6 @@ static void shrink_zone_span(struct zone
zone->spanned_pages = 0;
}
}
- zone_span_writeunlock(zone);
}
static void update_pgdat_span(struct pglist_data *pgdat)
@@ -399,7 +397,7 @@ void __ref remove_pfn_range_from_zone(st
{
const unsigned long end_pfn = start_pfn + nr_pages;
struct pglist_data *pgdat = zone->zone_pgdat;
- unsigned long pfn, cur_nr_pages, flags;
+ unsigned long pfn, cur_nr_pages;
/* Poison struct pages because they are now uninitialized again. */
for (pfn = start_pfn; pfn < end_pfn; pfn += cur_nr_pages) {
@@ -424,10 +422,8 @@ void __ref remove_pfn_range_from_zone(st
clear_zone_contiguous(zone);
- pgdat_resize_lock(zone->zone_pgdat, &flags);
shrink_zone_span(zone, start_pfn, start_pfn + nr_pages);
update_pgdat_span(pgdat);
- pgdat_resize_unlock(zone->zone_pgdat, &flags);
set_zone_contiguous(zone);
}
@@ -634,19 +630,13 @@ void __ref move_pfn_range_to_zone(struct
{
struct pglist_data *pgdat = zone->zone_pgdat;
int nid = pgdat->node_id;
- unsigned long flags;
clear_zone_contiguous(zone);
- /* TODO Huh pgdat is irqsave while zone is not. It used to be like that before */
- pgdat_resize_lock(pgdat, &flags);
- zone_span_writelock(zone);
if (zone_is_empty(zone))
init_currently_empty_zone(zone, start_pfn, nr_pages);
resize_zone_range(zone, start_pfn, nr_pages);
- zone_span_writeunlock(zone);
resize_pgdat_range(pgdat, start_pfn, nr_pages);
- pgdat_resize_unlock(pgdat, &flags);
/*
* Subsection population requires care in pfn_to_online_page().
@@ -736,12 +726,8 @@ struct zone *zone_for_pfn_range(int onli
*/
void adjust_present_page_count(struct zone *zone, long nr_pages)
{
- unsigned long flags;
-
zone->present_pages += nr_pages;
- pgdat_resize_lock(zone->zone_pgdat, &flags);
zone->zone_pgdat->node_present_pages += nr_pages;
- pgdat_resize_unlock(zone->zone_pgdat, &flags);
}
int mhp_init_memmap_on_memory(unsigned long pfn, unsigned long nr_pages,
_
