Commit 27cacaad authored by Oscar Salvador's avatar Oscar Salvador Committed by Linus Torvalds
Browse files

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@linux-foundation.org: remove now-unused locals]

Link: https://lkml.kernel.org/r/20210531093958.15021-1-osalvador@suse.de


Signed-off-by: default avatarOscar Salvador <osalvador@suse.de>
Acked-by: default avatarDavid Hildenbrand <david@redhat.com>
Acked-by: default avatarMichal Hocko <mhocko@suse.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Pavel Tatashin <pasha.tatashin@soleen.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 786dee86

mm/memory_hotplug.c

+1 −15
Original line number Diff line number Diff line
@@ -329,7 +329,6 @@ static void shrink_zone_span(struct zone *zone, unsigned long start_pfn, 
	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, unsigned long start_pfn, 
			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(struct zone *zone, 
{

	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(struct zone *zone, 


	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 zone *zone, unsigned long start_pfn, 
{

	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 online_type, int nid, unsigned start_pfn, 
 */

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,