The patch titled
Subject: mm,memory_hotplug: drop unneeded locking
has been added to the -mm tree. Its filename is
mmmemory_hotplug-drop-unneeded-locking.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/mmmemory_hotplug-drop-unneeded-locking.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/mmmemory_hotplug-drop-unneeded-locking.patch
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------------------------------------------------------
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.
Link: https://lkml.kernel.org/r/20210531093958.15021-1-osalvador@xxxxxxx
Signed-off-by: Oscar Salvador <osalvador@xxxxxxx>
Acked-by: David Hildenbrand <david@xxxxxxxxxx>
Cc: Anshuman Khandual <anshuman.khandual@xxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Pavel Tatashin <pasha.tatashin@xxxxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/memory_hotplug.c | 11 -----------
1 file changed, 11 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)
@@ -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);
}
@@ -638,15 +634,10 @@ void __ref move_pfn_range_to_zone(struct
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().
@@ -739,9 +730,7 @@ void adjust_present_page_count(struct zo
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,
_
Patches currently in -mm which might be from osalvador@xxxxxxx are
mmmemory_hotplug-drop-unneeded-locking.patch
