linux-kernel - Re: [PATCH] mm,memory_hotplug: Drop unneeded locking

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Date:   Tue, 1 Jun 2021 09:47:42 +0200
From:   Oscar Salvador <osalvador@...e.de>
To:     Anshuman Khandual <anshuman.khandual@....com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        David Hildenbrand <david@...hat.com>,
        Michal Hocko <mhocko@...nel.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Pavel Tatashin <pasha.tatashin@...een.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm,memory_hotplug: Drop unneeded locking

On Tue, Jun 01, 2021 at 10:47:31AM +0530, Anshuman Khandual wrote:
> Should also just drop zone_span_write[lock|unlock]() helpers as there
> are no users left ?

Yes, definitely.
Andrew, can you squash this on top? Thanks:

diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
index a7fd2c3ccb77..27d8ba1d32cb 100644
--- a/include/linux/memory_hotplug.h
+++ b/include/linux/memory_hotplug.h
@@ -67,10 +67,6 @@ struct range mhp_get_pluggable_range(bool need_mapping);
 
 /*
  * Zone resizing functions
- *
- * Note: any attempt to resize a zone should has pgdat_resize_lock()
- * zone_span_writelock() both held. This ensure the size of a zone
- * can't be changed while pgdat_resize_lock() held.
  */
 static inline unsigned zone_span_seqbegin(struct zone *zone)
 {
@@ -80,14 +76,6 @@ static inline int zone_span_seqretry(struct zone *zone, unsigned iv)
 {
 	return read_seqretry(&zone->span_seqlock, iv);
 }
-static inline void zone_span_writelock(struct zone *zone)
-{
-	write_seqlock(&zone->span_seqlock);
-}
-static inline void zone_span_writeunlock(struct zone *zone)
-{
-	write_sequnlock(&zone->span_seqlock);
-}
 static inline void zone_seqlock_init(struct zone *zone)
 {
 	seqlock_init(&zone->span_seqlock);
@@ -233,8 +221,6 @@ static inline int zone_span_seqretry(struct zone *zone, unsigned iv)
 {
 	return 0;
 }
-static inline void zone_span_writelock(struct zone *zone) {}
-static inline void zone_span_writeunlock(struct zone *zone) {}
 static inline void zone_seqlock_init(struct zone *zone) {}
 
 static inline int try_online_node(int nid)


-- 
Oscar Salvador
SUSE L3