+ mm-page_alloc-disassociate-the-pcp-high-from-pcp-batch-fix-2.patch added to -mm tree

+ mm-page_alloc-disassociate-the-pcp-high-from-pcp-batch-fix-2.patch added to -mm tree

[akpm]

The patch titled
     Subject: mm/page_alloc: disassociate the pcp->high from pcp->batch -fix
has been added to the -mm tree.  Its filename is
     mm-page_alloc-disassociate-the-pcp-high-from-pcp-batch-fix-2.patch

This patch should soon appear at
    https://ozlabs.org/~akpm/mmots/broken-out/mm-page_alloc-disassociate-the-pcp-high-from-pcp-batch-fix-2.patch
and later at
    https://ozlabs.org/~akpm/mmotm/broken-out/mm-page_alloc-disassociate-the-pcp-high-from-pcp-batch-fix-2.patch

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------------------------------------------------------
From: Mel Gorman <mgorman@techsingularity.net>
Subject: mm/page_alloc: disassociate the pcp->high from pcp->batch -fix

Vlastimil Babka noted that __setup_per_zone_wmarks updating pcp->high did
not protect watermark-related sysctl handlers from a parallel memory
hotplug operations.  This patch moves the PCP update to
setup_per_zone_wmarks and updates the PCP high value while protected by
the pcp_batch_high_lock mutex.  As a side-effect, the zone_pcp_update
calls during memory hotplug operations becomes redundant and can be
removed.

This is a fix to the mmotm patch
mm-page_alloc-disassociate-the-pcp-high-from-pcp-batch.patch.  It'll cause
a conflict with
mm-page_alloc-adjust-pcp-high-after-cpu-hotplug-events.patch but the
resolution is simple as the zone_pcp_update callers in
setup_per_zone_wmarks no longer exist.

Link: https://lkml.kernel.org/r/20210528105925.GN30378@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/memory_hotplug.c |    6 +++---
 mm/page_alloc.c     |   14 ++++++++------
 2 files changed, 11 insertions(+), 9 deletions(-)

--- a/mm/memory_hotplug.c~mm-page_alloc-disassociate-the-pcp-high-from-pcp-batch-fix-2
+++ a/mm/memory_hotplug.c
@@ -961,7 +961,6 @@ int __ref online_pages(unsigned long pfn
 	node_states_set_node(nid, &arg);
 	if (need_zonelists_rebuild)
 		build_all_zonelists(NULL);
-	zone_pcp_update(zone);
 
 	/* Basic onlining is complete, allow allocation of onlined pages. */
 	undo_isolate_page_range(pfn, pfn + nr_pages, MIGRATE_MOVABLE);
@@ -974,6 +973,7 @@ int __ref online_pages(unsigned long pfn
 	 */
 	shuffle_zone(zone);
 
+	/* reinitialise watermarks and update pcp limits */
 	init_per_zone_wmark_min();
 
 	kswapd_run(nid);
@@ -1829,13 +1829,13 @@ int __ref offline_pages(unsigned long st
 	adjust_managed_page_count(pfn_to_page(start_pfn), -nr_pages);
 	adjust_present_page_count(zone, -nr_pages);
 
+	/* reinitialise watermarks and update pcp limits */
 	init_per_zone_wmark_min();
 
 	if (!populated_zone(zone)) {
 		zone_pcp_reset(zone);
 		build_all_zonelists(NULL);
-	} else
-		zone_pcp_update(zone);
+	}
 
 	node_states_clear_node(node, &arg);
 	if (arg.status_change_nid >= 0) {
--- a/mm/page_alloc.c~mm-page_alloc-disassociate-the-pcp-high-from-pcp-batch-fix-2
+++ a/mm/page_alloc.c
@@ -8198,12 +8198,6 @@ static void __setup_per_zone_wmarks(void
 		zone->_watermark[WMARK_LOW]  = min_wmark_pages(zone) + tmp;
 		zone->_watermark[WMARK_HIGH] = min_wmark_pages(zone) + tmp * 2;
 
-		/*
-		 * The watermark size have changed so update the pcpu batch
-		 * and high limits or the limits may be inappropriate.
-		 */
-		zone_set_pageset_high_and_batch(zone);
-
 		spin_unlock_irqrestore(&zone->lock, flags);
 	}
 
@@ -8220,11 +8214,19 @@ static void __setup_per_zone_wmarks(void
  */
 void setup_per_zone_wmarks(void)
 {
+	struct zone *zone;
 	static DEFINE_SPINLOCK(lock);
 
 	spin_lock(&lock);
 	__setup_per_zone_wmarks();
 	spin_unlock(&lock);
+
+	/*
+	 * The watermark size have changed so update the pcpu batch
+	 * and high limits or the limits may be inappropriate.
+	 */
+	for_each_zone(zone)
+		zone_pcp_update(zone);
 }
 
 /*
_

Patches currently in -mm which might be from mgorman@techsingularity.net are

mm-page_alloc-split-per-cpu-page-lists-and-zone-stats.patch
mm-page_alloc-split-per-cpu-page-lists-and-zone-stats-fix.patch
mm-page_alloc-split-per-cpu-page-lists-and-zone-stats-fix-fix.patch
mm-page_alloc-convert-per-cpu-list-protection-to-local_lock.patch
mm-page_alloc-convert-per-cpu-list-protection-to-local_lock-fix.patch
mm-vmstat-convert-numa-statistics-to-basic-numa-counters.patch
mm-vmstat-inline-numa-event-counter-updates.patch
mm-page_alloc-batch-the-accounting-updates-in-the-bulk-allocator.patch
mm-page_alloc-reduce-duration-that-irqs-are-disabled-for-vm-counters.patch
mm-page_alloc-explicitly-acquire-the-zone-lock-in-__free_pages_ok.patch
mm-page_alloc-avoid-conflating-irqs-disabled-with-zone-lock.patch
mm-page_alloc-update-pgfree-outside-the-zone-lock-in-__free_pages_ok.patch
mm-page_alloc-delete-vmpercpu_pagelist_fraction.patch
mm-page_alloc-disassociate-the-pcp-high-from-pcp-batch.patch
mm-page_alloc-disassociate-the-pcp-high-from-pcp-batch-fix-2.patch
mm-page_alloc-adjust-pcp-high-after-cpu-hotplug-events.patch
mm-page_alloc-scale-the-number-of-pages-that-are-batch-freed.patch
mm-page_alloc-limit-the-number-of-pages-on-pcp-lists-when-reclaim-is-active.patch
mm-page_alloc-introduce-vmpercpu_pagelist_high_fraction.patch
mm-page_alloc-introduce-vmpercpu_pagelist_high_fraction-fix.patch
mm-vmscan-remove-kerneldoc-like-comment-from-isolate_lru_pages.patch
mm-vmalloc-include-header-for-prototype-of-set_iounmap_nonlazy.patch
mm-page_alloc-make-should_fail_alloc_page-a-static-function-should_fail_alloc_page-static.patch
mm-mapping_dirty_helpers-remove-double-note-in-kerneldoc.patch
mm-early_ioremap-add-prototype-for-early_memremap_pgprot_adjust.patch
mm-memcontrolc-fix-kerneldoc-comment-for-mem_cgroup_calculate_protection.patch
mm-memory_hotplug-fix-kerneldoc-comment-for-__try_online_node.patch
mm-memory_hotplug-fix-kerneldoc-comment-for-__remove_memory.patch
mm-zbud-add-kerneldoc-fields-for-zbud_pool.patch
mm-z3fold-add-kerneldoc-fields-for-z3fold_pool.patch
mm-swap-make-swap_address_space-an-inline-function.patch
mm-mmap_lock-remove-dead-code-for-config_tracing-configurations.patch
mm-page_alloc-move-prototype-for-find_suitable_fallback.patch
mm-swap-make-node_data-an-inline-function-on-config_flatmem.patch