mm: page_alloc: avoid false page outside zone error info

JIRA: https://issues.redhat.com/browse/RHEL-27743

This patch is a backport of the following upstream commit:
commit 82d9b8c
Author: Miaohe Lin <[email protected]>
Date:   Tue Jul 4 19:18:23 2023 +0800

    mm: page_alloc: avoid false page outside zone error info

    If pfn is outside zone boundaries in the first round, ret will be set to
    1.  But if pfn is changed to inside the zone boundaries in zone span
    seqretry path, ret is still set to 1 leading to false page outside zone
    error info.

    This is from code inspection.  The race window should be really small thus
    hard to trigger in real world.

    [[email protected]: code simplification, per Matthew]
    Link: https://lkml.kernel.org/r/[email protected]
    Fixes: bdc8cb9 ("[PATCH] memory hotplug locking: zone span seqlock")
    Signed-off-by: Miaohe Lin <[email protected]>
    Cc: Matthew Wilcox <[email protected]>
    Signed-off-by: Andrew Morton <[email protected]>

Signed-off-by: Rafael Aquini <[email protected]>

Author: Rafael Aquini

mm/page_alloc.c

@@ -460,7 +460,7 @@ void set_pageblock_migratetype(struct page *page, int migratetype)
 #ifdef CONFIG_DEBUG_VM
 static int page_outside_zone_boundaries(struct zone *zone, struct page *page)
 {
-	int ret = 0;
+	int ret;
 	unsigned seq;
 	unsigned long pfn = page_to_pfn(page);
 	unsigned long sp, start_pfn;
@@ -469,8 +469,7 @@ static int page_outside_zone_boundaries(struct zone *zone, struct page *page)
 		seq = zone_span_seqbegin(zone);
 		start_pfn = zone->zone_start_pfn;
 		sp = zone->spanned_pages;
-		if (!zone_spans_pfn(zone, pfn))
-			ret = 1;
+		ret = !zone_spans_pfn(zone, pfn);
 	} while (zone_span_seqretry(zone, seq));
 
 	if (ret)