[PATCH] mm, compaction: make fast_isolate_around() robust against pfns from a wrong zone

[Vlastimil Babka]

TBD

Signed-off-by: Vlastimil Babka <vbabka@xxxxxxx>
---
 mm/compaction.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/mm/compaction.c b/mm/compaction.c
index 190ccdaa6c19..b75645e4678d 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -1288,7 +1288,7 @@ static void
 fast_isolate_around(struct compact_control *cc, unsigned long pfn, unsigned long nr_isolated)
 {
 	unsigned long start_pfn, end_pfn;
-	struct page *page = pfn_to_page(pfn);
+	struct page *page;
 
 	/* Do not search around if there are enough pages already */
 	if (cc->nr_freepages >= cc->nr_migratepages)
@@ -1300,7 +1300,11 @@ fast_isolate_around(struct compact_control *cc, unsigned long pfn, unsigned long
 
 	/* Pageblock boundaries */
 	start_pfn = pageblock_start_pfn(pfn);
-	end_pfn = min(pageblock_end_pfn(pfn), zone_end_pfn(cc->zone)) - 1;
+	end_pfn = min(pageblock_end_pfn(pfn), zone_end_pfn(cc->zone));
+
+	page = pageblock_pfn_to_page(start_pfn, end_pfn, cc->zone);
+	if (!page)
+		return;
 
 	/* Scan before */
 	if (start_pfn != pfn) {
@@ -1486,7 +1490,7 @@ fast_isolate_freepages(struct compact_control *cc)
 	}
 
 	cc->total_free_scanned += nr_scanned;
-	if (!page)
+	if (!page || page_zone(page) != cc->zone)
 		return cc->free_pfn;
 
 	low_pfn = page_to_pfn(page);
-- 
2.30.0