[PATCH 1/2] mm/compaction: check the range to pageblock_pfn_to_page() is within the zone first

[Wei Yang <richard.weiyang@gmail.com>]

Function pageblock_pfn_to_page() is introduced by commit 7d49d8868336
("mm, compaction: reduce zone checking frequency in the migration scanner"),
where there is no requirement on start_pfn/end_pfn except they are in
the same pageblock.

So at that time, pageblock_pfn_to_page() would be passed with pfn
without compared with zone boundary.

But after commit 7cf91a98e607 ("mm/compaction: speed up
pageblock_pfn_to_page() when zone is contiguous"), pageblock_pfn_to_page()
would think the range is valid and in the same zone if zone->contiguous,
even the range doesn't belong to this zone.

For example, in fast_isolate_freepages(), min_pfn is assigned to
pageblock_start_pfn() and passed to pageblock_pfn_to_page() without
checking with zone_start_pfn. And mostly, the end_pfn is not checked
with zone_end_pfn() before using.

To make this function robust, check the range is within the zone first.

Fixes: 7cf91a98e607 ("mm/compaction: speed up pageblock_pfn_to_page() when zone is contiguous")
Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
---
 mm/internal.h | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/mm/internal.h b/mm/internal.h
index 38607b2821d9..8e1a3819c9f1 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -724,6 +724,9 @@ extern struct page *__pageblock_pfn_to_page(unsigned long start_pfn,
 static inline struct page *pageblock_pfn_to_page(unsigned long start_pfn,
 				unsigned long end_pfn, struct zone *zone)
 {
+	if (start_pfn < zone->zone_start_pfn || end_pfn > zone_end_pfn(zone))
+		return NULL;
+
 	if (zone->contiguous)
 		return pfn_to_page(start_pfn);
 
-- 
2.34.1