mm, compaction: fast_find_migrateblock() should return pfn in the target zone

At present, pages not in the target zone are added to cc->migratepages
list in isolate_migratepages_block().  As a result, pages may migrate
between nodes unintentionally.

This would be a serious problem for older kernels without commit
f5342e7522a7b22f ("mm: memcontrol: remove the pgdata parameter of
mem_cgroup_page_lruvec"), because it can corrupt the lru list by
handling pages in list without holding proper lru_lock.

Avoid returning a pfn outside the target zone in the case that it is
not aligned with a pageblock boundary.  Otherwise
isolate_migratepages_block() will handle pages not in the target zone.

Link: https://lkml.kernel.org/r/20220511044300.4069-1-yamamoto.rei@jp.fujitsu.com
Fixes: 0017a7d5b850 ("mm, compaction: use free lists to quickly locate a migration source")
Signed-off-by: Rei Yamamoto <yamamoto.rei@jp.fujitsu.com>
Reviewed-by: Miaohe Lin <linmiaohe@huawei.com>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Cc: Don Dutile <ddutile@redhat.com>
Cc: Wonhyuk Yang <vvghjk1234@gmail.com>
Cc: Rei Yamamoto <yamamoto.rei@jp.fujitsu.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/compaction.c b/mm/compaction.c
index 0e0ef9e44530f663ca5481fc38926c3b4373b8c2..1f89b969c12bf5d76f10b4adcf3b6dec707a1cfc 100644 (file)
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -1848,6 +1848,8 @@ static unsigned long fast_find_migrateblock(struct compact_control *cc)
 
                                update_fast_start_pfn(cc, free_pfn);
                                pfn = pageblock_start_pfn(free_pfn);
+                               if (pfn < cc->zone->zone_start_pfn)
+                                       pfn = cc->zone->zone_start_pfn;
                                cc->fast_search_fail = 0;
                                found_block = true;
                                set_pageblock_skip(freepage);