mm/compaction: correct comment of fast_find_migrateblock in isolate_migratepages

After 90ed667c03fe5 ("Revert "Revert "mm/compaction: fix set skip in
fast_find_migrateblock"""), we remove skip set in fast_find_migrateblock.
Correct comment that fast_find_block is used to avoid isolation_suitable
check for pageblock returned from fast_find_migrateblock because
fast_find_migrateblock will mark found pageblock skipped.

Instead, comment that fast_find_block is used to avoid a redundant check
of fast found pageblock which is already checked skip flag inside
fast_find_migrateblock.

Link: https://lkml.kernel.org/r/20230804110454.2935878-5-shikemeng@huaweicloud.com
Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/compaction.c b/mm/compaction.c
index 78826c433ef6937d2cbb275adfa5567de931bec3..3b204fbaa470202b2f089e9c5babc31caee74fd3 100644 (file)
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -1987,9 +1987,9 @@ static isolate_migrate_t isolate_migratepages(struct compact_control *cc)
                block_start_pfn = cc->zone->zone_start_pfn;
 
        /*
-        * fast_find_migrateblock marks a pageblock skipped so to avoid
-        * the isolation_suitable check below, check whether the fast
-        * search was successful.
+        * fast_find_migrateblock() has already ensured the pageblock is not
+        * set with a skipped flag, so to avoid the isolation_suitable check
+        * below again, check whether the fast search was successful.
         */
        fast_find_block = low_pfn != cc->migrate_pfn && !cc->fast_search_fail;