The reclaim_clean_pages_from_list reclaims clean pages before
migration so cc.nr_migratepages should be updated.
Currently, there is no problem but it can be wrong if we
try to use the vaule in future.

Cc: Mel Gorman <mgor...@suse.de>
Cc: Michal Nazarewicz <min...@mina86.com>
Cc: Bartlomiej Zolnierkiewicz <b.zolnier...@samsung.com>
Cc: Marek Szyprowski <m.szyprow...@samsung.com>
Signed-off-by: Minchan Kim <minc...@kernel.org>
---
I found this problem during I develop new feature. :(

 mm/page_alloc.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 296bea9..4b7dced 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -5669,7 +5669,7 @@ static unsigned long pfn_max_align_up(unsigned long pfn)
 static int __alloc_contig_migrate_range(unsigned long start, unsigned long end)
 {
        /* This function is based on compact_zone() from compaction.c. */
-
+       unsigned long nr_reclaimed;
        unsigned long pfn = start;
        unsigned int tries = 0;
        int ret = 0;
@@ -5705,7 +5705,9 @@ static int __alloc_contig_migrate_range(unsigned long 
start, unsigned long end)
                        break;
                }
 
-               reclaim_clean_pages_from_list(cc.zone, &cc.migratepages);
+               nr_reclaimed = reclaim_clean_pages_from_list(cc.zone,
+                                                       &cc.migratepages);
+               cc.nr_migratepages -= nr_reclaimed;
 
                ret = migrate_pages(&cc.migratepages,
                                    alloc_migrate_target,
-- 
1.7.9.5

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