[PATCH] mm/vmscan: Fix NR_ISOLATED_FILE corruption on 64-bit

[Nicholas Piggin <npiggin@gmail.com>]

Previously the negated unsigned long would be cast back to signed long
which would have the correct negative value. After commit 730ec8c01a2b
("mm/vmscan.c: change prototype for shrink_page_list"), the large
unsigned int converts to a large positive signed long.

Symptoms include CMA allocations hanging forever holding the cma_mutex
due to alloc_contig_range->...->isolate_migratepages_block waiting
forever in "while (unlikely(too_many_isolated(pgdat)))".

Cc: linux-mm@kvack.org
Cc: Maninder Singh <maninder1.s@samsung.com>
Cc: Vaneet Narang <v.narang@samsung.com>
Cc: Maninder Singh <maninder1.s@samsung.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Amit Sahrawat <a.sahrawat@samsung.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Fixes: 730ec8c01a2b ("mm/vmscan.c: change prototype for shrink_page_list")
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
 mm/vmscan.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 1b8f0e059767..92c507bacf09 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1516,7 +1516,7 @@ unsigned int reclaim_clean_pages_from_list(struct zone *zone,
 	nr_reclaimed = shrink_page_list(&clean_pages, zone->zone_pgdat, &sc,
 			TTU_IGNORE_ACCESS, &stat, true);
 	list_splice(&clean_pages, page_list);
-	mod_node_page_state(zone->zone_pgdat, NR_ISOLATED_FILE, -nr_reclaimed);
+	mod_node_page_state(zone->zone_pgdat, NR_ISOLATED_FILE, -(long)nr_reclaimed);
 	/*
 	 * Since lazyfree pages are isolated from file LRU from the beginning,
 	 * they will rotate back to anonymous LRU in the end if it failed to
-- 
2.23.0