mm/vmscan: fix NR_ISOLATED_FILE corruption on 64-bit

Previously the negated unsigned long would be cast back to signed long
which would have the correct negative value.  After commit 730ec8c
("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)))".

[[email protected]: fix -stat.nr_lazyfree_fail as well, per Michal]

Fixes: 730ec8c ("mm/vmscan.c: change prototype for shrink_page_list")
Signed-off-by: Nicholas Piggin <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Acked-by: Michal Hocko <[email protected]>
Cc: Vaneet Narang <[email protected]>
Cc: Maninder Singh <[email protected]>
Cc: Amit Sahrawat <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Cc: <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Linus Torvalds <[email protected]>

mm/vmscan.c

@@ -1516,7 +1516,8 @@ 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
@@ -1526,7 +1527,7 @@ unsigned int reclaim_clean_pages_from_list(struct zone *zone,
 	mod_node_page_state(zone->zone_pgdat, NR_ISOLATED_ANON,
 			    stat.nr_lazyfree_fail);
 	mod_node_page_state(zone->zone_pgdat, NR_ISOLATED_FILE,
-			    -stat.nr_lazyfree_fail);
+			    -(long)stat.nr_lazyfree_fail);
 	return nr_reclaimed;
 }