[PATCH 5.9 212/255] mm/vmscan: fix NR_ISOLATED_FILE corruption on 64-bit

[Greg Kroah-Hartman]

From: Nicholas Piggin <npiggin@xxxxxxxxx>

commit 2da9f6305f306ffbbb44790675799328fb73119d upstream.

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)))".

[akpm@xxxxxxxxxxxxxxxxxxxx: fix -stat.nr_lazyfree_fail as well, per Michal]

Fixes: 730ec8c01a2b ("mm/vmscan.c: change prototype for shrink_page_list")
Signed-off-by: Nicholas Piggin <npiggin@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Cc: Vaneet Narang <v.narang@xxxxxxxxxxx>
Cc: Maninder Singh <maninder1.s@xxxxxxxxxxx>
Cc: Amit Sahrawat <a.sahrawat@xxxxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Link: https://lkml.kernel.org/r/20201029032320.1448441-1-npiggin@xxxxxxxxx
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 mm/vmscan.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1514,7 +1514,8 @@ unsigned int reclaim_clean_pages_from_li
 	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
@@ -1524,7 +1525,7 @@ unsigned int reclaim_clean_pages_from_li
 	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;
 }