[PATCH] mm: vmscan: Avoid signedness error for GCC 5.4

[WangYuli <wangyuli@uniontech.com>]

To the compiler, (MAX_NR_TIERS - 1) (i.e., (4U - 1)) is unsigned,
whereas tier is a signed integer.

GCC 5.4 does not permit the minimum operation on such
type-inconsistent operands.

Cast it to a signed integer to circumvent this compiler error.

Fix follow error with gcc 5.4:
  mm/vmscan.c: In function ‘read_ctrl_pos’:
  mm/vmscan.c:3166:728: error: call to ‘__compiletime_assert_887’ declared with attribute error: min(tier, 4U - 1) signedness error

Fixes: 37a260870f2c ("mm/mglru: rework type selection")
Signed-off-by: WangYuli <wangyuli@uniontech.com>
---
 mm/vmscan.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 3783e45bfc92..29dce1aed962 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -3163,7 +3163,7 @@ static void read_ctrl_pos(struct lruvec *lruvec, int type, int tier, int gain,
 	pos->gain = gain;
 	pos->refaulted = pos->total = 0;
 
-	for (i = tier % MAX_NR_TIERS; i <= min(tier, MAX_NR_TIERS - 1); i++) {
+	for (i = tier % MAX_NR_TIERS; i <= min(tier, (int)(MAX_NR_TIERS - 1)); i++) {
 		pos->refaulted += lrugen->avg_refaulted[type][i] +
 				  atomic_long_read(&lrugen->refaulted[hist][type][i]);
 		pos->total += lrugen->avg_total[type][i] +
-- 
2.49.0