[PATCH v2 4/4] mm/damon: fix divide by zero in damon_get_intervals_score()

[Honggyu Kim <honggyu.kim@sk.com>]

The current implementation allows having zero size regions with no
special reasons, but damon_get_intervals_score() gets crashed by divide
by zero when the region size is zero.

  [   29.403950] Oops: divide error: 0000 [#1] SMP NOPTI

This patch fixes the bug, but does not disallow zero size regions to
keep the backward compatibility since disallowing zero size regions
might be a breaking change for some users.

Fixes: f04b0fedbe71 ("mm/damon/core: implement intervals auto-tuning")
Signed-off-by: Honggyu Kim <honggyu.kim@sk.com>
Cc: Yunjeong Mun <yunjeong.mun@sk.com>
---
 mm/damon/core.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/mm/damon/core.c b/mm/damon/core.c
index b217e0120e09..e274a4d958d6 100644
--- a/mm/damon/core.c
+++ b/mm/damon/core.c
@@ -1448,7 +1448,10 @@ static unsigned long damon_get_intervals_score(struct damon_ctx *c)
 			access_events += sz_region * r->nr_accesses;
 		}
 	}
-	target_access_events = max_access_events * goal_bp / 10000;
+	if (likely(max_access_events) > 0)
+		target_access_events = max_access_events * goal_bp / 10000;
+	else
+		target_access_events = 1;
 	return access_events * 10000 / target_access_events;
 }
 
-- 
2.34.1