[RFC PATCH] mm/damon: handle zero sampling interval in damon_max_nr_accesses()

[RFC PATCH] mm/damon: handle zero sampling interval in damon_max_nr_accesses()

[SeongJae Park]

damon_max_nr_accesses() causes divide-by-zero if sampling interval is
zero.  Fix it by handling the case.

The issue was dicovered [1] by Sashiko.

[1] https://lore.kernel.org/20260619202459.145010-1-sj@kernel.org

Fixes: 198f0f4c58b9 ("mm/damon/vaddr,paddr: support pageout prioritization")
Cc: <stable@vger.kernel.org> # 5.16.x
Signed-off-by: SeongJae Park <sj@kernel.org>
---
 include/linux/damon.h | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/include/linux/damon.h b/include/linux/damon.h
index 64d75c78f4df4..b6fbe6089abc6 100644
--- a/include/linux/damon.h
+++ b/include/linux/damon.h
@@ -1066,8 +1066,10 @@ static inline bool damon_target_has_pid(const struct damon_ctx *ctx)
 
 static inline unsigned int damon_max_nr_accesses(const struct damon_attrs *attrs)
 {
+	unsigned long sample_interval = attrs->sample_interval ? : 1;
+
 	/* {aggr,sample}_interval are unsigned long, hence could overflow */
-	return min(attrs->aggr_interval / attrs->sample_interval,
+	return min(attrs->aggr_interval / sample_interval,
 			(unsigned long)UINT_MAX);
 }
 

base-commit: 7a58ae62cdf3c006a53b805bbb12079ab2621a07
-- 
2.47.3