Commit d35963bf authored by SeongJae Park's avatar SeongJae Park Committed by Andrew Morton
Browse files

mm/damon/core: avoid divide-by-zero during monitoring results update 

When monitoring attributes are changed, DAMON updates access rate of the
monitoring results accordingly.  For that, it divides some values by the
maximum nr_accesses.  However, due to the type of the related variables,
simple division-based calculation of the divisor can return zero.  As a
result, divide-by-zero is possible.  Fix it by using
damon_max_nr_accesses(), which handles the case.

Link: https://lkml.kernel.org/r/20231019194924.100347-3-sj@kernel.org


Fixes: 2f5bef5a ("mm/damon/core: update monitoring results for new monitoring attributes")
Signed-off-by: default avatarSeongJae Park <sj@kernel.org>
Reported-by: default avatarJakub Acs <acsjakub@amazon.de>
Cc: <stable@vger.kernel.org>	[6.3+]
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 35f5d941

mm/damon/core.c

+2 −8
Original line number Diff line number Diff line
@@ -500,20 +500,14 @@ static unsigned int damon_age_for_new_attrs(unsigned int age, 
static unsigned int damon_accesses_bp_to_nr_accesses(

		unsigned int accesses_bp, struct damon_attrs *attrs)

{

	unsigned int max_nr_accesses =

		attrs->aggr_interval / attrs->sample_interval;



	return accesses_bp * max_nr_accesses / 10000;

	return accesses_bp * damon_max_nr_accesses(attrs) / 10000;

}



/* convert nr_accesses to access ratio in bp (per 10,000) */

static unsigned int damon_nr_accesses_to_accesses_bp(

		unsigned int nr_accesses, struct damon_attrs *attrs)

{

	unsigned int max_nr_accesses =

		attrs->aggr_interval / attrs->sample_interval;



	return nr_accesses * 10000 / max_nr_accesses;

	return nr_accesses * 10000 / damon_max_nr_accesses(attrs);

}



static unsigned int damon_nr_accesses_for_new_attrs(unsigned int nr_accesses,