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mm/damon/ops-common: avoid divide-by-zero during region hotness calculation 

When calculating the hotness of each region for the under-quota regions
prioritization, DAMON 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/20231019194924.100347-4-sj@kernel.org
Fixes: 198f0f4c58 ("mm/damon/vaddr,paddr: support pageout prioritization")
Signed-off-by: SeongJae Park <sj@kernel.org>
Reported-by: Jakub Acs <acsjakub@amazon.de>
Cc: <stable@vger.kernel.org>	[5.16+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
SeongJae Park 2023-10-19 19:49:22 +00:00 committed by Andrew Morton
parent d35963bfb0
commit 3bafc47d3c
1 changed files with 2 additions and 3 deletions
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5
mm/damon/ops-common.c
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@ -73,7 +73,6 @@ void damon_pmdp_mkold(pmd_t *pmd, struct vm_area_struct *vma, unsigned long addr
int damon_hot_score(struct damon_ctx *c, struct damon_region *r,
struct damos *s)
{
unsigned int max_nr_accesses;
int freq_subscore;
unsigned int age_in_sec;
int age_in_log, age_subscore;
@ -81,8 +80,8 @@ int damon_hot_score(struct damon_ctx *c, struct damon_region *r,
unsigned int age_weight = s->quota.weight_age;
int hotness;
max_nr_accesses = c->attrs.aggr_interval / c->attrs.sample_interval;
freq_subscore = r->nr_accesses * DAMON_MAX_SUBSCORE / max_nr_accesses;
freq_subscore = r->nr_accesses * DAMON_MAX_SUBSCORE /
damon_max_nr_accesses(&c->attrs);
age_in_sec = (unsigned long)r->age * c->attrs.aggr_interval / 1000000;
for (age_in_log = 0; age_in_log < DAMON_MAX_AGE_IN_LOG && age_in_sec;