[PATCH v3] mm/damon/core: Fix return value from damos_wmark_metric_value

[PATCH v3] mm/damon/core: Fix return value from damos_wmark_metric_value

[Alex Rusuf]

damos_wmark_metric_value's return value is 'unsigned long', so
returning -EINVAL as 'unsigned long' may turn out to be
very different from the expected one (using 2's complement) and
treat as usual matric's value. So, fix that, checking if
returned value is not 0.

Fixes: ee801b7dd782 ("mm/damon/schemes: activate schemes based on a watermarks mechanism")
Signed-off-by: Alex Rusuf <yorha.op@gmail.com>
---
 mm/damon/core.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/mm/damon/core.c b/mm/damon/core.c
index 6d503c1c125e..172095e68c5d 100644
--- a/mm/damon/core.c
+++ b/mm/damon/core.c
@@ -1480,12 +1480,14 @@ static bool kdamond_need_stop(struct damon_ctx *ctx)
 	return true;
 }
 
-static unsigned long damos_wmark_metric_value(enum damos_wmark_metric metric)
+static int damos_get_wmark_metric_value(enum damos_wmark_metric metric,
+					unsigned long *metric_value)
 {
 	switch (metric) {
 	case DAMOS_WMARK_FREE_MEM_RATE:
-		return global_zone_page_state(NR_FREE_PAGES) * 1000 /
+		*metric_value = global_zone_page_state(NR_FREE_PAGES) * 1000 /
 		       totalram_pages();
+		return 0;
 	default:
 		break;
 	}
@@ -1500,10 +1502,9 @@ static unsigned long damos_wmark_wait_us(struct damos *scheme)
 {
 	unsigned long metric;
 
-	if (scheme->wmarks.metric == DAMOS_WMARK_NONE)
+	if (damos_get_wmark_metric_value(scheme->wmarks.metric, &metric))
 		return 0;
 
-	metric = damos_wmark_metric_value(scheme->wmarks.metric);
 	/* higher than high watermark or lower than low watermark */
 	if (metric > scheme->wmarks.high || scheme->wmarks.low > metric) {
 		if (scheme->wmarks.activated)
-- 
2.42.0

Re: [PATCH v3] mm/damon/core: Fix return value from damos_wmark_metric_value

[SeongJae Park]

Hi Alex,

On Sun, 28 Apr 2024 22:14:39 +0300 Alex Rusuf <yorha.op@gmail.com> wrote:

> damos_wmark_metric_value's return value is 'unsigned long', so
> returning -EINVAL as 'unsigned long' may turn out to be
> very different from the expected one (using 2's complement) and
> treat as usual matric's value. So, fix that, checking if
> returned value is not 0.
> 
> Fixes: ee801b7dd782 ("mm/damon/schemes: activate schemes based on a watermarks mechanism")
> Signed-off-by: Alex Rusuf <yorha.op@gmail.com>

Thank you for patiently revisioning the patch!

Reviewed-by: SeongJae Park <sj@kernel.org>


Thanks,
SJ

[...]