Hello SJ,
Thank you very much for your reply, through your reply let me understand
this principle, so please ignore this patch.
Thanks,
Yuanzheng
On 2022/7/16 1:07, SeongJae Park wrote:
Hello Yuanzheng,
On Fri, 15 Jul 2022 06:16:09 +0000 Yuanzheng Song <songyuanzheng@xxxxxxxxxx> wrote:
The 'enabled' will be incorrectly set because the 'system_wq'
might not initialized yet. This results in 'enabled=true',
but the 'damon_reclaim_timer' is inactive. So fix it by moving
the judgment logic of the 'damon_reclaim_initialized' to the
start position of the enable_store().
Thank you for this patch!
In the case, however, 'damon_reclaim_init()' will activate
'damon_reclaim_timer', which will check the 'enabled' and start DAMON later.
So 'enabled' will inconsistently set while DAMON_RECLAIM is not really enabled
for a moment, but those will eventually be consistent. This patch could reduce
the duration of the inconsistent state.
However, this would break boot-time DAMON_RECLAIM enabling, which adds
'damon_reclaim.enabled=true' to the kernel parameter, as this change will set
'enabled' as 'false' in the early 'damon_reclaim_enabled_store()', so that the
later 'damon_reclaim_initialized()' activated 'damon_reclaim_timer' shows
'enabled' as 'false' and therefore doesn't start DAMON.
If there is anything I'm missing, please let me know.
Thanks,
SJ
Fixes: 294928293813 ("mm/damon/reclaim: schedule 'damon_reclaim_timer' only after 'system_wq' is initialized")
Signed-off-by: Yuanzheng Song <songyuanzheng@xxxxxxxxxx>
---
mm/damon/reclaim.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)
diff --git a/mm/damon/reclaim.c b/mm/damon/reclaim.c
index e69b807fefe4..b13d5a02bf2e 100644
--- a/mm/damon/reclaim.c
+++ b/mm/damon/reclaim.c
@@ -374,13 +374,14 @@ static bool damon_reclaim_initialized;
static int damon_reclaim_enabled_store(const char *val,
const struct kernel_param *kp)
{
- int rc = param_set_bool(val, kp);
-
- if (rc < 0)
- return rc;
+ int rc;
/* system_wq might not initialized yet */
if (!damon_reclaim_initialized)
+ return -EINVAL;
+
+ rc = param_set_bool(val, kp);
+ if (rc < 0)
return rc;
schedule_delayed_work(&damon_reclaim_timer, 0);
--
2.25.1
.
