| Message ID | 20220715061609.48463-1-songyuanzheng@huawei.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | mm/damon/reclaim: fix 'enabled' is incorrectly set because 'system_wq' is not initialized | expand |
Hello Yuanzheng, On Fri, 15 Jul 2022 06:16:09 +0000 Yuanzheng Song <songyuanzheng@huawei.com> 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@huawei.com> > --- > 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
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@huawei.com> 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@huawei.com> >> --- >> 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 > .
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);
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(). Fixes: 294928293813 ("mm/damon/reclaim: schedule 'damon_reclaim_timer' only after 'system_wq' is initialized") Signed-off-by: Yuanzheng Song <songyuanzheng@huawei.com> --- mm/damon/reclaim.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-)