* [PATCH -next] mm: memcg: adjust the warning when seq_buf overflows
@ 2024-06-28 7:23 Xiu Jianfeng
2024-06-28 7:45 ` Michal Hocko
0 siblings, 1 reply; 5+ messages in thread
From: Xiu Jianfeng @ 2024-06-28 7:23 UTC (permalink / raw)
To: hannes, mhocko, roman.gushchin, shakeel.butt, muchun.song, akpm
Cc: cgroups, linux-mm, linux-kernel
Currently it uses WARN_ON_ONCE() if seq_buf overflows when user reads
memory.stat, the only advantage of WARN_ON_ONCE is that the splat is
so verbose that it gets noticed. And also it panics the system if
panic_on_warn is enabled. It seems like the warning is just an over
reaction and a simple pr_warn should just achieve the similar effect.
Suggested-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Xiu Jianfeng <xiujianfeng@huawei.com>
---
mm/memcontrol.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index c251bbe35f4b..8e5590ac43d7 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1484,7 +1484,8 @@ static void memory_stat_format(struct mem_cgroup *memcg, struct seq_buf *s)
memcg_stat_format(memcg, s);
else
memcg1_stat_format(memcg, s);
- WARN_ON_ONCE(seq_buf_has_overflowed(s));
+ if (seq_buf_has_overflowed(s))
+ pr_warn("%s: Warning, stat buffer overflow, please report\n", __func__);
}
/**
--
2.34.1
^ permalink raw reply related [flat|nested] 5+ messages in thread* Re: [PATCH -next] mm: memcg: adjust the warning when seq_buf overflows
2024-06-28 7:23 [PATCH -next] mm: memcg: adjust the warning when seq_buf overflows Xiu Jianfeng
@ 2024-06-28 7:45 ` Michal Hocko
2024-06-28 7:55 ` xiujianfeng
2024-06-28 8:09 ` xiujianfeng
0 siblings, 2 replies; 5+ messages in thread
From: Michal Hocko @ 2024-06-28 7:45 UTC (permalink / raw)
To: Xiu Jianfeng
Cc: hannes, roman.gushchin, shakeel.butt, muchun.song, akpm, cgroups,
linux-mm, linux-kernel
On Fri 28-06-24 07:23:33, Xiu Jianfeng wrote:
> Currently it uses WARN_ON_ONCE() if seq_buf overflows when user reads
> memory.stat, the only advantage of WARN_ON_ONCE is that the splat is
> so verbose that it gets noticed. And also it panics the system if
> panic_on_warn is enabled. It seems like the warning is just an over
> reaction and a simple pr_warn should just achieve the similar effect.
>
> Suggested-by: Michal Hocko <mhocko@suse.com>
> Signed-off-by: Xiu Jianfeng <xiujianfeng@huawei.com>
Acked-by: Michal Hocko <mhocko@suse.com>
I would just squash this with other patch removing it from
memcg_stat_format. But this is up to you.
Thanks!
> ---
> mm/memcontrol.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index c251bbe35f4b..8e5590ac43d7 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -1484,7 +1484,8 @@ static void memory_stat_format(struct mem_cgroup *memcg, struct seq_buf *s)
> memcg_stat_format(memcg, s);
> else
> memcg1_stat_format(memcg, s);
> - WARN_ON_ONCE(seq_buf_has_overflowed(s));
> + if (seq_buf_has_overflowed(s))
> + pr_warn("%s: Warning, stat buffer overflow, please report\n", __func__);
> }
>
> /**
> --
> 2.34.1
>
--
Michal Hocko
SUSE Labs
^ permalink raw reply [flat|nested] 5+ messages in thread* Re: [PATCH -next] mm: memcg: adjust the warning when seq_buf overflows
2024-06-28 7:45 ` Michal Hocko
@ 2024-06-28 7:55 ` xiujianfeng
2024-06-28 8:09 ` xiujianfeng
1 sibling, 0 replies; 5+ messages in thread
From: xiujianfeng @ 2024-06-28 7:55 UTC (permalink / raw)
To: Michal Hocko
Cc: hannes, roman.gushchin, shakeel.butt, muchun.song, akpm, cgroups,
linux-mm, linux-kernel
On 2024/6/28 15:45, Michal Hocko wrote:
> On Fri 28-06-24 07:23:33, Xiu Jianfeng wrote:
>> Currently it uses WARN_ON_ONCE() if seq_buf overflows when user reads
>> memory.stat, the only advantage of WARN_ON_ONCE is that the splat is
>> so verbose that it gets noticed. And also it panics the system if
>> panic_on_warn is enabled. It seems like the warning is just an over
>> reaction and a simple pr_warn should just achieve the similar effect.
>>
>> Suggested-by: Michal Hocko <mhocko@suse.com>
>> Signed-off-by: Xiu Jianfeng <xiujianfeng@huawei.com>
>
> Acked-by: Michal Hocko <mhocko@suse.com>
>
> I would just squash this with other patch removing it from
> memcg_stat_format. But this is up to you.
Thanks, the other patch has already been merged into the -next branch by
Andrew. In this situation, I'm not quite clear whether I should send a
small separate patch, or squash them and send a v2. If Andrew wants, I
can do it.
>
> Thanks!
>
>> ---
>> mm/memcontrol.c | 3 ++-
>> 1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
>> index c251bbe35f4b..8e5590ac43d7 100644
>> --- a/mm/memcontrol.c
>> +++ b/mm/memcontrol.c
>> @@ -1484,7 +1484,8 @@ static void memory_stat_format(struct mem_cgroup *memcg, struct seq_buf *s)
>> memcg_stat_format(memcg, s);
>> else
>> memcg1_stat_format(memcg, s);
>> - WARN_ON_ONCE(seq_buf_has_overflowed(s));
>> + if (seq_buf_has_overflowed(s))
>> + pr_warn("%s: Warning, stat buffer overflow, please report\n", __func__);
>> }
>>
>> /**
>> --
>> 2.34.1
>>
>
^ permalink raw reply [flat|nested] 5+ messages in thread* Re: [PATCH -next] mm: memcg: adjust the warning when seq_buf overflows
2024-06-28 7:45 ` Michal Hocko
2024-06-28 7:55 ` xiujianfeng
@ 2024-06-28 8:09 ` xiujianfeng
2024-06-28 8:15 ` Michal Hocko
1 sibling, 1 reply; 5+ messages in thread
From: xiujianfeng @ 2024-06-28 8:09 UTC (permalink / raw)
To: Michal Hocko
Cc: hannes, roman.gushchin, shakeel.butt, muchun.song, akpm, cgroups,
linux-mm, linux-kernel
On 2024/6/28 15:45, Michal Hocko wrote:
> On Fri 28-06-24 07:23:33, Xiu Jianfeng wrote:
>> Currently it uses WARN_ON_ONCE() if seq_buf overflows when user reads
>> memory.stat, the only advantage of WARN_ON_ONCE is that the splat is
>> so verbose that it gets noticed. And also it panics the system if
>> panic_on_warn is enabled. It seems like the warning is just an over
>> reaction and a simple pr_warn should just achieve the similar effect.
>>
>> Suggested-by: Michal Hocko <mhocko@suse.com>
>> Signed-off-by: Xiu Jianfeng <xiujianfeng@huawei.com>
>
> Acked-by: Michal Hocko <mhocko@suse.com>
>
> I would just squash this with other patch removing it from
> memcg_stat_format. But this is up to you.
Sorry, I might have misunderstood, if you can squash them, it looks good
to me, thanks.
>
> Thanks!
>
>> ---
>> mm/memcontrol.c | 3 ++-
>> 1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
>> index c251bbe35f4b..8e5590ac43d7 100644
>> --- a/mm/memcontrol.c
>> +++ b/mm/memcontrol.c
>> @@ -1484,7 +1484,8 @@ static void memory_stat_format(struct mem_cgroup *memcg, struct seq_buf *s)
>> memcg_stat_format(memcg, s);
>> else
>> memcg1_stat_format(memcg, s);
>> - WARN_ON_ONCE(seq_buf_has_overflowed(s));
>> + if (seq_buf_has_overflowed(s))
>> + pr_warn("%s: Warning, stat buffer overflow, please report\n", __func__);
>> }
>>
>> /**
>> --
>> 2.34.1
>>
>
^ permalink raw reply [flat|nested] 5+ messages in thread* Re: [PATCH -next] mm: memcg: adjust the warning when seq_buf overflows
2024-06-28 8:09 ` xiujianfeng
@ 2024-06-28 8:15 ` Michal Hocko
0 siblings, 0 replies; 5+ messages in thread
From: Michal Hocko @ 2024-06-28 8:15 UTC (permalink / raw)
To: xiujianfeng
Cc: hannes, roman.gushchin, shakeel.butt, muchun.song, akpm, cgroups,
linux-mm, linux-kernel
On Fri 28-06-24 16:09:02, xiujianfeng wrote:
>
>
> On 2024/6/28 15:45, Michal Hocko wrote:
> > On Fri 28-06-24 07:23:33, Xiu Jianfeng wrote:
> >> Currently it uses WARN_ON_ONCE() if seq_buf overflows when user reads
> >> memory.stat, the only advantage of WARN_ON_ONCE is that the splat is
> >> so verbose that it gets noticed. And also it panics the system if
> >> panic_on_warn is enabled. It seems like the warning is just an over
> >> reaction and a simple pr_warn should just achieve the similar effect.
> >>
> >> Suggested-by: Michal Hocko <mhocko@suse.com>
> >> Signed-off-by: Xiu Jianfeng <xiujianfeng@huawei.com>
> >
> > Acked-by: Michal Hocko <mhocko@suse.com>
> >
> > I would just squash this with other patch removing it from
> > memcg_stat_format. But this is up to you.
>
> Sorry, I might have misunderstood, if you can squash them, it looks good
> to me, thanks.
Andrew usually can do that even when the patch is in his tree. But as
I've said having 2 patches is ok as well.
--
Michal Hocko
SUSE Labs
^ permalink raw reply [flat|nested] 5+ messages in thread
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2024-06-28 7:23 [PATCH -next] mm: memcg: adjust the warning when seq_buf overflows Xiu Jianfeng
2024-06-28 7:45 ` Michal Hocko
2024-06-28 7:55 ` xiujianfeng
2024-06-28 8:09 ` xiujianfeng
2024-06-28 8:15 ` Michal Hocko
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