[PATCH net-next] mm, oom: keep oom_adj under or at upper limit when printing [v2]

[PATCH net-next] mm, oom: keep oom_adj under or at upper limit when printing [v2]

[Charles Haithcock]

For oom_score_adj values in the range [942,999], the current
calculations will print 16 for oom_adj. This patch simply limits the
output so output is inline with docs.

v2: moved the change to after put task to make sure the task is
    released asap
Signed-off-by: Charles Haithcock <chaithco@redhat.com>
---
 fs/proc/base.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/fs/proc/base.c b/fs/proc/base.c
index 617db4e0faa0..eafabeaf21d1 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -1049,6 +1049,8 @@ static ssize_t oom_adj_read(struct file *file, char __user *buf, size_t count,
 		oom_adj = (task->signal->oom_score_adj * -OOM_DISABLE) /
 			  OOM_SCORE_ADJ_MAX;
 	put_task_struct(task);
+	if (oom_adj > OOM_ADJUST_MAX)
+		oom_adj = OOM_ADJUST_MAX;
 	len = snprintf(buffer, sizeof(buffer), "%d\n", oom_adj);
 	return simple_read_from_buffer(buf, count, ppos, buffer, len);
 }
-- 
2.25.1

Re: [PATCH net-next] mm, oom: keep oom_adj under or at upper limit when printing [v2]

[Michal Hocko]

On Tue 20-10-20 10:51:30, Charles Haithcock wrote:
> For oom_score_adj values in the range [942,999], the current
> calculations will print 16 for oom_adj. This patch simply limits the
> output so output is inline with docs.
> 
> v2: moved the change to after put task to make sure the task is
>     released asap
> Signed-off-by: Charles Haithcock <chaithco@redhat.com>

OK, this seems to be broken since the scaling has been introduced.
oom_score is deprecated but it is true that the fix is trivial.
Now that you have added this clamping we can drop the oom_score_adj ==
OOM_SCORE_ADJ_MAX branch as well.

Have you found out this by code inspeciton or some userspace actually
cares?

Anyway
Acked-by: Michal Hocko <mhocko@suse.com>

> ---
>  fs/proc/base.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/fs/proc/base.c b/fs/proc/base.c
> index 617db4e0faa0..eafabeaf21d1 100644
> --- a/fs/proc/base.c
> +++ b/fs/proc/base.c
> @@ -1049,6 +1049,8 @@ static ssize_t oom_adj_read(struct file *file, char __user *buf, size_t count,
>  		oom_adj = (task->signal->oom_score_adj * -OOM_DISABLE) /
>  			  OOM_SCORE_ADJ_MAX;
>  	put_task_struct(task);
> +	if (oom_adj > OOM_ADJUST_MAX)
> +		oom_adj = OOM_ADJUST_MAX;
>  	len = snprintf(buffer, sizeof(buffer), "%d\n", oom_adj);
>  	return simple_read_from_buffer(buf, count, ppos, buffer, len);
>  }
> -- 
> 2.25.1
> 

-- 
Michal Hocko
SUSE Labs