Chuyi Zhou <zhouchuyi@xxxxxxxxxxxxx> writes:
> This patch adds a new metadata policy_name in oom_control and report it
> in dump_header(), so we can know what has been the selection policy. In
> BPF program, we can call kfunc set_oom_policy_name to set the current
> user-defined policy name. The in-kernel policy_name is "default".
>
> Signed-off-by: Chuyi Zhou <zhouchuyi@xxxxxxxxxxxxx>
> ---
> include/linux/oom.h | 7 +++++++
> mm/oom_kill.c | 42 +++++++++++++++++++++++++++++++++++++++---
> 2 files changed, 46 insertions(+), 3 deletions(-)
So I have a possibly dumb question here...
> diff --git a/include/linux/oom.h b/include/linux/oom.h
> index 7d0c9c48a0c5..69d0f2ec6ea6 100644
> --- a/include/linux/oom.h
> +++ b/include/linux/oom.h
> @@ -22,6 +22,10 @@ enum oom_constraint {
> CONSTRAINT_MEMCG,
> };
>
> +enum {
> + POLICY_NAME_LEN = 16,
> +};
We've defined our name length, fine...
> /*
> * Details of the page allocation that triggered the oom killer that are used to
> * determine what should be killed.
> @@ -52,6 +56,9 @@ struct oom_control {
>
> /* Used to print the constraint info. */
> enum oom_constraint constraint;
> +
> + /* Used to report the policy info. */
> + char policy_name[POLICY_NAME_LEN];
> };
...that is the length of the array, appended to the structure...
> extern struct mutex oom_lock;
> diff --git a/mm/oom_kill.c b/mm/oom_kill.c
> index 255c9ef1d808..3239dcdba4d7 100644
> --- a/mm/oom_kill.c
> +++ b/mm/oom_kill.c
> @@ -443,6 +443,35 @@ static int dump_task(struct task_struct *p, void *arg)
> return 0;
> }
>
> +__bpf_kfunc void set_oom_policy_name(struct oom_control *oc, const char *src, size_t sz)
> +{
> + memset(oc->policy_name, 0, sizeof(oc->policy_name));
> +
> + if (sz > POLICY_NAME_LEN)
> + sz = POLICY_NAME_LEN;
> +
> + memcpy(oc->policy_name, src, sz);
> +}
This truncates the name, possibly leaving it without a terminating NUL
character, right?
> +__diag_push();
> +__diag_ignore_all("-Wmissing-prototypes",
> + "kfuncs which will be used in BPF programs");
> +
> +__weak noinline void bpf_set_policy_name(struct oom_control *oc)
> +{
> +}
> +
> +__diag_pop();
> +
> +BTF_SET8_START(bpf_oom_policy_kfunc_ids)
> +BTF_ID_FLAGS(func, set_oom_policy_name)
> +BTF_SET8_END(bpf_oom_policy_kfunc_ids)
> +
> +static const struct btf_kfunc_id_set bpf_oom_policy_kfunc_set = {
> + .owner = THIS_MODULE,
> + .set = &bpf_oom_policy_kfunc_ids,
> +};
> +
> /**
> * dump_tasks - dump current memory state of all system tasks
> * @oc: pointer to struct oom_control
> @@ -484,8 +513,8 @@ static void dump_oom_summary(struct oom_control *oc, struct task_struct *victim)
>
> static void dump_header(struct oom_control *oc, struct task_struct *p)
> {
> - pr_warn("%s invoked oom-killer: gfp_mask=%#x(%pGg), order=%d, oom_score_adj=%hd\n",
> - current->comm, oc->gfp_mask, &oc->gfp_mask, oc->order,
> + pr_warn("%s invoked oom-killer: gfp_mask=%#x(%pGg), order=%d, policy_name=%s, oom_score_adj=%hd\n",
> + current->comm, oc->gfp_mask, &oc->gfp_mask, oc->order, oc->policy_name,
...and if the policy name is unterminated, this print will run off the
end of the structure.
Am I missing something here?
Thanks,
jon
