Hello,
在 2023/8/15 04:51, Jonathan Corbet 写道:
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?
Yes, indeed. We should guarantee that the policy_name is terminated with
a NULL character to avoid some undefined behavior.
Thanks for your helpful review.
------
Chuyi Zhou
