[bpf-next,v5,1/2] bpf: Add bpf_task_under_cgroup() kfunc

Commit Message

Feng Zhou May 4, 2023, 3:15 a.m. UTC

From: Feng Zhou <[e-mail]>

Add a kfunc that's similar to the bpf_current_task_under_cgroup.
The difference is that it is a designated task.

When hook sched related functions, sometimes it is necessary to
specify a task instead of the current task.

Signed-off-by: Feng Zhou <[e-mail]>
---
 kernel/bpf/helpers.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

Comments

Yonghong Song May 4, 2023, 2:29 p.m. UTC | #1

On 5/3/23 8:15 PM, Feng zhou wrote:
> From: Feng Zhou <[e-mail]>
> 
> Add a kfunc that's similar to the bpf_current_task_under_cgroup.
> The difference is that it is a designated task.
> 
> When hook sched related functions, sometimes it is necessary to
> specify a task instead of the current task.
> 
> Signed-off-by: Feng Zhou <[e-mail]>

You can carry my Ack from previous revision since there
is no change to the patch.

Acked-by: Yonghong Song <[e-mail]>

Feng Zhou May 5, 2023, 3:20 a.m. UTC | #2

在 2023/5/4 22:29, Yonghong Song 写道:
> 
> 
> On 5/3/23 8:15 PM, Feng zhou wrote:
>> From: Feng Zhou <[e-mail]>
>>
>> Add a kfunc that's similar to the bpf_current_task_under_cgroup.
>> The difference is that it is a designated task.
>>
>> When hook sched related functions, sometimes it is necessary to
>> specify a task instead of the current task.
>>
>> Signed-off-by: Feng Zhou <[e-mail]>
> 
> You can carry my Ack from previous revision since there
> is no change to the patch.
> 
> Acked-by: Yonghong Song <[e-mail]>

Will do

Patch

diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index bb6b4637ebf2..453cbd312366 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -2149,6 +2149,25 @@  __bpf_kfunc struct cgroup *bpf_cgroup_from_id(u64 cgid)
 		return NULL;
 	return cgrp;
 }
+
+/**
+ * bpf_task_under_cgroup - wrap task_under_cgroup_hierarchy() as a kfunc, test
+ * task's membership of cgroup ancestry.
+ * @task: the task to be tested
+ * @ancestor: possible ancestor of @task's cgroup
+ *
+ * Tests whether @task's default cgroup hierarchy is a descendant of @ancestor.
+ * It follows all the same rules as cgroup_is_descendant, and only applies
+ * to the default hierarchy.
+ */
+__bpf_kfunc long bpf_task_under_cgroup(struct task_struct *task,
+				       struct cgroup *ancestor)
+{
+	if (unlikely(!ancestor || !task))
+		return -EINVAL;
+
+	return task_under_cgroup_hierarchy(task, ancestor);
+}
 #endif /* CONFIG_CGROUPS */
 
 /**
@@ -2400,6 +2419,7 @@  BTF_ID_FLAGS(func, bpf_cgroup_acquire, KF_ACQUIRE | KF_RCU | KF_RET_NULL)
 BTF_ID_FLAGS(func, bpf_cgroup_release, KF_RELEASE)
 BTF_ID_FLAGS(func, bpf_cgroup_ancestor, KF_ACQUIRE | KF_RCU | KF_RET_NULL)
 BTF_ID_FLAGS(func, bpf_cgroup_from_id, KF_ACQUIRE | KF_RET_NULL)
+BTF_ID_FLAGS(func, bpf_task_under_cgroup, KF_RCU)
 #endif
 BTF_ID_FLAGS(func, bpf_task_from_pid, KF_ACQUIRE | KF_RET_NULL)
 BTF_SET8_END(generic_btf_ids)