The bpf_cgroup_kptr_get() kfunc has been removed, and
bpf_cgroup_acquire() / bpf_cgroup_release() now have the same semantics
as bpf_task_acquire() / bpf_task_release(). This patch updates the BPF
documentation to reflect this.
Signed-off-by: David Vernet <void@xxxxxxxxxxxxx>
---
Documentation/bpf/kfuncs.rst | 68 ------------------------------------
1 file changed, 68 deletions(-)
diff --git a/Documentation/bpf/kfuncs.rst b/Documentation/bpf/kfuncs.rst
index d8a16c4bef7f..3b42cfe12437 100644
--- a/Documentation/bpf/kfuncs.rst
+++ b/Documentation/bpf/kfuncs.rst
@@ -572,74 +572,6 @@ bpf_task_release() respectively, so we won't provide examples for them.
----
-You may also acquire a reference to a ``struct cgroup`` kptr that's already
-stored in a map using bpf_cgroup_kptr_get():
-
-.. kernel-doc:: kernel/bpf/helpers.c
- :identifiers: bpf_cgroup_kptr_get
-
-Here's an example of how it can be used:
-
-.. code-block:: c
-
- /* struct containing the struct task_struct kptr which is actually stored in the map. */
- struct __cgroups_kfunc_map_value {
- struct cgroup __kptr * cgroup;
- };
-
- /* The map containing struct __cgroups_kfunc_map_value entries. */
- struct {
- __uint(type, BPF_MAP_TYPE_HASH);
- __type(key, int);
- __type(value, struct __cgroups_kfunc_map_value);
- __uint(max_entries, 1);
- } __cgroups_kfunc_map SEC(".maps");
-
- /* ... */
-
- /**
- * A simple example tracepoint program showing how a
- * struct cgroup kptr that is stored in a map can
- * be acquired using the bpf_cgroup_kptr_get() kfunc.
- */
- SEC("tp_btf/cgroup_mkdir")
- int BPF_PROG(cgroup_kptr_get_example, struct cgroup *cgrp, const char *path)
- {
- struct cgroup *kptr;
- struct __cgroups_kfunc_map_value *v;
- s32 id = cgrp->self.id;
-
- /* Assume a cgroup kptr was previously stored in the map. */
- v = bpf_map_lookup_elem(&__cgroups_kfunc_map, &id);
- if (!v)
- return -ENOENT;
-
- /* Acquire a reference to the cgroup kptr that's already stored in the map. */
- kptr = bpf_cgroup_kptr_get(&v->cgroup);
- if (!kptr)
- /* If no cgroup was present in the map, it's because
- * we're racing with another CPU that removed it with
- * bpf_kptr_xchg() between the bpf_map_lookup_elem()
- * above, and our call to bpf_cgroup_kptr_get().
- * bpf_cgroup_kptr_get() internally safely handles this
- * race, and will return NULL if the task is no longer
- * present in the map by the time we invoke the kfunc.
- */
- return -EBUSY;
-
- /* Free the reference we just took above. Note that the
- * original struct cgroup kptr is still in the map. It will
- * be freed either at a later time if another context deletes
- * it from the map, or automatically by the BPF subsystem if
- * it's still present when the map is destroyed.
- */
- bpf_cgroup_release(kptr);
-
- return 0;
- }
-
-----
-
Other kfuncs available for interacting with ``struct cgroup *`` objects are
bpf_cgroup_ancestor() and bpf_cgroup_from_id(), allowing callers to access
the ancestor of a cgroup and find a cgroup by its ID, respectively. Both
--
2.40.0
