bpf,docs: Remove references to bpf_cgroup_kptr_get()

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@manifault.com>
Link: https://lore.kernel.org/r/20230411041633.179404-3-void@manifault.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/Documentation/bpf/kfuncs.rst b/Documentation/bpf/kfuncs.rst
index d8a16c4bef7f09eb9f68ada6b10e91858994cb92..3b42cfe12437bad6be97177c4157eb242d23ebb6 100644 (file)
--- 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