bpf: Document BPF_F_LOCK in syscall commands

Document the meaning of the BPF_F_LOCK flag for the map lookup/update
descriptions. Based on commit 96049f3afd50 ("bpf: introduce BPF_F_LOCK
flag").

Signed-off-by: Joe Stringer <joe@cilium.io>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Reviewed-by: Quentin Monnet <quentin@isovalent.com>
Acked-by: Toke Høiland-Jørgensen <toke@redhat.com>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20210302171947.2268128-4-joe@cilium.io

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 052bbfe65f774ba39a492b1fbe881ffa1594e852..eb9f059f0569fe45d49695c2de0bae778947af0d 100644 (file)
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -123,6 +123,14 @@ union bpf_iter_link_info {
  *             Look up an element with a given *key* in the map referred to
  *             by the file descriptor *map_fd*.
  *
+ *             The *flags* argument may be specified as one of the
+ *             following:
+ *
+ *             **BPF_F_LOCK**
+ *                     Look up the value of a spin-locked map without
+ *                     returning the lock. This must be specified if the
+ *                     elements contain a spinlock.
+ *
  *     Return
  *             Returns zero on success. On error, -1 is returned and *errno*
  *             is set appropriately.
@@ -140,6 +148,8 @@ union bpf_iter_link_info {
  *                     Create a new element only if it did not exist.
  *             **BPF_EXIST**
  *                     Update an existing element.
+ *             **BPF_F_LOCK**
+ *                     Update a spin_lock-ed map element.
  *
  *     Return
  *             Returns zero on success. On error, -1 is returned and *errno*