Merge branch 'Align BPF TCP CCs implementing cong_control() with non-BPF CCs'

Jörn-Thorben Hinz says:

====================

This series corrects some inconveniences for a BPF TCP CC that
implements and uses tcp_congestion_ops.cong_control(). Until now, such a
CC did not have all necessary write access to struct sock and
unnecessarily needed to implement cong_avoid().

v4:
 - Remove braces around single statements after if
 - Don’t check pointer passed to bpf_link__destroy()
v3:
 - Add a selftest writing sk_pacing_*
 - Add a selftest with incomplete tcp_congestion_ops
 - Add a selftest with unsupported get_info()
 - Remove an unused variable
 - Reword a comment about reg() in bpf_struct_ops_map_update_elem()
v2:
 - Drop redundant check for required functions and just rely on
   tcp_register_congestion_control() (Martin KaFai Lau)
====================

Reviewed-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 3 insertions, 4 deletions

diff --git a/kernel/bpf/bpf_struct_ops.c b/kernel/bpf/bpf_struct_ops.c
index d9a3c9207240..7e0068c3399c 100644
--- a/kernel/bpf/bpf_struct_ops.c
+++ b/kernel/bpf/bpf_struct_ops.c
@@ -503,10 +503,9 @@ static int bpf_struct_ops_map_update_elem(struct bpf_map *map, void *key,
 		goto unlock;
 	}
 
-	/* Error during st_ops->reg().  It is very unlikely since
-	 * the above init_member() should have caught it earlier
-	 * before reg().  The only possibility is if there was a race
-	 * in registering the struct_ops (under the same name) to
+	/* Error during st_ops->reg(). Can happen if this struct_ops needs to be
+	 * verified as a whole, after all init_member() calls. Can also happen if
+	 * there was a race in registering the struct_ops (under the same name) to
 	 * a sub-system through different struct_ops's maps.
 	 */
 	set_memory_nx((long)st_map->image, 1);