Subject: [PATCH bpf-next v3 2/3] bpf: libbpf: remove map name retry from bpf_create_map_xattr

From: Stanislav Fomichev <[email-masked]>
Date: Tue, 20 Nov 2018 17:11:20 -0800

Instead, check for a newly created caps.name bpf_object capability.
If kernel doesn't support names, don't specify the attribute.

See commit 23499442c319 ("bpf: libbpf: retry map creation without the
name") for rationale.

Signed-off-by: Stanislav Fomichev <[email-masked]>
---
 tools/lib/bpf/bpf.c    | 11 +----------
 tools/lib/bpf/libbpf.c |  3 ++-
 2 files changed, 3 insertions(+), 11 deletions(-)

diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
index 836447bb4f14..ce1822194590 100644
--- a/tools/lib/bpf/bpf.c
+++ b/tools/lib/bpf/bpf.c
@@ -69,7 +69,6 @@ int bpf_create_map_xattr(const struct bpf_create_map_attr *create_attr)
 {
 	__u32 name_len = create_attr->name ? strlen(create_attr->name) : 0;
 	union bpf_attr attr;
-	int ret;
 
 	memset(&attr, '\0', sizeof(attr));
 
@@ -87,15 +86,7 @@ int bpf_create_map_xattr(const struct bpf_create_map_attr *create_attr)
 	attr.map_ifindex = create_attr->map_ifindex;
 	attr.inner_map_fd = create_attr->inner_map_fd;
 
-	ret = sys_bpf(BPF_MAP_CREATE, &attr, sizeof(attr));
-	if (ret < 0 && errno == EINVAL && create_attr->name) {
-		/* Retry the same syscall, but without the name.
-		 * Pre v4.14 kernels don't support map names.
-		 */
-		memset(attr.map_name, 0, sizeof(attr.map_name));
-		return sys_bpf(BPF_MAP_CREATE, &attr, sizeof(attr));
-	}
-	return ret;
+	return sys_bpf(BPF_MAP_CREATE, &attr, sizeof(attr));
 }
 
 int bpf_create_map_node(enum bpf_map_type map_type, const char *name,
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 3f7f476d8751..bf45f285d0a0 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -1211,7 +1211,8 @@ bpf_object__create_maps(struct bpf_object *obj)
 			continue;
 		}
 
-		create_attr.name = map->name;
+		if (obj->caps.name)
+			create_attr.name = map->name;
 		create_attr.map_ifindex = map->map_ifindex;
 		create_attr.map_type = def->type;
 		create_attr.map_flags = def->map_flags;
-- 
2.19.1.1215.g8438c0b245-goog