[PATCH bpf-next v3] libbpf: add "bool skipped" to struct bpf_map

[Shuyi Cheng <chengshuyi@xxxxxxxxxxxxxxxxx>]

Fix error: "failed to pin map: Bad file descriptor, path:
/sys/fs/bpf/_rodata_str1_1."

In the old kernel, the global data map will not be created, see [0]. So
we should skip the pinning of the global data map to avoid
bpf_object__pin_maps returning error. Therefore, when the map is not
created, we mark “map->skipped" as true and then check during relocation
and during pinning.

Signed-off-by: Shuyi Cheng <chengshuyi@xxxxxxxxxxxxxxxxx>
---
v2: 
https://lore.kernel.org/bpf/CAEf4Bzbxf4kEtCEWBSonomEp7ZiKBD50k-U941i=okKfgKb6FQ@xxxxxxxxxxxxxx/T/#mb884d33b1b5b8e5dfb5a362af0d3c025510b5a4c
v2->v3:
-- adjust the "bool skipped" position

v1: 
https://lore.kernel.org/bpf/CAEf4BzbtQGnGZTLbTdy1GHK54f5S7YNFQak7BuEfaqGEwqNNJA@xxxxxxxxxxxxxx/T/#m80ec7f8bc69dbcf4a5945e2aa6f16145901afc40
v1->v2:
-- add "bool skipped" to struct bpf_map.
-- replace "bpf_map__is_internal(map) && !kernel_supports(obj, 
FEAT_GLOBAL_DATA))" with map->skipped

 tools/lib/bpf/libbpf.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 18d95c6a89fe..d027e1d620fc 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -431,6 +431,7 @@ struct bpf_map {
 	char *pin_path;
 	bool pinned;
 	bool reused;
+	bool skipped;
 	__u64 map_extra;
 };

@@ -5087,8 +5088,10 @@ bpf_object__create_maps(struct bpf_object *obj)
 		 * kernels.
 		 */
 		if (bpf_map__is_internal(map) &&
-		    !kernel_supports(obj, FEAT_GLOBAL_DATA))
+		    !kernel_supports(obj, FEAT_GLOBAL_DATA)) {
+			map->skipped = true;
 			continue;
+		}

 		retried = false;
 retry:
@@ -5717,8 +5720,7 @@ bpf_object__relocate_data(struct bpf_object *obj, 
struct bpf_program *prog)
 			} else {
 				const struct bpf_map *map = &obj->maps[relo->map_idx];

-				if (bpf_map__is_internal(map) &&
-				    !kernel_supports(obj, FEAT_GLOBAL_DATA)) {
+				if (map->skipped) {
 					pr_warn("prog '%s': relo #%d: kernel doesn't support global data\n",
 						prog->name, i);
 					return -ENOTSUP;
@@ -7926,6 +7928,9 @@ int bpf_object__pin_maps(struct bpf_object *obj, 
const char *path)
 		char *pin_path = NULL;
 		char buf[PATH_MAX];

+		if (map->skipped)
+			continue;
+
 		if (path) {
 			int len;

--
2.19.1.6.gb485710b