netdev - [PATCHv2 bpf 2/3] libbpf: check if pin

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Date:   Sat,  3 Oct 2020 16:55:04 +0800
From:   Hangbin Liu <liuhangbin@...il.com>
To:     bpf@...r.kernel.org
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        Andrii Nakryiko <andriin@...com>,
        Andrii Nakryiko <andrii.nakryiko@...il.com>,
        netdev@...r.kernel.org,
        Toke Høiland-Jørgensen <toke@...hat.com>,
        Hangbin Liu <liuhangbin@...il.com>
Subject: [PATCHv2 bpf 2/3] libbpf: check if pin_path was set even map fd exist

Say a user reuse map fd after creating a map manually and set the
pin_path, then load the object via libbpf.

In libbpf bpf_object__create_maps(), bpf_object__reuse_map() will
return 0 if there is no pinned map in map->pin_path. Then after
checking if map fd exist, we should also check if pin_path was set
and do bpf_map__pin() instead of continue the loop.

Fix it by creating map if fd not exist and continue checking pin_path
after that.

v2: keep if condition with existing order

Suggested-by: Andrii Nakryiko <andrii.nakryiko@...il.com>
Signed-off-by: Hangbin Liu <liuhangbin@...il.com>
---
 tools/lib/bpf/libbpf.c | 37 ++++++++++++++++++-------------------
 1 file changed, 18 insertions(+), 19 deletions(-)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index c8b5fe45682d..1fb3fd733b23 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -4245,29 +4245,28 @@ bpf_object__create_maps(struct bpf_object *obj)
 		if (map->fd >= 0) {
 			pr_debug("map '%s': skipping creation (preset fd=%d)\n",
 				 map->name, map->fd);
-			continue;
-		}
-
-		err = bpf_object__create_map(obj, map);
-		if (err)
-			goto err_out;
+		} else {
+			err = bpf_object__create_map(obj, map);
+			if (err)
+				goto err_out;
 
-		pr_debug("map '%s': created successfully, fd=%d\n", map->name,
-			 map->fd);
+			pr_debug("map '%s': created successfully, fd=%d\n",
+				 map->name, map->fd);
 
-		if (bpf_map__is_internal(map)) {
-			err = bpf_object__populate_internal_map(obj, map);
-			if (err < 0) {
-				zclose(map->fd);
-				goto err_out;
+			if (bpf_map__is_internal(map)) {
+				err = bpf_object__populate_internal_map(obj, map);
+				if (err < 0) {
+					zclose(map->fd);
+					goto err_out;
+				}
 			}
-		}
 
-		if (map->init_slots_sz) {
-			err = init_map_slots(map);
-			if (err < 0) {
-				zclose(map->fd);
-				goto err_out;
+			if (map->init_slots_sz) {
+				err = init_map_slots(map);
+				if (err < 0) {
+					zclose(map->fd);
+					goto err_out;
+				}
 			}
 		}
 
-- 
2.25.4