netdev - [RFC PATCH bpf-next v1 02/11] bpf: Convert bpf_selem_link

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Message-ID: <20250729182550.185356-3-ameryhung@gmail.com>
Date: Tue, 29 Jul 2025 11:25:40 -0700
From: Amery Hung <ameryhung@...il.com>
To: bpf@...r.kernel.org
Cc: netdev@...r.kernel.org,
	alexei.starovoitov@...il.com,
	andrii@...nel.org,
	daniel@...earbox.net,
	memxor@...il.com,
	kpsingh@...nel.org,
	martin.lau@...nel.org,
	yonghong.song@...ux.dev,
	song@...nel.org,
	haoluo@...gle.com,
	ameryhung@...il.com,
	kernel-team@...a.com
Subject: [RFC PATCH bpf-next v1 02/11] bpf: Convert bpf_selem_link_map to failable

To prepare for changing bpf_local_storage_map_bucket::lock to rqspinlock,
convert bpf_selem_link_map to failable. It still always succeeds and
returns 0 until the change happen. No functional change.

__must_check is added to the function declaration locally to make sure
all the callers are accounted for during the conversion.

Signed-off-by: Amery Hung <ameryhung@...il.com>
---
 include/linux/bpf_local_storage.h | 4 ++--
 kernel/bpf/bpf_local_storage.c    | 6 ++++--
 net/core/bpf_sk_storage.c         | 4 +++-
 3 files changed, 9 insertions(+), 5 deletions(-)

diff --git a/include/linux/bpf_local_storage.h b/include/linux/bpf_local_storage.h
index ab7244d8108f..dc56fa459ac9 100644
--- a/include/linux/bpf_local_storage.h
+++ b/include/linux/bpf_local_storage.h
@@ -182,8 +182,8 @@ void bpf_selem_link_storage_nolock(struct bpf_local_storage *local_storage,
 
 void bpf_selem_unlink(struct bpf_local_storage_elem *selem, bool reuse_now);
 
-void bpf_selem_link_map(struct bpf_local_storage_map *smap,
-			struct bpf_local_storage_elem *selem);
+int bpf_selem_link_map(struct bpf_local_storage_map *smap,
+		       struct bpf_local_storage_elem *selem);
 
 struct bpf_local_storage_elem *
 bpf_selem_alloc(struct bpf_local_storage_map *smap, void *owner, void *value,
diff --git a/kernel/bpf/bpf_local_storage.c b/kernel/bpf/bpf_local_storage.c
index 7e39b88ef795..95e2dcf919ac 100644
--- a/kernel/bpf/bpf_local_storage.c
+++ b/kernel/bpf/bpf_local_storage.c
@@ -435,8 +435,8 @@ static void bpf_selem_unlink_map_nolock(struct bpf_local_storage_elem *selem)
 		hlist_del_init_rcu(&selem->map_node);
 }
 
-void bpf_selem_link_map(struct bpf_local_storage_map *smap,
-			struct bpf_local_storage_elem *selem)
+int bpf_selem_link_map(struct bpf_local_storage_map *smap,
+		       struct bpf_local_storage_elem *selem)
 {
 	struct bpf_local_storage_map_bucket *b = select_bucket(smap, selem);
 	unsigned long flags;
@@ -445,6 +445,8 @@ void bpf_selem_link_map(struct bpf_local_storage_map *smap,
 	RCU_INIT_POINTER(SDATA(selem)->smap, smap);
 	hlist_add_head_rcu(&selem->map_node, &b->list);
 	raw_spin_unlock_irqrestore(&b->lock, flags);
+
+	return 0;
 }
 
 static void bpf_selem_link_map_nolock(struct bpf_local_storage_map *smap,
diff --git a/net/core/bpf_sk_storage.c b/net/core/bpf_sk_storage.c
index 2e538399757f..fac5cf385785 100644
--- a/net/core/bpf_sk_storage.c
+++ b/net/core/bpf_sk_storage.c
@@ -194,7 +194,9 @@ int bpf_sk_storage_clone(const struct sock *sk, struct sock *newsk)
 		}
 
 		if (new_sk_storage) {
-			bpf_selem_link_map(smap, copy_selem);
+			ret = bpf_selem_link_map(smap, copy_selem);
+			if (ret)
+				goto out;
 			bpf_selem_link_storage_nolock(new_sk_storage, copy_selem);
 		} else {
 			ret = bpf_local_storage_alloc(newsk, smap, copy_selem, GFP_ATOMIC);
-- 
2.47.3