[PATCH net-next] net: net->nsid_lock does not need BH safety

[PATCH net-next] net: net->nsid_lock does not need BH safety

[Eric Dumazet]

At the time of commit bc51dddf98c9 ("netns: avoid disabling irq
for netns id") peernet2id() was not yet using RCU.

Commit 2dce224f469f ("netns: protect netns
ID lookups with RCU") changed peernet2id() to no longer
acquire net->nsid_lock (potentially from BH context).

We do not need to block soft interrupts when acquiring
net->nsid_lock anymore.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Guillaume Nault <gnault@redhat.com>
Cc: Cong Wang <xiyou.wangcong@gmail.com>
---
 net/core/net_namespace.c | 22 +++++++++++-----------
 1 file changed, 11 insertions(+), 11 deletions(-)

diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c
index d0f607507ee8d0b6d31f11a49421b5f0a985bd3b..419604d9cf32e2e2a9af59dfef1fbcc7fab81e20 100644
--- a/net/core/net_namespace.c
+++ b/net/core/net_namespace.c
@@ -319,10 +319,10 @@ int peernet2id_alloc(struct net *net, struct net *peer, gfp_t gfp)
 	if (refcount_read(&net->ns.count) == 0)
 		return NETNSA_NSID_NOT_ASSIGNED;
 
-	spin_lock_bh(&net->nsid_lock);
+	spin_lock(&net->nsid_lock);
 	id = __peernet2id(net, peer);
 	if (id >= 0) {
-		spin_unlock_bh(&net->nsid_lock);
+		spin_unlock(&net->nsid_lock);
 		return id;
 	}
 
@@ -332,12 +332,12 @@ int peernet2id_alloc(struct net *net, struct net *peer, gfp_t gfp)
 	 * just been idr_remove()'d from there in cleanup_net().
 	 */
 	if (!maybe_get_net(peer)) {
-		spin_unlock_bh(&net->nsid_lock);
+		spin_unlock(&net->nsid_lock);
 		return NETNSA_NSID_NOT_ASSIGNED;
 	}
 
 	id = alloc_netid(net, peer, -1);
-	spin_unlock_bh(&net->nsid_lock);
+	spin_unlock(&net->nsid_lock);
 
 	put_net(peer);
 	if (id < 0)
@@ -628,20 +628,20 @@ static void unhash_nsid(struct net *net, struct net *last)
 	for_each_net(tmp) {
 		int id;
 
-		spin_lock_bh(&tmp->nsid_lock);
+		spin_lock(&tmp->nsid_lock);
 		id = __peernet2id(tmp, net);
 		if (id >= 0)
 			idr_remove(&tmp->netns_ids, id);
-		spin_unlock_bh(&tmp->nsid_lock);
+		spin_unlock(&tmp->nsid_lock);
 		if (id >= 0)
 			rtnl_net_notifyid(tmp, RTM_DELNSID, id, 0, NULL,
 					  GFP_KERNEL);
 		if (tmp == last)
 			break;
 	}
-	spin_lock_bh(&net->nsid_lock);
+	spin_lock(&net->nsid_lock);
 	idr_destroy(&net->netns_ids);
-	spin_unlock_bh(&net->nsid_lock);
+	spin_unlock(&net->nsid_lock);
 }
 
 static LLIST_HEAD(cleanup_list);
@@ -880,9 +880,9 @@ static int rtnl_net_newid(struct sk_buff *skb, struct nlmsghdr *nlh,
 		return PTR_ERR(peer);
 	}
 
-	spin_lock_bh(&net->nsid_lock);
+	spin_lock(&net->nsid_lock);
 	if (__peernet2id(net, peer) >= 0) {
-		spin_unlock_bh(&net->nsid_lock);
+		spin_unlock(&net->nsid_lock);
 		err = -EEXIST;
 		NL_SET_BAD_ATTR(extack, nla);
 		NL_SET_ERR_MSG(extack,
@@ -891,7 +891,7 @@ static int rtnl_net_newid(struct sk_buff *skb, struct nlmsghdr *nlh,
 	}
 
 	err = alloc_netid(net, peer, nsid);
-	spin_unlock_bh(&net->nsid_lock);
+	spin_unlock(&net->nsid_lock);
 	if (err >= 0) {
 		rtnl_net_notifyid(net, RTM_NEWNSID, err, NETLINK_CB(skb).portid,
 				  nlh, GFP_KERNEL);
-- 
2.50.0.727.gbf7dc18ff4-goog

Re: [PATCH net-next] net: net->nsid_lock does not need BH safety

[Kuniyuki Iwashima]

On Fri, Jun 27, 2025 at 9:32 AM Eric Dumazet <edumazet@google.com> wrote:
>
> At the time of commit bc51dddf98c9 ("netns: avoid disabling irq
> for netns id") peernet2id() was not yet using RCU.
>
> Commit 2dce224f469f ("netns: protect netns
> ID lookups with RCU") changed peernet2id() to no longer
> acquire net->nsid_lock (potentially from BH context).
>
> We do not need to block soft interrupts when acquiring
> net->nsid_lock anymore.
>
> Signed-off-by: Eric Dumazet <edumazet@google.com>

Reviewed-by: Kuniyuki Iwashima <kuniyu@google.com>

Re: [PATCH net-next] net: net->nsid_lock does not need BH safety

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net-next.git (main)
by Jakub Kicinski <kuba@kernel.org>:

On Fri, 27 Jun 2025 16:32:42 +0000 you wrote:
> At the time of commit bc51dddf98c9 ("netns: avoid disabling irq
> for netns id") peernet2id() was not yet using RCU.
> 
> Commit 2dce224f469f ("netns: protect netns
> ID lookups with RCU") changed peernet2id() to no longer
> acquire net->nsid_lock (potentially from BH context).
> 
> [...]

Here is the summary with links:
  - [net-next] net: net->nsid_lock does not need BH safety
    https://git.kernel.org/netdev/net-next/c/aed4969f2bdf

You are awesome, thank you!
-- 
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