From: Nicolas Dichtel Date: Thu, 7 May 2015 09:02:51 +0000 (+0200) Subject: netns: use a spin_lock to protect nsid management X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=95f38411df055a0ecefe3a3d119d98241087d5ca;p=GitHub%2Fmoto-9609%2Fandroid_kernel_motorola_exynos9610.git netns: use a spin_lock to protect nsid management Before this patch, nsid were protected by the rtnl lock. The goal of this patch is to be able to find a nsid without needing to hold the rtnl lock. The next patch will introduce a netlink socket option to listen to all netns that have a nsid assigned into the netns where the socket is opened. Thus, it's important to call rtnl_net_notifyid() outside the spinlock, to avoid a recursive lock (nsid are notified via rtnl). This was the main reason of the previous patch. Signed-off-by: Nicolas Dichtel Signed-off-by: David S. Miller --- diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c index ee864241f8d6..ae5008b097de 100644 --- a/net/core/net_namespace.c +++ b/net/core/net_namespace.c @@ -28,6 +28,7 @@ static LIST_HEAD(pernet_list); static struct list_head *first_device = &pernet_list; DEFINE_MUTEX(net_mutex); +static DEFINE_SPINLOCK(nsid_lock); LIST_HEAD(net_namespace_list); EXPORT_SYMBOL_GPL(net_namespace_list); @@ -147,18 +148,17 @@ static void ops_free_list(const struct pernet_operations *ops, } } +/* should be called with nsid_lock held */ static int alloc_netid(struct net *net, struct net *peer, int reqid) { int min = 0, max = 0; - ASSERT_RTNL(); - if (reqid >= 0) { min = reqid; max = reqid + 1; } - return idr_alloc(&net->netns_ids, peer, min, max, GFP_KERNEL); + return idr_alloc(&net->netns_ids, peer, min, max, GFP_ATOMIC); } /* This function is used by idr_for_each(). If net is equal to peer, the @@ -174,13 +174,15 @@ static int net_eq_idr(int id, void *net, void *peer) return 0; } +/* Should be called with nsid_lock held. If a new id is assigned, the bool alloc + * is set to true, thus the caller knows that the new id must be notified via + * rtnl. + */ static int __peernet2id_alloc(struct net *net, struct net *peer, bool *alloc) { int id = idr_for_each(&net->netns_ids, net_eq_idr, peer); bool alloc_it = *alloc; - ASSERT_RTNL(); - *alloc = false; /* Magic value for id 0. */ @@ -198,6 +200,7 @@ static int __peernet2id_alloc(struct net *net, struct net *peer, bool *alloc) return NETNSA_NSID_NOT_ASSIGNED; } +/* should be called with nsid_lock held */ static int __peernet2id(struct net *net, struct net *peer) { bool no = false; @@ -211,27 +214,46 @@ static void rtnl_net_notifyid(struct net *net, int cmd, int id); */ int peernet2id_alloc(struct net *net, struct net *peer) { - bool alloc = atomic_read(&peer->count) == 0 ? false : true; + unsigned long flags; + bool alloc; int id; + spin_lock_irqsave(&nsid_lock, flags); + alloc = atomic_read(&peer->count) == 0 ? false : true; id = __peernet2id_alloc(net, peer, &alloc); + spin_unlock_irqrestore(&nsid_lock, flags); if (alloc && id >= 0) rtnl_net_notifyid(net, RTM_NEWNSID, id); return id; } EXPORT_SYMBOL(peernet2id_alloc); +/* This function returns, if assigned, the id of a peer netns. */ +static int peernet2id(struct net *net, struct net *peer) +{ + unsigned long flags; + int id; + + spin_lock_irqsave(&nsid_lock, flags); + id = __peernet2id(net, peer); + spin_unlock_irqrestore(&nsid_lock, flags); + return id; +} + struct net *get_net_ns_by_id(struct net *net, int id) { + unsigned long flags; struct net *peer; if (id < 0) return NULL; rcu_read_lock(); + spin_lock_irqsave(&nsid_lock, flags); peer = idr_find(&net->netns_ids, id); if (peer) get_net(peer); + spin_unlock_irqrestore(&nsid_lock, flags); rcu_read_unlock(); return peer; @@ -372,14 +394,19 @@ static void cleanup_net(struct work_struct *work) list_del_rcu(&net->list); list_add_tail(&net->exit_list, &net_exit_list); for_each_net(tmp) { - int id = __peernet2id(tmp, net); + int id; - if (id >= 0) { - rtnl_net_notifyid(tmp, RTM_DELNSID, id); + spin_lock_irq(&nsid_lock); + id = __peernet2id(tmp, net); + if (id >= 0) idr_remove(&tmp->netns_ids, id); - } + spin_unlock_irq(&nsid_lock); + if (id >= 0) + rtnl_net_notifyid(tmp, RTM_DELNSID, id); } + spin_lock_irq(&nsid_lock); idr_destroy(&net->netns_ids); + spin_unlock_irq(&nsid_lock); } rtnl_unlock(); @@ -507,6 +534,7 @@ static int rtnl_net_newid(struct sk_buff *skb, struct nlmsghdr *nlh) { struct net *net = sock_net(skb->sk); struct nlattr *tb[NETNSA_MAX + 1]; + unsigned long flags; struct net *peer; int nsid, err; @@ -527,12 +555,14 @@ static int rtnl_net_newid(struct sk_buff *skb, struct nlmsghdr *nlh) if (IS_ERR(peer)) return PTR_ERR(peer); + spin_lock_irqsave(&nsid_lock, flags); if (__peernet2id(net, peer) >= 0) { err = -EEXIST; goto out; } err = alloc_netid(net, peer, nsid); + spin_unlock_irqrestore(&nsid_lock, flags); if (err >= 0) { rtnl_net_notifyid(net, RTM_NEWNSID, err); err = 0; @@ -601,7 +631,7 @@ static int rtnl_net_getid(struct sk_buff *skb, struct nlmsghdr *nlh) goto out; } - id = __peernet2id(net, peer); + id = peernet2id(net, peer); err = rtnl_net_fill(msg, NETLINK_CB(skb).portid, nlh->nlmsg_seq, 0, RTM_GETNSID, net, id); if (err < 0) @@ -654,10 +684,11 @@ static int rtnl_net_dumpid(struct sk_buff *skb, struct netlink_callback *cb) .idx = 0, .s_idx = cb->args[0], }; + unsigned long flags; - ASSERT_RTNL(); - + spin_lock_irqsave(&nsid_lock, flags); idr_for_each(&net->netns_ids, rtnl_net_dumpid_one, &net_cb); + spin_unlock_irqrestore(&nsid_lock, flags); cb->args[0] = net_cb.idx; return skb->len;