genl: Allow concurrent genl callbacks.

All genl callbacks are serialized by genl-mutex. This can become
bottleneck in multi threaded case.
Following patch adds an parameter to genl_family so that a
particular family can get concurrent netlink callback without
genl_lock held.
New rw-sem is used to protect genl callback from genl family unregister.
in case of parallel_ops genl-family read-lock is taken for callbacks and
write lock is taken for register or unregistration for any family.
In case of locked genl family semaphore and gel-mutex is locked for
any openration.

Signed-off-by: Pravin B Shelar <pshelar@nicira.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/net/genetlink.h b/include/net/genetlink.h
index bdfbe68..93024a4 100644 (file)
--- a/include/net/genetlink.h
+++ b/include/net/genetlink.h
@@ -50,6 +50,7 @@ struct genl_family {
        unsigned int            version;
        unsigned int            maxattr;
        bool                    netnsok;
+       bool                    parallel_ops;
        int                     (*pre_doit)(struct genl_ops *ops,
                                            struct sk_buff *skb,
                                            struct genl_info *info);

diff --git a/net/netlink/genetlink.c b/net/netlink/genetlink.c
index 5a55be3..2f72598 100644 (file)
--- a/net/netlink/genetlink.c
+++ b/net/netlink/genetlink.c
@@ -16,10 +16,12 @@
 #include <linux/skbuff.h>
 #include <linux/mutex.h>
 #include <linux/bitmap.h>
+#include <linux/rwsem.h>
 #include <net/sock.h>
 #include <net/genetlink.h>
 
 static DEFINE_MUTEX(genl_mutex); /* serialization of message processing */
+static DECLARE_RWSEM(cb_lock);
 
 void genl_lock(void)
 {
@@ -41,6 +43,18 @@ int lockdep_genl_is_held(void)
 EXPORT_SYMBOL(lockdep_genl_is_held);
 #endif
 
+static void genl_lock_all(void)
+{
+       down_write(&cb_lock);
+       genl_lock();
+}
+
+static void genl_unlock_all(void)
+{
+       genl_unlock();
+       up_write(&cb_lock);
+}
+
 #define GENL_FAM_TAB_SIZE      16
 #define GENL_FAM_TAB_MASK      (GENL_FAM_TAB_SIZE - 1)
 
@@ -144,7 +158,7 @@ int genl_register_mc_group(struct genl_family *family,
        BUG_ON(grp->name[0] == '\0');
        BUG_ON(memchr(grp->name, '\0', GENL_NAMSIZ) == NULL);
 
-       genl_lock();
+       genl_lock_all();
 
        /* special-case our own group */
        if (grp == &notify_grp)
@@ -213,7 +227,7 @@ int genl_register_mc_group(struct genl_family *family,
 
        genl_ctrl_event(CTRL_CMD_NEWMCAST_GRP, grp);
  out:
-       genl_unlock();
+       genl_unlock_all();
        return err;
 }
 EXPORT_SYMBOL(genl_register_mc_group);
@@ -255,9 +269,9 @@ static void __genl_unregister_mc_group(struct genl_family *family,
 void genl_unregister_mc_group(struct genl_family *family,
                              struct genl_multicast_group *grp)
 {
-       genl_lock();
+       genl_lock_all();
        __genl_unregister_mc_group(family, grp);
-       genl_unlock();
+       genl_unlock_all();
 }
 EXPORT_SYMBOL(genl_unregister_mc_group);
 
@@ -303,9 +317,9 @@ int genl_register_ops(struct genl_family *family, struct genl_ops *ops)
        if (ops->policy)
                ops->flags |= GENL_CMD_CAP_HASPOL;
 
-       genl_lock();
+       genl_lock_all();
        list_add_tail(&ops->ops_list, &family->ops_list);
-       genl_unlock();
+       genl_unlock_all();
 
        genl_ctrl_event(CTRL_CMD_NEWOPS, ops);
        err = 0;
@@ -334,16 +348,16 @@ int genl_unregister_ops(struct genl_family *family, struct genl_ops *ops)
 {
        struct genl_ops *rc;
 
-       genl_lock();
+       genl_lock_all();
        list_for_each_entry(rc, &family->ops_list, ops_list) {
                if (rc == ops) {
                        list_del(&ops->ops_list);
-                       genl_unlock();
+                       genl_unlock_all();
                        genl_ctrl_event(CTRL_CMD_DELOPS, ops);
                        return 0;
                }
        }
-       genl_unlock();
+       genl_unlock_all();
 
        return -ENOENT;
 }
@@ -373,7 +387,7 @@ int genl_register_family(struct genl_family *family)
        INIT_LIST_HEAD(&family->ops_list);
        INIT_LIST_HEAD(&family->mcast_groups);
 
-       genl_lock();
+       genl_lock_all();
 
        if (genl_family_find_byname(family->name)) {
                err = -EEXIST;
@@ -394,7 +408,7 @@ int genl_register_family(struct genl_family *family)
                goto errout_locked;
        }
 
-       if (family->maxattr) {
+       if (family->maxattr && !family->parallel_ops) {
                family->attrbuf = kmalloc((family->maxattr+1) *
                                        sizeof(struct nlattr *), GFP_KERNEL);
                if (family->attrbuf == NULL) {
@@ -405,14 +419,14 @@ int genl_register_family(struct genl_family *family)
                family->attrbuf = NULL;
 
        list_add_tail(&family->family_list, genl_family_chain(family->id));
-       genl_unlock();
+       genl_unlock_all();
 
        genl_ctrl_event(CTRL_CMD_NEWFAMILY, family);
 
        return 0;
 
 errout_locked:
-       genl_unlock();
+       genl_unlock_all();
 errout:
        return err;
 }
@@ -476,7 +490,7 @@ int genl_unregister_family(struct genl_family *family)
 {
        struct genl_family *rc;
 
-       genl_lock();
+       genl_lock_all();
 
        genl_unregister_mc_groups(family);
 
@@ -486,14 +500,14 @@ int genl_unregister_family(struct genl_family *family)
 
                list_del(&rc->family_list);
                INIT_LIST_HEAD(&family->ops_list);
-               genl_unlock();
+               genl_unlock_all();
 
                kfree(family->attrbuf);
                genl_ctrl_event(CTRL_CMD_DELFAMILY, family);
                return 0;
        }
 
-       genl_unlock();
+       genl_unlock_all();
 
        return -ENOENT;
 }
@@ -530,19 +544,17 @@ void *genlmsg_put(struct sk_buff *skb, u32 portid, u32 seq,
 }
 EXPORT_SYMBOL(genlmsg_put);
 
-static int genl_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
+static int genl_family_rcv_msg(struct genl_family *family,
+                              struct sk_buff *skb,
+                              struct nlmsghdr *nlh)
 {
        struct genl_ops *ops;
-       struct genl_family *family;
        struct net *net = sock_net(skb->sk);
        struct genl_info info;
        struct genlmsghdr *hdr = nlmsg_data(nlh);
+       struct nlattr **attrbuf;
        int hdrlen, err;
 
-       family = genl_family_find_byid(nlh->nlmsg_type);
-       if (family == NULL)
-               return -ENOENT;
-
        /* this family doesn't exist in this netns */
        if (!family->netnsok && !net_eq(net, &init_net))
                return -ENOENT;
@@ -560,26 +572,30 @@ static int genl_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
                return -EPERM;
 
        if (nlh->nlmsg_flags & NLM_F_DUMP) {
+               struct netlink_dump_control c = {
+                       .dump = ops->dumpit,
+                       .done = ops->done,
+               };
+
                if (ops->dumpit == NULL)
                        return -EOPNOTSUPP;
 
-               genl_unlock();
-               {
-                       struct netlink_dump_control c = {
-                               .dump = ops->dumpit,
-                               .done = ops->done,
-                       };
-                       err = netlink_dump_start(net->genl_sock, skb, nlh, &c);
-               }
-               genl_lock();
-               return err;
+               return netlink_dump_start(net->genl_sock, skb, nlh, &c);
        }
 
        if (ops->doit == NULL)
                return -EOPNOTSUPP;
 
-       if (family->attrbuf) {
-               err = nlmsg_parse(nlh, hdrlen, family->attrbuf, family->maxattr,
+       if (family->maxattr && family->parallel_ops) {
+               attrbuf = kmalloc((family->maxattr+1) *
+                                       sizeof(struct nlattr *), GFP_KERNEL);
+               if (attrbuf == NULL)
+                       return -ENOMEM;
+       } else
+               attrbuf = family->attrbuf;
+
+       if (attrbuf) {
+               err = nlmsg_parse(nlh, hdrlen, attrbuf, family->maxattr,
                                  ops->policy);
                if (err < 0)
                        return err;
@@ -590,7 +606,7 @@ static int genl_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
        info.nlhdr = nlh;
        info.genlhdr = nlmsg_data(nlh);
        info.userhdr = nlmsg_data(nlh) + GENL_HDRLEN;
-       info.attrs = family->attrbuf;
+       info.attrs = attrbuf;
        genl_info_net_set(&info, net);
        memset(&info.user_ptr, 0, sizeof(info.user_ptr));
 
@@ -605,14 +621,37 @@ static int genl_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
        if (family->post_doit)
                family->post_doit(ops, skb, &info);
 
+       if (family->parallel_ops)
+               kfree(attrbuf);
+
+       return err;
+}
+
+static int genl_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
+{
+       struct genl_family *family;
+       int err;
+
+       family = genl_family_find_byid(nlh->nlmsg_type);
+       if (family == NULL)
+               return -ENOENT;
+
+       if (!family->parallel_ops)
+               genl_lock();
+
+       err = genl_family_rcv_msg(family, skb, nlh);
+
+       if (!family->parallel_ops)
+               genl_unlock();
+
        return err;
 }
 
 static void genl_rcv(struct sk_buff *skb)
 {
-       genl_lock();
+       down_read(&cb_lock);
        netlink_rcv_skb(skb, &genl_rcv_msg);
-       genl_unlock();
+       up_read(&cb_lock);
 }
 
 /**************************************************************************
@@ -918,7 +957,6 @@ static int __net_init genl_pernet_init(struct net *net)
 {
        struct netlink_kernel_cfg cfg = {
                .input          = genl_rcv,
-               .cb_mutex       = &genl_mutex,
                .flags          = NL_CFG_F_NONROOT_RECV,
        };