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>

1 files changed, 76 insertions, 38 deletions

diff --git a/net/netlink/genetlink.c b/net/netlink/genetlink.c
index 5a55be3f17a5..2f72598dd8fe 100644
--- 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,
         };