genetlink: use idr to track families

Since generic netlink family IDs are small integers, allocated
densely, IDR is an ideal match for lookups. Replace the existing
hand-written hash-table with IDR for allocation and lookup.

This lets the families only be written to once, during register,
since the list_head can be removed and removal of a family won't
cause any writes.

It also slightly reduces the code size (by about 1.3k on x86-64).

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/net/genetlink.h b/include/net/genetlink.h
index 2298b50..3ec87ba 100644 (file)
--- a/include/net/genetlink.h
+++ b/include/net/genetlink.h
@@ -40,7 +40,6 @@ struct genl_info;
  *     generic netlink family is removed while there are still open
  *     sockets.
  * @attrbuf: buffer to store parsed attributes (private)
- * @family_list: family list (private)
  * @mcgrps: multicast groups used by this family
  * @n_mcgrps: number of multicast groups
  * @mcgrp_offset: starting number of multicast group IDs in this family
@@ -70,11 +69,10 @@ struct genl_family {
        unsigned int            n_ops;
        unsigned int            n_mcgrps;
        unsigned int            mcgrp_offset;   /* private */
-       struct list_head        family_list;    /* private */
        struct module           *module;
 };
 
-struct nlattr **genl_family_attrbuf(struct genl_family *family);
+struct nlattr **genl_family_attrbuf(const struct genl_family *family);
 
 /**
  * struct genl_info - receiving information
@@ -134,12 +132,12 @@ struct genl_ops {
 };
 
 int genl_register_family(struct genl_family *family);
-int genl_unregister_family(struct genl_family *family);
-void genl_notify(struct genl_family *family, struct sk_buff *skb,
+int genl_unregister_family(const struct genl_family *family);
+void genl_notify(const struct genl_family *family, struct sk_buff *skb,
                 struct genl_info *info, u32 group, gfp_t flags);
 
 void *genlmsg_put(struct sk_buff *skb, u32 portid, u32 seq,
-                 struct genl_family *family, int flags, u8 cmd);
+                 const struct genl_family *family, int flags, u8 cmd);
 
 /**
  * genlmsg_nlhdr - Obtain netlink header from user specified header
@@ -148,8 +146,8 @@ void *genlmsg_put(struct sk_buff *skb, u32 portid, u32 seq,
  *
  * Returns pointer to netlink header.
  */
-static inline struct nlmsghdr *genlmsg_nlhdr(void *user_hdr,
-                                            struct genl_family *family)
+static inline struct nlmsghdr *
+genlmsg_nlhdr(void *user_hdr, const struct genl_family *family)
 {
        return (struct nlmsghdr *)((char *)user_hdr -
                                   family->hdrsize -
@@ -185,7 +183,7 @@ static inline int genlmsg_parse(const struct nlmsghdr *nlh,
  */
 static inline void genl_dump_check_consistent(struct netlink_callback *cb,
                                              void *user_hdr,
-                                             struct genl_family *family)
+                                             const struct genl_family *family)
 {
        nl_dump_check_consistent(cb, genlmsg_nlhdr(user_hdr, family));
 }
@@ -202,7 +200,7 @@ static inline void genl_dump_check_consistent(struct netlink_callback *cb,
  */
 static inline void *genlmsg_put_reply(struct sk_buff *skb,
                                      struct genl_info *info,
-                                     struct genl_family *family,
+                                     const struct genl_family *family,
                                      int flags, u8 cmd)
 {
        return genlmsg_put(skb, info->snd_portid, info->snd_seq, family,
@@ -239,7 +237,7 @@ static inline void genlmsg_cancel(struct sk_buff *skb, void *hdr)
  * @group: offset of multicast group in groups array
  * @flags: allocation flags
  */
-static inline int genlmsg_multicast_netns(struct genl_family *family,
+static inline int genlmsg_multicast_netns(const struct genl_family *family,
                                          struct net *net, struct sk_buff *skb,
                                          u32 portid, unsigned int group, gfp_t flags)
 {
@@ -257,7 +255,7 @@ static inline int genlmsg_multicast_netns(struct genl_family *family,
  * @group: offset of multicast group in groups array
  * @flags: allocation flags
  */
-static inline int genlmsg_multicast(struct genl_family *family,
+static inline int genlmsg_multicast(const struct genl_family *family,
                                    struct sk_buff *skb, u32 portid,
                                    unsigned int group, gfp_t flags)
 {
@@ -275,7 +273,7 @@ static inline int genlmsg_multicast(struct genl_family *family,
  *
  * This function must hold the RTNL or rcu_read_lock().
  */
-int genlmsg_multicast_allns(struct genl_family *family,
+int genlmsg_multicast_allns(const struct genl_family *family,
                            struct sk_buff *skb, u32 portid,
                            unsigned int group, gfp_t flags);
 
@@ -359,8 +357,9 @@ static inline struct sk_buff *genlmsg_new(size_t payload, gfp_t flags)
  * This function returns the number of broadcast listeners that have set the
  * NETLINK_RECV_NO_ENOBUFS socket option.
  */
-static inline int genl_set_err(struct genl_family *family, struct net *net,
-                              u32 portid, u32 group, int code)
+static inline int genl_set_err(const struct genl_family *family,
+                              struct net *net, u32 portid,
+                              u32 group, int code)
 {
        if (WARN_ON_ONCE(group >= family->n_mcgrps))
                return -EINVAL;
@@ -368,7 +367,7 @@ static inline int genl_set_err(struct genl_family *family, struct net *net,
        return netlink_set_err(net->genl_sock, portid, group, code);
 }
 
-static inline int genl_has_listeners(struct genl_family *family,
+static inline int genl_has_listeners(const struct genl_family *family,
                                     struct net *net, unsigned int group)
 {
        if (WARN_ON_ONCE(group >= family->n_mcgrps))

diff --git a/include/uapi/linux/genetlink.h b/include/uapi/linux/genetlink.h
index d9b2db4..adc8993 100644 (file)
--- a/include/uapi/linux/genetlink.h
+++ b/include/uapi/linux/genetlink.h
@@ -29,6 +29,8 @@ struct genlmsghdr {
 #define GENL_ID_CTRL           NLMSG_MIN_TYPE
 #define GENL_ID_VFS_DQUOT      (NLMSG_MIN_TYPE + 1)
 #define GENL_ID_PMCRAID                (NLMSG_MIN_TYPE + 2)
+/* must be last reserved + 1 */
+#define GENL_START_ALLOC       (NLMSG_MIN_TYPE + 3)
 
 /**************************************************************************
  * Controller

diff --git a/net/netlink/genetlink.c b/net/netlink/genetlink.c
index ca582ee..8565992 100644 (file)
--- a/net/netlink/genetlink.c
+++ b/net/netlink/genetlink.c
@@ -17,6 +17,7 @@
 #include <linux/mutex.h>
 #include <linux/bitmap.h>
 #include <linux/rwsem.h>
+#include <linux/idr.h>
 #include <net/sock.h>
 #include <net/genetlink.h>
 
@@ -58,10 +59,8 @@ static void genl_unlock_all(void)
        up_write(&cb_lock);
 }
 
-#define GENL_FAM_TAB_SIZE      16
-#define GENL_FAM_TAB_MASK      (GENL_FAM_TAB_SIZE - 1)
+static DEFINE_IDR(genl_fam_idr);
 
-static struct list_head family_ht[GENL_FAM_TAB_SIZE];
 /*
  * Bitmap of multicast groups that are currently in use.
  *
@@ -86,45 +85,29 @@ static unsigned long mc_group_start = 0x3 | BIT(GENL_ID_CTRL) |
 static unsigned long *mc_groups = &mc_group_start;
 static unsigned long mc_groups_longs = 1;
 
-static int genl_ctrl_event(int event, struct genl_family *family,
+static int genl_ctrl_event(int event, const struct genl_family *family,
                           const struct genl_multicast_group *grp,
                           int grp_id);
 
-static inline unsigned int genl_family_hash(unsigned int id)
+static const struct genl_family *genl_family_find_byid(unsigned int id)
 {
-       return id & GENL_FAM_TAB_MASK;
+       return idr_find(&genl_fam_idr, id);
 }
 
-static inline struct list_head *genl_family_chain(unsigned int id)
+static const struct genl_family *genl_family_find_byname(char *name)
 {
-       return &family_ht[genl_family_hash(id)];
-}
-
-static struct genl_family *genl_family_find_byid(unsigned int id)
-{
-       struct genl_family *f;
+       const struct genl_family *family;
+       unsigned int id;
 
-       list_for_each_entry(f, genl_family_chain(id), family_list)
-               if (f->id == id)
-                       return f;
+       idr_for_each_entry(&genl_fam_idr, family, id)
+               if (strcmp(family->name, name) == 0)
+                       return family;
 
        return NULL;
 }
 
-static struct genl_family *genl_family_find_byname(char *name)
-{
-       struct genl_family *f;
-       int i;
-
-       for (i = 0; i < GENL_FAM_TAB_SIZE; i++)
-               list_for_each_entry(f, genl_family_chain(i), family_list)
-                       if (strcmp(f->name, name) == 0)
-                               return f;
-
-       return NULL;
-}
-
-static const struct genl_ops *genl_get_cmd(u8 cmd, struct genl_family *family)
+static const struct genl_ops *genl_get_cmd(u8 cmd,
+                                          const struct genl_family *family)
 {
        int i;
 
@@ -135,26 +118,6 @@ static const struct genl_ops *genl_get_cmd(u8 cmd, struct genl_family *family)
        return NULL;
 }
 
-/* Of course we are going to have problems once we hit
- * 2^16 alive types, but that can only happen by year 2K
-*/
-static u16 genl_generate_id(void)
-{
-       static u16 id_gen_idx = GENL_MIN_ID;
-       int i;
-
-       for (i = 0; i <= GENL_MAX_ID - GENL_MIN_ID; i++) {
-               if (id_gen_idx != GENL_ID_VFS_DQUOT &&
-                   id_gen_idx != GENL_ID_PMCRAID &&
-                   !genl_family_find_byid(id_gen_idx))
-                       return id_gen_idx;
-               if (++id_gen_idx > GENL_MAX_ID)
-                       id_gen_idx = GENL_MIN_ID;
-       }
-
-       return 0;
-}
-
 static int genl_allocate_reserve_groups(int n_groups, int *first_id)
 {
        unsigned long *new_groups;
@@ -295,7 +258,7 @@ static int genl_validate_assign_mc_groups(struct genl_family *family)
        return err;
 }
 
-static void genl_unregister_mc_groups(struct genl_family *family)
+static void genl_unregister_mc_groups(const struct genl_family *family)
 {
        struct net *net;
        int i;
@@ -358,6 +321,7 @@ static int genl_validate_ops(const struct genl_family *family)
 int genl_register_family(struct genl_family *family)
 {
        int err, i;
+       int start = GENL_START_ALLOC, end = GENL_MAX_ID;
 
        err = genl_validate_ops(family);
        if (err)
@@ -370,34 +334,20 @@ int genl_register_family(struct genl_family *family)
                goto errout_locked;
        }
 
+       /*
+        * Sadly, a few cases need to be special-cased
+        * due to them having previously abused the API
+        * and having used their family ID also as their
+        * multicast group ID, so we use reserved IDs
+        * for both to be sure we can do that mapping.
+        */
        if (family == &genl_ctrl) {
-               family->id = GENL_ID_CTRL;
-       } else {
-               u16 newid;
-
-               /* this should be left zero in the struct */
-               WARN_ON(family->id);
-
-               /*
-                * Sadly, a few cases need to be special-cased
-                * due to them having previously abused the API
-                * and having used their family ID also as their
-                * multicast group ID, so we use reserved IDs
-                * for both to be sure we can do that mapping.
-                */
-               if (strcmp(family->name, "pmcraid") == 0)
-                       newid = GENL_ID_PMCRAID;
-               else if (strcmp(family->name, "VFS_DQUOT") == 0)
-                       newid = GENL_ID_VFS_DQUOT;
-               else
-                       newid = genl_generate_id();
-
-               if (!newid) {
-                       err = -ENOMEM;
-                       goto errout_locked;
-               }
-
-               family->id = newid;
+               /* and this needs to be special for initial family lookups */
+               start = end = GENL_ID_CTRL;
+       } else if (strcmp(family->name, "pmcraid") == 0) {
+               start = end = GENL_ID_PMCRAID;
+       } else if (strcmp(family->name, "VFS_DQUOT") == 0) {
+               start = end = GENL_ID_VFS_DQUOT;
        }
 
        if (family->maxattr && !family->parallel_ops) {
@@ -410,11 +360,15 @@ int genl_register_family(struct genl_family *family)
        } else
                family->attrbuf = NULL;
 
+       family->id = idr_alloc(&genl_fam_idr, family,
+                              start, end + 1, GFP_KERNEL);
+       if (!family->id)
+               goto errout_locked;
+
        err = genl_validate_assign_mc_groups(family);
        if (err)
-               goto errout_locked;
+               goto errout_remove;
 
-       list_add_tail(&family->family_list, genl_family_chain(family->id));
        genl_unlock_all();
 
        /* send all events */
@@ -425,6 +379,8 @@ int genl_register_family(struct genl_family *family)
 
        return 0;
 
+errout_remove:
+       idr_remove(&genl_fam_idr, family->id);
 errout_locked:
        genl_unlock_all();
        return err;
@@ -439,32 +395,29 @@ EXPORT_SYMBOL(genl_register_family);
  *
  * Returns 0 on success or a negative error code.
  */
-int genl_unregister_family(struct genl_family *family)
+int genl_unregister_family(const struct genl_family *family)
 {
-       struct genl_family *rc;
-
        genl_lock_all();
 
-       list_for_each_entry(rc, genl_family_chain(family->id), family_list) {
-               if (family->id != rc->id || strcmp(rc->name, family->name))
-                       continue;
+       if (genl_family_find_byid(family->id)) {
+               genl_unlock_all();
+               return -ENOENT;
+       }
 
-               genl_unregister_mc_groups(family);
+       genl_unregister_mc_groups(family);
 
-               list_del(&rc->family_list);
-               up_write(&cb_lock);
-               wait_event(genl_sk_destructing_waitq,
-                          atomic_read(&genl_sk_destructing_cnt) == 0);
-               genl_unlock();
+       idr_remove(&genl_fam_idr, family->id);
 
-               kfree(family->attrbuf);
-               genl_ctrl_event(CTRL_CMD_DELFAMILY, family, NULL, 0);
-               return 0;
-       }
+       up_write(&cb_lock);
+       wait_event(genl_sk_destructing_waitq,
+                  atomic_read(&genl_sk_destructing_cnt) == 0);
+       genl_unlock();
 
-       genl_unlock_all();
+       kfree(family->attrbuf);
 
-       return -ENOENT;
+       genl_ctrl_event(CTRL_CMD_DELFAMILY, family, NULL, 0);
+
+       return 0;
 }
 EXPORT_SYMBOL(genl_unregister_family);
 
@@ -480,7 +433,7 @@ EXPORT_SYMBOL(genl_unregister_family);
  * Returns pointer to user specific header
  */
 void *genlmsg_put(struct sk_buff *skb, u32 portid, u32 seq,
-                               struct genl_family *family, int flags, u8 cmd)
+                 const struct genl_family *family, int flags, u8 cmd)
 {
        struct nlmsghdr *nlh;
        struct genlmsghdr *hdr;
@@ -539,7 +492,7 @@ static int genl_lock_done(struct netlink_callback *cb)
        return rc;
 }
 
-static int genl_family_rcv_msg(struct genl_family *family,
+static int genl_family_rcv_msg(const struct genl_family *family,
                               struct sk_buff *skb,
                               struct nlmsghdr *nlh)
 {
@@ -651,7 +604,7 @@ out:
 
 static int genl_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
 {
-       struct genl_family *family;
+       const struct genl_family *family;
        int err;
 
        family = genl_family_find_byid(nlh->nlmsg_type);
@@ -682,7 +635,7 @@ static void genl_rcv(struct sk_buff *skb)
 
 static struct genl_family genl_ctrl;
 
-static int ctrl_fill_info(struct genl_family *family, u32 portid, u32 seq,
+static int ctrl_fill_info(const struct genl_family *family, u32 portid, u32 seq,
                          u32 flags, struct sk_buff *skb, u8 cmd)
 {
        void *hdr;
@@ -769,7 +722,7 @@ nla_put_failure:
        return -EMSGSIZE;
 }
 
-static int ctrl_fill_mcgrp_info(struct genl_family *family,
+static int ctrl_fill_mcgrp_info(const struct genl_family *family,
                                const struct genl_multicast_group *grp,
                                int grp_id, u32 portid, u32 seq, u32 flags,
                                struct sk_buff *skb, u8 cmd)
@@ -812,37 +765,30 @@ nla_put_failure:
 
 static int ctrl_dumpfamily(struct sk_buff *skb, struct netlink_callback *cb)
 {
-
-       int i, n = 0;
+       int n = 0;
        struct genl_family *rt;
        struct net *net = sock_net(skb->sk);
-       int chains_to_skip = cb->args[0];
-       int fams_to_skip = cb->args[1];
-
-       for (i = chains_to_skip; i < GENL_FAM_TAB_SIZE; i++) {
-               n = 0;
-               list_for_each_entry(rt, genl_family_chain(i), family_list) {
-                       if (!rt->netnsok && !net_eq(net, &init_net))
-                               continue;
-                       if (++n < fams_to_skip)
-                               continue;
-                       if (ctrl_fill_info(rt, NETLINK_CB(cb->skb).portid,
-                                          cb->nlh->nlmsg_seq, NLM_F_MULTI,
-                                          skb, CTRL_CMD_NEWFAMILY) < 0)
-                               goto errout;
-               }
+       int fams_to_skip = cb->args[0];
+       unsigned int id;
 
-               fams_to_skip = 0;
-       }
+       idr_for_each_entry(&genl_fam_idr, rt, id) {
+               if (!rt->netnsok && !net_eq(net, &init_net))
+                       continue;
+
+               if (n++ < fams_to_skip)
+                       continue;
 
-errout:
-       cb->args[0] = i;
-       cb->args[1] = n;
+               if (ctrl_fill_info(rt, NETLINK_CB(cb->skb).portid,
+                                  cb->nlh->nlmsg_seq, NLM_F_MULTI,
+                                  skb, CTRL_CMD_NEWFAMILY) < 0)
+                       break;
+       }
 
+       cb->args[0] = n;
        return skb->len;
 }
 
-static struct sk_buff *ctrl_build_family_msg(struct genl_family *family,
+static struct sk_buff *ctrl_build_family_msg(const struct genl_family *family,
                                             u32 portid, int seq, u8 cmd)
 {
        struct sk_buff *skb;
@@ -862,7 +808,7 @@ static struct sk_buff *ctrl_build_family_msg(struct genl_family *family,
 }
 
 static struct sk_buff *
-ctrl_build_mcgrp_msg(struct genl_family *family,
+ctrl_build_mcgrp_msg(const struct genl_family *family,
                     const struct genl_multicast_group *grp,
                     int grp_id, u32 portid, int seq, u8 cmd)
 {
@@ -892,7 +838,7 @@ static const struct nla_policy ctrl_policy[CTRL_ATTR_MAX+1] = {
 static int ctrl_getfamily(struct sk_buff *skb, struct genl_info *info)
 {
        struct sk_buff *msg;
-       struct genl_family *res = NULL;
+       const struct genl_family *res = NULL;
        int err = -EINVAL;
 
        if (info->attrs[CTRL_ATTR_FAMILY_ID]) {
@@ -936,7 +882,7 @@ static int ctrl_getfamily(struct sk_buff *skb, struct genl_info *info)
        return genlmsg_reply(msg, info);
 }
 
-static int genl_ctrl_event(int event, struct genl_family *family,
+static int genl_ctrl_event(int event, const struct genl_family *family,
                           const struct genl_multicast_group *grp,
                           int grp_id)
 {
@@ -1005,25 +951,24 @@ static struct genl_family genl_ctrl = {
 
 static int genl_bind(struct net *net, int group)
 {
-       int i, err = -ENOENT;
+       struct genl_family *f;
+       int err = -ENOENT;
+       unsigned int id;
 
        down_read(&cb_lock);
-       for (i = 0; i < GENL_FAM_TAB_SIZE; i++) {
-               struct genl_family *f;
-
-               list_for_each_entry(f, genl_family_chain(i), family_list) {
-                       if (group >= f->mcgrp_offset &&
-                           group < f->mcgrp_offset + f->n_mcgrps) {
-                               int fam_grp = group - f->mcgrp_offset;
-
-                               if (!f->netnsok && net != &init_net)
-                                       err = -ENOENT;
-                               else if (f->mcast_bind)
-                                       err = f->mcast_bind(net, fam_grp);
-                               else
-                                       err = 0;
-                               break;
-                       }
+
+       idr_for_each_entry(&genl_fam_idr, f, id) {
+               if (group >= f->mcgrp_offset &&
+                   group < f->mcgrp_offset + f->n_mcgrps) {
+                       int fam_grp = group - f->mcgrp_offset;
+
+                       if (!f->netnsok && net != &init_net)
+                               err = -ENOENT;
+                       else if (f->mcast_bind)
+                               err = f->mcast_bind(net, fam_grp);
+                       else
+                               err = 0;
+                       break;
                }
        }
        up_read(&cb_lock);
@@ -1033,21 +978,19 @@ static int genl_bind(struct net *net, int group)
 
 static void genl_unbind(struct net *net, int group)
 {
-       int i;
+       struct genl_family *f;
+       unsigned int id;
 
        down_read(&cb_lock);
-       for (i = 0; i < GENL_FAM_TAB_SIZE; i++) {
-               struct genl_family *f;
 
-               list_for_each_entry(f, genl_family_chain(i), family_list) {
-                       if (group >= f->mcgrp_offset &&
-                           group < f->mcgrp_offset + f->n_mcgrps) {
-                               int fam_grp = group - f->mcgrp_offset;
+       idr_for_each_entry(&genl_fam_idr, f, id) {
+               if (group >= f->mcgrp_offset &&
+                   group < f->mcgrp_offset + f->n_mcgrps) {
+                       int fam_grp = group - f->mcgrp_offset;
 
-                               if (f->mcast_unbind)
-                                       f->mcast_unbind(net, fam_grp);
-                               break;
-                       }
+                       if (f->mcast_unbind)
+                               f->mcast_unbind(net, fam_grp);
+                       break;
                }
        }
        up_read(&cb_lock);
@@ -1087,10 +1030,7 @@ static struct pernet_operations genl_pernet_ops = {
 
 static int __init genl_init(void)
 {
-       int i, err;
-
-       for (i = 0; i < GENL_FAM_TAB_SIZE; i++)
-               INIT_LIST_HEAD(&family_ht[i]);
+       int err;
 
        err = genl_register_family(&genl_ctrl);
        if (err < 0)
@@ -1118,7 +1058,7 @@ subsys_initcall(genl_init);
  * You cannot use this function with a family that has parallel_ops
  * and you can only use it within (pre/post) doit/dumpit callbacks.
  */
-struct nlattr **genl_family_attrbuf(struct genl_family *family)
+struct nlattr **genl_family_attrbuf(const struct genl_family *family)
 {
        if (!WARN_ON(family->parallel_ops))
                lockdep_assert_held(&genl_mutex);
@@ -1156,8 +1096,9 @@ static int genlmsg_mcast(struct sk_buff *skb, u32 portid, unsigned long group,
        return err;
 }
 
-int genlmsg_multicast_allns(struct genl_family *family, struct sk_buff *skb,
-                           u32 portid, unsigned int group, gfp_t flags)
+int genlmsg_multicast_allns(const struct genl_family *family,
+                           struct sk_buff *skb, u32 portid,
+                           unsigned int group, gfp_t flags)
 {
        if (WARN_ON_ONCE(group >= family->n_mcgrps))
                return -EINVAL;
@@ -1166,7 +1107,7 @@ int genlmsg_multicast_allns(struct genl_family *family, struct sk_buff *skb,
 }
 EXPORT_SYMBOL(genlmsg_multicast_allns);
 
-void genl_notify(struct genl_family *family, struct sk_buff *skb,
+void genl_notify(const struct genl_family *family, struct sk_buff *skb,
                 struct genl_info *info, u32 group, gfp_t flags)
 {
        struct net *net = genl_info_net(info);