The batadv_tt_orig_list_entry structure didn't have any refcounting mechanism so far. This patch introduces it and makes the structure being usable in much more complex context.
Signed-off-by: Antonio Quartulli ordex@autistici.org --- net/batman-adv/translation-table.c | 77 +++++++++++++++++++++++++----------- net/batman-adv/types.h | 1 + 2 files changed, 54 insertions(+), 24 deletions(-)
diff --git a/net/batman-adv/translation-table.c b/net/batman-adv/translation-table.c index 99dd8f7..eb8490e 100644 --- a/net/batman-adv/translation-table.c +++ b/net/batman-adv/translation-table.c @@ -152,6 +152,8 @@ static void batadv_tt_orig_list_entry_free_rcu(struct rcu_head *rcu) static void batadv_tt_orig_list_entry_free_ref(struct batadv_tt_orig_list_entry *orig_entry) { + if (!atomic_dec_and_test(&orig_entry->refcount)) + return; /* to avoid race conditions, immediately decrease the tt counter */ atomic_dec(&orig_entry->orig_node->tt_size); call_rcu(&orig_entry->rcu, batadv_tt_orig_list_entry_free_rcu); @@ -625,50 +627,82 @@ static void batadv_tt_changes_list_free(struct batadv_priv *bat_priv) spin_unlock_bh(&bat_priv->tt_changes_list_lock); }
+/* retrieves the orig_tt_list_entry belonging to orig_node from the + * batadv_tt_global_entry list + * + * returns it with an increased refcounter, NULL if not found + */ +static struct batadv_tt_orig_list_entry * +batadv_tt_global_orig_entry_find(const struct batadv_tt_global_entry *entry, + const struct batadv_orig_node *orig_node) +{ + struct batadv_tt_orig_list_entry *tmp_orig_entry, *orig_entry = NULL; + const struct hlist_head *head; + struct hlist_node *node; + + rcu_read_lock(); + head = &entry->orig_list; + hlist_for_each_entry_rcu(tmp_orig_entry, node, head, list) { + if (tmp_orig_entry->orig_node != orig_node) + continue; + if (!atomic_inc_not_zero(&tmp_orig_entry->refcount)) + continue; + + orig_entry = tmp_orig_entry; + break; + } + rcu_read_unlock(); + + return orig_entry; +} + /* find out if an orig_node is already in the list of a tt_global_entry. - * returns 1 if found, 0 otherwise + * returns true if found, false otherwise */ static bool batadv_tt_global_entry_has_orig(const struct batadv_tt_global_entry *entry, const struct batadv_orig_node *orig_node) { - struct batadv_tt_orig_list_entry *tmp_orig_entry; - const struct hlist_head *head; - struct hlist_node *node; + struct batadv_tt_orig_list_entry *orig_entry; bool found = false;
- rcu_read_lock(); - head = &entry->orig_list; - hlist_for_each_entry_rcu(tmp_orig_entry, node, head, list) { - if (tmp_orig_entry->orig_node == orig_node) { - found = true; - break; - } + orig_entry = batadv_tt_global_orig_entry_find(entry, orig_node); + if (orig_entry) { + found = true; + batadv_tt_orig_list_entry_free_ref(orig_entry); } - rcu_read_unlock(); + return found; }
static void -batadv_tt_global_add_orig_entry(struct batadv_tt_global_entry *tt_global_entry, +batadv_tt_global_orig_entry_add(struct batadv_tt_global_entry *tt_global, struct batadv_orig_node *orig_node, int ttvn) { struct batadv_tt_orig_list_entry *orig_entry;
+ orig_entry = batadv_tt_global_orig_entry_find(tt_global, orig_node); + if (orig_entry) + goto out; + orig_entry = kzalloc(sizeof(*orig_entry), GFP_ATOMIC); if (!orig_entry) - return; + goto out;
INIT_HLIST_NODE(&orig_entry->list); atomic_inc(&orig_node->refcount); atomic_inc(&orig_node->tt_size); orig_entry->orig_node = orig_node; orig_entry->ttvn = ttvn; + atomic_set(&orig_entry->refcount, 2);
- spin_lock_bh(&tt_global_entry->list_lock); + spin_lock_bh(&tt_global->list_lock); hlist_add_head_rcu(&orig_entry->list, - &tt_global_entry->orig_list); - spin_unlock_bh(&tt_global_entry->list_lock); + &tt_global->orig_list); + spin_unlock_bh(&tt_global->list_lock); +out: + if (orig_entry) + batadv_tt_orig_list_entry_free_ref(orig_entry); }
/* caller must hold orig_node refcount */ @@ -709,9 +743,6 @@ int batadv_tt_global_add(struct batadv_priv *bat_priv, batadv_tt_global_entry_free_ref(tt_global_entry); goto out_remove; } - - batadv_tt_global_add_orig_entry(tt_global_entry, orig_node, - ttvn); } else { /* there is already a global entry, use this one. */
@@ -728,11 +759,9 @@ int batadv_tt_global_add(struct batadv_priv *bat_priv, tt_global_entry->roam_at = 0; }
- if (!batadv_tt_global_entry_has_orig(tt_global_entry, - orig_node)) - batadv_tt_global_add_orig_entry(tt_global_entry, - orig_node, ttvn); } + /* add the new orig_entry (if needed) */ + batadv_tt_global_orig_entry_add(tt_global_entry, orig_node, ttvn);
batadv_dbg(BATADV_DBG_TT, bat_priv, "Creating new global tt entry: %pM (via %pM)\n", diff --git a/net/batman-adv/types.h b/net/batman-adv/types.h index 7812b6e..664ef81 100644 --- a/net/batman-adv/types.h +++ b/net/batman-adv/types.h @@ -282,6 +282,7 @@ struct batadv_tt_global_entry { struct batadv_tt_orig_list_entry { struct batadv_orig_node *orig_node; uint8_t ttvn; + atomic_t refcount; struct rcu_head rcu; struct hlist_node list; };