The following commit has been merged in the batadv/net-next branch: commit 8587e0e3f562b09bbfe0df1b0c506066095043e4 Author: Remi Pommarel repk@triplefau.lt Date: Fri Nov 22 16:52:51 2024 +0100

batman-adv: Remove atomic usage for tt.local_changes

The tt.local_changes atomic is either written with tt.changes_list_lock or close to it (see batadv_tt_local_event()). Thus the performance gain using an atomic was limited (or because of atomic_read() impact even negative). Using atomic also comes with the need to be wary of potential negative tt.local_changes value.

Simplify the tt.local_changes usage by removing the atomic property and modifying it only with tt.changes_list_lock held.

Signed-off-by: Remi Pommarel repk@triplefau.lt Signed-off-by: Sven Eckelmann sven@narfation.org Signed-off-by: Simon Wunderlich sw@simonwunderlich.de

diff --git a/net/batman-adv/soft-interface.c b/net/batman-adv/soft-interface.c index 2758aba47a2f2..5666c268cead2 100644 --- a/net/batman-adv/soft-interface.c +++ b/net/batman-adv/soft-interface.c @@ -783,13 +783,13 @@ static int batadv_softif_init_late(struct net_device *dev) atomic_set(&bat_priv->mesh_state, BATADV_MESH_INACTIVE); atomic_set(&bat_priv->bcast_seqno, 1); atomic_set(&bat_priv->tt.vn, 0); - atomic_set(&bat_priv->tt.local_changes, 0); atomic_set(&bat_priv->tt.ogm_append_cnt, 0); #ifdef CONFIG_BATMAN_ADV_BLA atomic_set(&bat_priv->bla.num_requests, 0); #endif atomic_set(&bat_priv->tp_num, 0);

+ WRITE_ONCE(bat_priv->tt.local_changes, 0); bat_priv->tt.last_changeset = NULL; bat_priv->tt.last_changeset_len = 0; bat_priv->isolation_mark = 0; diff --git a/net/batman-adv/translation-table.c b/net/batman-adv/translation-table.c index b44c382226a11..6e0345b91ece2 100644 --- a/net/batman-adv/translation-table.c +++ b/net/batman-adv/translation-table.c @@ -423,8 +423,8 @@ static void batadv_tt_local_event(struct batadv_priv *bat_priv, struct batadv_tt_change_node *tt_change_node, *entry, *safe; struct batadv_tt_common_entry *common = &tt_local_entry->common; u8 flags = common->flags | event_flags; - bool event_removed = false; bool del_op_requested, del_op_entry; + size_t changes;

tt_change_node = kmem_cache_alloc(batadv_tt_change_cache, GFP_ATOMIC); if (!tt_change_node) @@ -440,6 +440,7 @@ static void batadv_tt_local_event(struct batadv_priv *bat_priv,

/* check for ADD+DEL or DEL+ADD events */ spin_lock_bh(&bat_priv->tt.changes_list_lock); + changes = READ_ONCE(bat_priv->tt.local_changes); list_for_each_entry_safe(entry, safe, &bat_priv->tt.changes_list, list) { if (!batadv_compare_eth(entry->change.addr, common->addr)) @@ -468,21 +469,18 @@ static void batadv_tt_local_event(struct batadv_priv *bat_priv, del: list_del(&entry->list); kmem_cache_free(batadv_tt_change_cache, entry); + changes--; kmem_cache_free(batadv_tt_change_cache, tt_change_node); - event_removed = true; - goto unlock; + goto update_changes; }

/* track the change in the OGMinterval list */ list_add_tail(&tt_change_node->list, &bat_priv->tt.changes_list); + changes++;

-unlock: +update_changes: + WRITE_ONCE(bat_priv->tt.local_changes, changes); spin_unlock_bh(&bat_priv->tt.changes_list_lock); - - if (event_removed) - atomic_dec(&bat_priv->tt.local_changes); - else - atomic_inc(&bat_priv->tt.local_changes); }

/** @@ -950,7 +948,7 @@ static void batadv_tt_tvlv_container_update(struct batadv_priv *bat_priv) int tt_diff_entries_count = 0; u16 tvlv_len;

- tt_diff_entries_num = atomic_read(&bat_priv->tt.local_changes); + tt_diff_entries_num = READ_ONCE(bat_priv->tt.local_changes); tt_diff_len = batadv_tt_len(tt_diff_entries_num);

/* if we have too many changes for one packet don't send any @@ -970,7 +968,7 @@ static void batadv_tt_tvlv_container_update(struct batadv_priv *bat_priv) goto container_register;

spin_lock_bh(&bat_priv->tt.changes_list_lock); - atomic_set(&bat_priv->tt.local_changes, 0); + WRITE_ONCE(bat_priv->tt.local_changes, 0);

list_for_each_entry_safe(entry, safe, &bat_priv->tt.changes_list, list) { @@ -1380,7 +1378,7 @@ static void batadv_tt_changes_list_free(struct batadv_priv *bat_priv) kmem_cache_free(batadv_tt_change_cache, entry); }

- atomic_set(&bat_priv->tt.local_changes, 0); + WRITE_ONCE(bat_priv->tt.local_changes, 0); spin_unlock_bh(&bat_priv->tt.changes_list_lock); }

@@ -3634,7 +3632,7 @@ static void batadv_tt_local_commit_changes_nolock(struct batadv_priv *bat_priv) { lockdep_assert_held(&bat_priv->tt.commit_lock);

- if (atomic_read(&bat_priv->tt.local_changes) < 1) { + if (READ_ONCE(bat_priv->tt.local_changes) == 0) { if (!batadv_atomic_dec_not_zero(&bat_priv->tt.ogm_append_cnt)) batadv_tt_tvlv_container_update(bat_priv); return; diff --git a/net/batman-adv/types.h b/net/batman-adv/types.h index 04f6398b3a40e..f491bff8c51b8 100644 --- a/net/batman-adv/types.h +++ b/net/batman-adv/types.h @@ -1022,7 +1022,7 @@ struct batadv_priv_tt { atomic_t ogm_append_cnt;

/** @local_changes: changes registered in an originator interval */ - atomic_t local_changes; + size_t local_changes;

/** * @changes_list: tracks tt local changes within an originator interval @@ -1044,7 +1044,7 @@ struct batadv_priv_tt { */ struct list_head roam_list;

- /** @changes_list_lock: lock protecting changes_list */ + /** @changes_list_lock: lock protecting changes_list & local_changes */ spinlock_t changes_list_lock;

/** @req_list_lock: lock protecting req_list */