[PATCH net-next 1/4] net: shaper: drop redundant xa_lock() bracketing

[Jakub Kicinski <kuba@kernel.org>]

The shaper insertion and update code takes xa_lock() explicitly.
Paolo explained that the locking was purely to avoid re-taking
the lock in loops. But it may be mis-read as if it was expecting
readers to be fenced off by xa_lock. Readers of XArray are purely
under RCU. Remove explicit taking of xa_lock().

All writers to hierarchy->shapers are serialized by the netdev
instance lock (or run after netdev is made inaccessible to readers).

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---
 net/shaper/shaper.c | 10 ++--------
 1 file changed, 2 insertions(+), 8 deletions(-)

diff --git a/net/shaper/shaper.c b/net/shaper/shaper.c
index dea9270f3e57..a5b42b697a93 100644
--- a/net/shaper/shaper.c
+++ b/net/shaper/shaper.c
@@ -429,7 +429,6 @@ static void net_shaper_commit(struct net_shaper_binding *binding,
 	int index;
 	int i;
 
-	xa_lock(&hierarchy->shapers);
 	for (i = 0; i < nr_shapers; ++i) {
 		index = net_shaper_handle_to_index(&shapers[i].handle);
 
@@ -442,7 +441,6 @@ static void net_shaper_commit(struct net_shaper_binding *binding,
 		/* ... publish to lockless readers. */
 		smp_store_release(&cur->valid, true);
 	}
-	xa_unlock(&hierarchy->shapers);
 }
 
 /* Rollback all the tentative inserts from the hierarchy. */
@@ -455,14 +453,12 @@ static void net_shaper_rollback(struct net_shaper_binding *binding)
 	if (!hierarchy)
 		return;
 
-	xa_lock(&hierarchy->shapers);
 	xa_for_each(&hierarchy->shapers, index, cur) {
 		if (cur->valid)
 			continue;
-		__xa_erase(&hierarchy->shapers, index);
+		xa_erase(&hierarchy->shapers, index);
 		kfree_rcu(cur, rcu);
 	}
-	xa_unlock(&hierarchy->shapers);
 }
 
 static int net_shaper_parse_handle(const struct nlattr *attr,
@@ -1472,12 +1468,10 @@ static void net_shaper_flush(struct net_shaper_binding *binding)
 	if (!hierarchy)
 		return;
 
-	xa_lock(&hierarchy->shapers);
 	xa_for_each(&hierarchy->shapers, index, cur) {
-		__xa_erase(&hierarchy->shapers, index);
+		xa_erase(&hierarchy->shapers, index);
 		kfree(cur);
 	}
-	xa_unlock(&hierarchy->shapers);
 
 	kfree(hierarchy);
 }
-- 
2.54.0