rxrpc: Reduce the use of RCU in packet input

Shrink the region of rxrpc_input_packet() that is covered by the RCU read
lock so that it only covers the connection and call lookup.  This means
that the bits now outside of that can call sleepable functions such as
kmalloc and sendmsg.

Also take a ref on the conn or call we're going to use before we drop the
RCU read lock.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org

1 files changed, 3 insertions, 10 deletions

diff --git a/net/rxrpc/call_accept.c b/net/rxrpc/call_accept.c
index 5f978b0b2404..beb8efa2e7a9 100644
--- a/net/rxrpc/call_accept.c
+++ b/net/rxrpc/call_accept.c
@@ -336,13 +336,13 @@ static struct rxrpc_call *rxrpc_alloc_incoming_call(struct rxrpc_sock *rx,
  * If this is for a kernel service, when we allocate the call, it will have
  * three refs on it: (1) the kernel service, (2) the user_call_ID tree, (3) the
  * retainer ref obtained from the backlog buffer.  Prealloc calls for userspace
- * services only have the ref from the backlog buffer.  We want to pass this
- * ref to non-BH context to dispose of.
+ * services only have the ref from the backlog buffer.  We pass this ref to the
+ * caller.
  *
  * If we want to report an error, we mark the skb with the packet type and
  * abort code and return NULL.
  *
- * The call is returned with the user access mutex held.
+ * The call is returned with the user access mutex held and a ref on it.
  */
 struct rxrpc_call *rxrpc_new_incoming_call(struct rxrpc_local *local,
 					   struct rxrpc_sock *rx,
@@ -426,13 +426,6 @@ struct rxrpc_call *rxrpc_new_incoming_call(struct rxrpc_local *local,
 
 	rxrpc_send_ping(call, skb);
 
-	/* We have to discard the prealloc queue's ref here and rely on a
-	 * combination of the RCU read lock and refs held either by the socket
-	 * (recvmsg queue, to-be-accepted queue or user ID tree) or the kernel
-	 * service to prevent the call from being deallocated too early.
-	 */
-	rxrpc_put_call(call, rxrpc_call_put_discard_prealloc);
-
 	if (hlist_unhashed(&call->error_link)) {
 		spin_lock(&call->peer->lock);
 		hlist_add_head(&call->error_link, &call->peer->error_targets);