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Subject[PATCH AUTOSEL 4.18 043/100] rxrpc: Fix error distribution
Date
From: David Howells <dhowells@redhat.com>

[ Upstream commit f334430316e7fd37c4821ebec627e27714bb5d76 ]

Fix error distribution by immediately delivering the errors to all the
affected calls rather than deferring them to a worker thread. The problem
with the latter is that retries and things can happen in the meantime when we
want to stop that sooner.

To this end:

(1) Stop the error distributor from removing calls from the error_targets
list so that peer->lock isn't needed to synchronise against other adds
and removals.

(2) Require the peer's error_targets list to be accessed with RCU, thereby
avoiding the need to take peer->lock over distribution.

(3) Don't attempt to affect a call's state if it is already marked complete.

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
include/trace/events/rxrpc.h | 4 +---
net/rxrpc/ar-internal.h | 5 ----
net/rxrpc/call_object.c | 2 +-
net/rxrpc/conn_client.c | 4 ++--
net/rxrpc/conn_object.c | 2 +-
net/rxrpc/peer_event.c | 46 +++++++++---------------------------
net/rxrpc/peer_object.c | 17 -------------
7 files changed, 16 insertions(+), 64 deletions(-)

diff --git a/include/trace/events/rxrpc.h b/include/trace/events/rxrpc.h
index 4fff00e9da8a..0a774b64fc29 100644
--- a/include/trace/events/rxrpc.h
+++ b/include/trace/events/rxrpc.h
@@ -56,7 +56,6 @@ enum rxrpc_peer_trace {
rxrpc_peer_new,
rxrpc_peer_processing,
rxrpc_peer_put,
- rxrpc_peer_queued_error,
};

enum rxrpc_conn_trace {
@@ -257,8 +256,7 @@ enum rxrpc_tx_fail_trace {
EM(rxrpc_peer_got, "GOT") \
EM(rxrpc_peer_new, "NEW") \
EM(rxrpc_peer_processing, "PRO") \
- EM(rxrpc_peer_put, "PUT") \
- E_(rxrpc_peer_queued_error, "QER")
+ E_(rxrpc_peer_put, "PUT")

#define rxrpc_conn_traces \
EM(rxrpc_conn_got, "GOT") \
diff --git a/net/rxrpc/ar-internal.h b/net/rxrpc/ar-internal.h
index 5069193d2cc1..4718d08c0af1 100644
--- a/net/rxrpc/ar-internal.h
+++ b/net/rxrpc/ar-internal.h
@@ -293,7 +293,6 @@ struct rxrpc_peer {
struct hlist_node hash_link;
struct rxrpc_local *local;
struct hlist_head error_targets; /* targets for net error distribution */
- struct work_struct error_distributor;
struct rb_root service_conns; /* Service connections */
struct list_head keepalive_link; /* Link in net->peer_keepalive[] */
time64_t last_tx_at; /* Last time packet sent here */
@@ -304,8 +303,6 @@ struct rxrpc_peer {
unsigned int maxdata; /* data size (MTU - hdrsize) */
unsigned short hdrsize; /* header size (IP + UDP + RxRPC) */
int debug_id; /* debug ID for printks */
- int error_report; /* Net (+0) or local (+1000000) to distribute */
-#define RXRPC_LOCAL_ERROR_OFFSET 1000000
struct sockaddr_rxrpc srx; /* remote address */

/* calculated RTT cache */
@@ -1039,7 +1036,6 @@ void rxrpc_send_keepalive(struct rxrpc_peer *);
* peer_event.c
*/
void rxrpc_error_report(struct sock *);
-void rxrpc_peer_error_distributor(struct work_struct *);
void rxrpc_peer_add_rtt(struct rxrpc_call *, enum rxrpc_rtt_rx_trace,
rxrpc_serial_t, rxrpc_serial_t, ktime_t, ktime_t);
void rxrpc_peer_keepalive_worker(struct work_struct *);
@@ -1058,7 +1054,6 @@ void rxrpc_destroy_all_peers(struct rxrpc_net *);
struct rxrpc_peer *rxrpc_get_peer(struct rxrpc_peer *);
struct rxrpc_peer *rxrpc_get_peer_maybe(struct rxrpc_peer *);
void rxrpc_put_peer(struct rxrpc_peer *);
-void __rxrpc_queue_peer_error(struct rxrpc_peer *);

/*
* proc.c
diff --git a/net/rxrpc/call_object.c b/net/rxrpc/call_object.c
index f6734d8cb01a..ed69257203c2 100644
--- a/net/rxrpc/call_object.c
+++ b/net/rxrpc/call_object.c
@@ -400,7 +400,7 @@ void rxrpc_incoming_call(struct rxrpc_sock *rx,
rcu_assign_pointer(conn->channels[chan].call, call);

spin_lock(&conn->params.peer->lock);
- hlist_add_head(&call->error_link, &conn->params.peer->error_targets);
+ hlist_add_head_rcu(&call->error_link, &conn->params.peer->error_targets);
spin_unlock(&conn->params.peer->lock);

_net("CALL incoming %d on CONN %d", call->debug_id, call->conn->debug_id);
diff --git a/net/rxrpc/conn_client.c b/net/rxrpc/conn_client.c
index 5736f643c516..0be19132202b 100644
--- a/net/rxrpc/conn_client.c
+++ b/net/rxrpc/conn_client.c
@@ -709,8 +709,8 @@ int rxrpc_connect_call(struct rxrpc_call *call,
}

spin_lock_bh(&call->conn->params.peer->lock);
- hlist_add_head(&call->error_link,
- &call->conn->params.peer->error_targets);
+ hlist_add_head_rcu(&call->error_link,
+ &call->conn->params.peer->error_targets);
spin_unlock_bh(&call->conn->params.peer->lock);

out:
diff --git a/net/rxrpc/conn_object.c b/net/rxrpc/conn_object.c
index c37bf8e282b9..e0d6d0fb7426 100644
--- a/net/rxrpc/conn_object.c
+++ b/net/rxrpc/conn_object.c
@@ -214,7 +214,7 @@ void rxrpc_disconnect_call(struct rxrpc_call *call)
call->peer->cong_cwnd = call->cong_cwnd;

spin_lock_bh(&conn->params.peer->lock);
- hlist_del_init(&call->error_link);
+ hlist_del_rcu(&call->error_link);
spin_unlock_bh(&conn->params.peer->lock);

if (rxrpc_is_client_call(call))
diff --git a/net/rxrpc/peer_event.c b/net/rxrpc/peer_event.c
index 4f9da2f51c69..f3e6fc670da2 100644
--- a/net/rxrpc/peer_event.c
+++ b/net/rxrpc/peer_event.c
@@ -23,6 +23,8 @@
#include "ar-internal.h"

static void rxrpc_store_error(struct rxrpc_peer *, struct sock_exterr_skb *);
+static void rxrpc_distribute_error(struct rxrpc_peer *, int,
+ enum rxrpc_call_completion);

/*
* Find the peer associated with an ICMP packet.
@@ -194,8 +196,6 @@ void rxrpc_error_report(struct sock *sk)
rcu_read_unlock();
rxrpc_free_skb(skb, rxrpc_skb_rx_freed);

- /* The ref we obtained is passed off to the work item */
- __rxrpc_queue_peer_error(peer);
_leave("");
}

@@ -205,6 +205,7 @@ void rxrpc_error_report(struct sock *sk)
static void rxrpc_store_error(struct rxrpc_peer *peer,
struct sock_exterr_skb *serr)
{
+ enum rxrpc_call_completion compl = RXRPC_CALL_NETWORK_ERROR;
struct sock_extended_err *ee;
int err;

@@ -255,7 +256,7 @@ static void rxrpc_store_error(struct rxrpc_peer *peer,
case SO_EE_ORIGIN_NONE:
case SO_EE_ORIGIN_LOCAL:
_proto("Rx Received local error { error=%d }", err);
- err += RXRPC_LOCAL_ERROR_OFFSET;
+ compl = RXRPC_CALL_LOCAL_ERROR;
break;

case SO_EE_ORIGIN_ICMP6:
@@ -264,48 +265,23 @@ static void rxrpc_store_error(struct rxrpc_peer *peer,
break;
}

- peer->error_report = err;
+ rxrpc_distribute_error(peer, err, compl);
}

/*
- * Distribute an error that occurred on a peer
+ * Distribute an error that occurred on a peer.
*/
-void rxrpc_peer_error_distributor(struct work_struct *work)
+static void rxrpc_distribute_error(struct rxrpc_peer *peer, int error,
+ enum rxrpc_call_completion compl)
{
- struct rxrpc_peer *peer =
- container_of(work, struct rxrpc_peer, error_distributor);
struct rxrpc_call *call;
- enum rxrpc_call_completion compl;
- int error;
-
- _enter("");
-
- error = READ_ONCE(peer->error_report);
- if (error < RXRPC_LOCAL_ERROR_OFFSET) {
- compl = RXRPC_CALL_NETWORK_ERROR;
- } else {
- compl = RXRPC_CALL_LOCAL_ERROR;
- error -= RXRPC_LOCAL_ERROR_OFFSET;
- }

- _debug("ISSUE ERROR %s %d", rxrpc_call_completions[compl], error);
-
- spin_lock_bh(&peer->lock);
-
- while (!hlist_empty(&peer->error_targets)) {
- call = hlist_entry(peer->error_targets.first,
- struct rxrpc_call, error_link);
- hlist_del_init(&call->error_link);
+ hlist_for_each_entry_rcu(call, &peer->error_targets, error_link) {
rxrpc_see_call(call);
-
- if (rxrpc_set_call_completion(call, compl, 0, -error))
+ if (call->state < RXRPC_CALL_COMPLETE &&
+ rxrpc_set_call_completion(call, compl, 0, -error))
rxrpc_notify_socket(call);
}
-
- spin_unlock_bh(&peer->lock);
-
- rxrpc_put_peer(peer);
- _leave("");
}

/*
diff --git a/net/rxrpc/peer_object.c b/net/rxrpc/peer_object.c
index 24ec7cdcf332..ef4c2e8a35cc 100644
--- a/net/rxrpc/peer_object.c
+++ b/net/rxrpc/peer_object.c
@@ -222,8 +222,6 @@ struct rxrpc_peer *rxrpc_alloc_peer(struct rxrpc_local *local, gfp_t gfp)
atomic_set(&peer->usage, 1);
peer->local = local;
INIT_HLIST_HEAD(&peer->error_targets);
- INIT_WORK(&peer->error_distributor,
- &rxrpc_peer_error_distributor);
peer->service_conns = RB_ROOT;
seqlock_init(&peer->service_conn_lock);
spin_lock_init(&peer->lock);
@@ -415,21 +413,6 @@ struct rxrpc_peer *rxrpc_get_peer_maybe(struct rxrpc_peer *peer)
return peer;
}

-/*
- * Queue a peer record. This passes the caller's ref to the workqueue.
- */
-void __rxrpc_queue_peer_error(struct rxrpc_peer *peer)
-{
- const void *here = __builtin_return_address(0);
- int n;
-
- n = atomic_read(&peer->usage);
- if (rxrpc_queue_work(&peer->error_distributor))
- trace_rxrpc_peer(peer, rxrpc_peer_queued_error, n, here);
- else
- rxrpc_put_peer(peer);
-}
-
/*
* Discard a peer record.
*/
--
2.17.1
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