[PATCH 5.7 049/112] rxrpc: Fix afs large storage transmission performance drop

Greg Kroah-Hartman
2020-07-07T15:24:32Z

From: David Howells <dhowells@redhat.com>

[ Upstream commit 02c28dffb13abbaaedece1e4a6493b48ad3f913a ]

Commit 2ad6691d988c, which moved the modification of the status annotation
for a packet in the Tx buffer prior to the retransmission moved the state
clearance, but managed to lose the bit that set it to UNACK.

Consequently, if a retransmission occurs, the packet is accidentally
changed to the ACK state (ie. 0) by masking it off, which means that the
packet isn't counted towards the tally of newly-ACK'd packets if it gets
hard-ACK'd. This then prevents the congestion control algorithm from
recovering properly.

Fix by reinstating the change of state to UNACK.

Spotted by the generic/460 xfstest.

Fixes: 2ad6691d988c ("rxrpc: Fix race between incoming ACK parser and retransmitter")
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/rxrpc/call_event.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/rxrpc/call_event.c b/net/rxrpc/call_event.c
index 985fb89202d0c..9ff85ee8337cd 100644
--- a/net/rxrpc/call_event.c
+++ b/net/rxrpc/call_event.c
@@ -253,7 +253,7 @@ static void rxrpc_resend(struct rxrpc_call *call, unsigned long now_j)
* confuse things
*/
annotation &= ~RXRPC_TX_ANNO_MASK;
- annotation |= RXRPC_TX_ANNO_RESENT;
+ annotation |= RXRPC_TX_ANNO_UNACK | RXRPC_TX_ANNO_RESENT;
call->rxtx_annotations[ix] = annotation;

skb = call->rxtx_buffer[ix];
--
2.25.1