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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, David Howells <dhowells@redhat.com>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.4 23/65] rxrpc: Fix afs large storage transmission performance drop
Date:   Tue,  7 Jul 2020 17:17:02 +0200
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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