[ Upstream commit a95d25dd7b94a5ba18246da09b4218f132fed60e ]
The call state may be changed at any time by the data-ready routine in
response to received packets, so if the call state is to be read and acted
upon several times in a function, READ_ONCE() must be used unless the call
state lock is held.
As it happens, we used READ_ONCE() to read the state a few lines above the
unmarked read in rxrpc_input_data(), so use that value rather than
re-reading it.
Fixes: a158bdd3247b ("rxrpc: Fix call timeouts")
Signed-off-by: Baptiste Lepers <baptiste.lepers@gmail.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Link: https://lore.kernel.org/r/161046715522.2450566.488819910256264150.stgit@warthog.procyon.org.uk
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[ Upstream commit 68528d937dcd675e79973061c1a314db598162d1 ]
Keep the ACK serial number in a variable in rxrpc_input_ack() as it's used
frequently.
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
[ Upstream commit a2ad7c21ad8cf1ce4ad65e13df1c2a1c29b38ac5 ]
The handling of the receive window size (rwind) from a received ACK packet
is not correct. The rxrpc_input_ackinfo() function currently checks the
current Tx window size against the rwind from the ACK to see if it has
changed, but then limits the rwind size before storing it in the tx_winsize
member and, if it increased, wake up the transmitting process. This means
that if rwind > RXRPC_RXTX_BUFF_SIZE - 1, this path will always be
followed.
Fix this by limiting rwind before we compare it to tx_winsize.
The effect of this can be seen by enabling the rxrpc_rx_rwind_change
tracepoint.
Fixes: 702f2ac87a9a ("rxrpc: Wake up the transmitter if Rx window size increases on the peer")
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
[ Upstream commit 441fdee1eaf050ef0040bde0d7af075c1c6a6d8b ]
The Rx protocol has a "previousPacket" field in it that is not handled in
the same way by all protocol implementations. Sometimes it contains the
serial number of the last DATA packet received, sometimes the sequence
number of the last DATA packet received and sometimes the highest sequence
number so far received.
AF_RXRPC is using this to weed out ACKs that are out of date (it's possible
for ACK packets to get reordered on the wire), but this does not work with
OpenAFS which will just stick the sequence number of the last packet seen
into previousPacket.
The issue being seen is that big AFS FS.StoreData RPC (eg. of ~256MiB) are
timing out when partly sent. A trace was captured, with an additional
tracepoint to show ACKs being discarded in rxrpc_input_ack(). Here's an
excerpt showing the problem.
52873.203230: rxrpc_tx_data: c=000004ae DATA ed1a3584:00000002 0002449c q=00024499 fl=09
A DATA packet with sequence number 00024499 has been transmitted (the "q="
field).
...
52873.243296: rxrpc_rx_ack: c=000004ae 00012a2b DLY r=00024499 f=00024497 p=00024496 n=0
52873.243376: rxrpc_rx_ack: c=000004ae 00012a2c IDL r=0002449b f=00024499 p=00024498 n=0
52873.243383: rxrpc_rx_ack: c=000004ae 00012a2d OOS r=0002449d f=00024499 p=0002449a n=2
The Out-Of-Sequence ACK indicates that the server didn't see DATA sequence
number 00024499, but did see seq 0002449a (previousPacket, shown as "p=",
skipped the number, but firstPacket, "f=", which shows the bottom of the
window is set at that point).
52873.252663: rxrpc_retransmit: c=000004ae q=24499 a=02 xp=14581537
52873.252664: rxrpc_tx_data: c=000004ae DATA ed1a3584:00000002 000244bc q=00024499 fl=0b *RETRANS*
The packet has been retransmitted. Retransmission recurs until the peer
says it got the packet.
52873.271013: rxrpc_rx_ack: c=000004ae 00012a31 OOS r=000244a1 f=00024499 p=0002449e n=6
More OOS ACKs indicate that the other packets that are already in the
transmission pipeline are being received. The specific-ACK list is up to 6
ACKs and NAKs.
...
52873.284792: rxrpc_rx_ack: c=000004ae 00012a49 OOS r=000244b9 f=00024499 p=000244b6 n=30
52873.284802: rxrpc_retransmit: c=000004ae q=24499 a=0a xp=63505500
52873.284804: rxrpc_tx_data: c=000004ae DATA ed1a3584:00000002 000244c2 q=00024499 fl=0b *RETRANS*
52873.287468: rxrpc_rx_ack: c=000004ae 00012a4a OOS r=000244ba f=00024499 p=000244b7 n=31
52873.287478: rxrpc_rx_ack: c=000004ae 00012a4b OOS r=000244bb f=00024499 p=000244b8 n=32
At this point, the server's receive window is full (n=32) with presumably 1
NAK'd packet and 31 ACK'd packets. We can't transmit any more packets.
52873.287488: rxrpc_retransmit: c=000004ae q=24499 a=0a xp=61327980
52873.287489: rxrpc_tx_data: c=000004ae DATA ed1a3584:00000002 000244c3 q=00024499 fl=0b *RETRANS*
52873.293850: rxrpc_rx_ack: c=000004ae 00012a4c DLY r=000244bc f=000244a0 p=00024499 n=25
And now we've received an ACK indicating that a DATA retransmission was
received. 7 packets have been processed (the occupied part of the window
moved, as indicated by f= and n=).
52873.293853: rxrpc_rx_discard_ack: c=000004ae r=00012a4c 000244a0<00024499 00024499<000244b8
However, the DLY ACK gets discarded because its previousPacket has gone
backwards (from p=000244b8, in the ACK at 52873.287478 to p=00024499 in the
ACK at 52873.293850).
We then end up in a continuous cycle of retransmit/discard. kafs fails to
update its window because it's discarding the ACKs and can't transmit an
extra packet that would clear the issue because the window is full.
OpenAFS doesn't change the previousPacket value in the ACKs because no new
DATA packets are received with a different previousPacket number.
Fix this by altering the discard check to only discard an ACK based on
previousPacket if there was no advance in the firstPacket. This allows us
to transmit a new packet which will cause previousPacket to advance in the
next ACK.
The check, however, needs to allow for the possibility that previousPacket
may actually have had the serial number placed in it instead - in which
case it will go outside the window and we should ignore it.
Fixes: 1a2391c30c0b ("rxrpc: Fix detection of out of order acks")
Reported-by: Dave Botsch <botsch@cnf.cornell.edu>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
[ Upstream commit d1f129470e6cb79b8b97fecd12689f6eb49e27fe ]
Add a tracepoint to track received ACKs that are discarded due to being
outside of the Tx window.
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
commit c410bf01933e5e09d142c66c3df9ad470a7eec13 upstream.
rxrpc currently uses a fixed 4s retransmission timeout until the RTT is
sufficiently sampled. This can cause problems with some fileservers with
calls to the cache manager in the afs filesystem being dropped from the
fileserver because a packet goes missing and the retransmission timeout is
greater than the call expiry timeout.
Fix this by:
(1) Copying the RTT/RTO calculation code from Linux's TCP implementation
and altering it to fit rxrpc.
(2) Altering the various users of the RTT to make use of the new SRTT
value.
(3) Replacing the use of rxrpc_resend_timeout to use the calculated RTO
value instead (which is needed in jiffies), along with a backoff.
Notes:
(1) rxrpc provides RTT samples by matching the serial numbers on outgoing
DATA packets that have the RXRPC_REQUEST_ACK set and PING ACK packets
against the reference serial number in incoming REQUESTED ACK and
PING-RESPONSE ACK packets.
(2) Each packet that is transmitted on an rxrpc connection gets a new
per-connection serial number, even for retransmissions, so an ACK can
be cross-referenced to a specific trigger packet. This allows RTT
information to be drawn from retransmitted DATA packets also.
(3) rxrpc maintains the RTT/RTO state on the rxrpc_peer record rather than
on an rxrpc_call because many RPC calls won't live long enough to
generate more than one sample.
(4) The calculated SRTT value is in units of 8ths of a microsecond rather
than nanoseconds.
The (S)RTT and RTO values are displayed in /proc/net/rxrpc/peers.
Fixes: 17926a79320a ([AF_RXRPC]: Provide secure RxRPC sockets for use by userspace and kernel both"")
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Baptiste Lepers