linux.git/net/rxrpc/proc.c, branch v6.5

rxrpc: De-atomic call->ackr_window and call->ackr_nr_unacked

2023-01-31T16:38:26+00:00

call->ackr_window doesn't need to be atomic as ACK generation and ACK
transmission are now done in the same thread, so drop the atomic64 handling
and split it into two separate members.

Similarly, call->ackr_nr_unacked doesn't need to be atomic now either.

Signed-off-by: David Howells 
cc: Marc Dionne 
cc: linux-afs@lists.infradead.org

rxrpc: Move client call connection to the I/O thread

2023-01-06T09:43:33+00:00

Move the connection setup of client calls to the I/O thread so that a whole
load of locking and barrierage can be eliminated.  This necessitates the
app thread waiting for connection to complete before it can begin
encrypting data.

This also completes the fix for a race that exists between call connection
and call disconnection whereby the data transmission code adds the call to
the peer error distribution list after the call has been disconnected (say
by the rxrpc socket getting closed).

The fix is to complete the process of moving call connection, data
transmission and call disconnection into the I/O thread and thus forcibly
serialising them.

Note that the issue may predate the overhaul to an I/O thread model that
were included in the merge window for v6.2, but the timing is very much
changed by the change given below.

Fixes: cf37b5987508 ("rxrpc: Move DATA transmission into call processor work item")
Reported-by: syzbot+c22650d2844392afdcfd@syzkaller.appspotmail.com
Signed-off-by: David Howells 
cc: Marc Dionne 
cc: linux-afs@lists.infradead.org

rxrpc: Remove call->state_lock

2023-01-06T09:43:33+00:00

All the setters of call->state are now in the I/O thread and thus the state
lock is now unnecessary.

Signed-off-by: David Howells 
cc: Marc Dionne 
cc: linux-afs@lists.infradead.org

rxrpc: Clean up connection abort

2023-01-06T09:43:32+00:00

Clean up connection abort, using the connection state_lock to gate access
to change that state, and use an rxrpc_call_completion value to indicate
the difference between local and remote aborts as these can be pasted
directly into the call state.

Signed-off-by: David Howells 
cc: Marc Dionne 
cc: linux-afs@lists.infradead.org

rxrpc: Move the cwnd degradation after transmitting packets

2022-12-01T13:36:43+00:00

When we've gone for >1RTT without transmitting a packet, we should reduce
the ssthresh and cut the cwnd by half (as suggested in RFC2861 sec 3.1).

However, we may receive ACK packets in a batch and the first of these may
cut the cwnd, preventing further transmission, and each subsequent one cuts
the cwnd yet further, reducing it to the floor and killing performance.

Fix this by moving the cwnd reset to after doing the transmission and
resetting the base time such that we don't cut the cwnd by half again for
at least another RTT.

Signed-off-by: David Howells 
cc: Marc Dionne 
cc: linux-afs@lists.infradead.org

rxrpc: Trace/count transmission underflows and cwnd resets

2022-12-01T13:36:42+00:00

Add a tracepoint to log when a cwnd reset occurs due to lack of
transmission on a call.

Add stat counters to count transmission underflows (ie. when we have tx
window space, but sendmsg doesn't manage to keep up), cwnd resets and
transmission failures.

Signed-off-by: David Howells 
cc: Marc Dionne 
cc: linux-afs@lists.infradead.org

rxrpc: Copy client call parameters into rxrpc_call earlier

2022-12-01T13:36:41+00:00

Copy client call parameters into rxrpc_call earlier so that that can be
used to convey them to the connection code - which can then be offloaded to
the I/O thread.

Signed-off-by: David Howells 
cc: Marc Dionne 
cc: linux-afs@lists.infradead.org

rxrpc: Create a per-local endpoint receive queue and I/O thread

2022-12-01T13:36:40+00:00

Create a per-local receive queue to which, in a future patch, all incoming
packets will be directed and an I/O thread that will process those packets
and perform all transmission of packets.

Destruction of the local endpoint is also moved from the local processor
work item (which will be absorbed) to the thread.

Signed-off-by: David Howells 
cc: Marc Dionne 
cc: linux-afs@lists.infradead.org

rxrpc: Don't hold a ref for connection workqueue

2022-12-01T13:36:40+00:00

Currently, rxrpc gives the connection's work item a ref on the connection
when it queues it - and this is called from the timer expiration function.
The problem comes when queue_work() fails (ie. the work item is already
queued): the timer routine must put the ref - but this may cause the
cleanup code to run.

This has the unfortunate effect that the cleanup code may then be run in
softirq context - which means that any spinlocks it might need to touch
have to be guarded to disable softirqs (ie. they need a "_bh" suffix).

 (1) Don't give a ref to the work item.

 (2) Simplify handling of service connections by adding a separate active
     count so that the refcount isn't also used for this.

 (3) Connection destruction for both client and service connections can
     then be cleaned up by putting rxrpc_put_connection() out of line and
     making a tidy progression through the destruction code (offloaded to a
     workqueue if put from softirq or processor function context).  The RCU
     part of the cleanup then only deals with the freeing at the end.

 (4) Make rxrpc_queue_conn() return immediately if it sees the active count
     is -1 rather then queuing the connection.

 (5) Make sure that the cleanup routine waits for the work item to
     complete.

 (6) Stash the rxrpc_net pointer in the conn struct so that the rcu free
     routine can use it, even if the local endpoint has been freed.

Unfortunately, neither the timer nor the work item can simply get around
the problem by just using refcount_inc_not_zero() as the waits would still
have to be done, and there would still be the possibility of having to put
the ref in the expiration function.

Note the connection work item is mostly going to go away with the main
event work being transferred to the I/O thread, so the wait in (6) will
become obsolete.

Signed-off-by: David Howells 
cc: Marc Dionne 
cc: linux-afs@lists.infradead.org

rxrpc: Drop rxrpc_conn_parameters from rxrpc_connection and rxrpc_bundle

2022-12-01T13:36:38+00:00

Remove the rxrpc_conn_parameters struct from the rxrpc_connection and
rxrpc_bundle structs and emplace the members directly.  These are going to
get filled in from the rxrpc_call struct in future.

Signed-off-by: David Howells 
cc: Marc Dionne 
cc: linux-afs@lists.infradead.org