SUNRPC: Fix a hang in TLS sock_close if sk_write_pending

JIRA: https://issues.redhat.com/browse/RHEL-60028

commit 675d456
Author: Benjamin Coddington <bcodding@redhat.com>
Date:   Mon Nov 4 17:11:27 2024 -0500

    SUNRPC: Fix a hang in TLS sock_close if sk_write_pending

    We've observed an NFS server shrink the TCP window and then reset the TCP
    connection as part of a HA failover.  When the connection has TLS, often
    the NFS client will hang indefinitely in this stack:

         wait_woken+0x70/0x80
         wait_on_pending_writer+0xe4/0x110 [tls]
         tls_sk_proto_close+0x368/0x3a0 [tls]
         inet_release+0x54/0xb0
         __sock_release+0x48/0xc8
         sock_close+0x20/0x38
         __fput+0xe0/0x2f0
         __fput_sync+0x58/0x70
         xs_reset_transport+0xe8/0x1f8 [sunrpc]
         xs_tcp_shutdown+0xa4/0x190 [sunrpc]
         xprt_autoclose+0x68/0x170 [sunrpc]
         process_one_work+0x180/0x420
         worker_thread+0x258/0x368
         kthread+0x104/0x118
         ret_from_fork+0x10/0x20

    This hang prevents the client from closing the socket and reconnecting to
    the server.

    Because xs_nospace() elevates sk_write_pending, and sk_sndtimeo is
    MAX_SCHEDULE_TIMEOUT, tls_sk_proto_close is never able to complete its wait
    for pending writes to the socket.  For this case where we are resetting the
    transport anyway, we don't expect the socket to ever have write space, so
    fix this by simply clearing the sock's sndtimeo under the sock's lock.

    Signed-off-by: Benjamin Coddington <bcodding@redhat.com>
    Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

Signed-off-by: Benjamin Coddington <bcodding@redhat.com>

Author: bcodding-rh

net/sunrpc/xprtsock.c

@@ -1288,6 +1288,7 @@ static void xs_reset_transport(struct sock_xprt *transport)
 	transport->file = NULL;
 
 	sk->sk_user_data = NULL;
+	sk->sk_sndtimeo = 0;
 
 	xs_restore_old_callbacks(transport, sk);
 	xprt_clear_connected(xprt);