SUNRPC: The TCP back channel mustn't disappear while requests are outstanding
If there are TCP back channel requests being processed by the
server threads, then we should hold a reference to the transport
to ensure it doesn't get freed from underneath us.
Reported-by: Neil Brown <neilb@suse.de> Fixes: 2ea24497a1b3 ("SUNRPC: RPC callbacks may be split across several..") Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com> Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>