net/rds: Revert "RDS: add reconnect retry scheme for stalled connections"

net/rds: Revert "RDS: add reconnect retry scheme for stalled connections"

This reverts commit 5acb959ad59966b0b6905802ed720d26c560c3c5.

Commit "RDS: add reconnect retry scheme for stalled connections" introduces
the rds_reconnect_timeout to retry the connection establishment after
sysctl_reconnect_retry_ms (default is 1000ms). Nevertheless, this proactive
mechanism is overkilled and it is causing long brownout time in the
virtualized environment. In short, below are the justifications why commit
5acb959ad59966b0b6905802ed720d26c560c3c5 is reverted.

a) The retry counter starts ticking after RDS received an ADDR_CHANGE
event. After receiving an ADDR_CHANGE event, RDS needs to perform shutdown
via shutdown_worker. Then, initiate a new connection via connect_worker.
Eventually, a CM REQ is only sent out after rds received
RDMA_CM_EVENT_ADDR_RESOLVED and RDMA_CM_EVENT_ROUTE_RESOLVED events. If the
retry is made to cater for stalled connection due to missing CM messages,
the retry should only happen after a CM REQ is sent.  With the current
retry scheme (and with the default 1000 ms) that happens after ADDR_CHANGE
event, it introduces congestion in the single threaded workqueue.

b) Assuming that we modify the retry counter to start ticking after a CM
REQ message is sent out. By introducing another retry timeout, it
complicates the system tuning. Why? First, the sysctl_reconnect_retry_ms
relies on the underlying cma_response_timeout. Any modication of
cma_response_timeout requires to tune sysctl_reconnect_retry_ms. Second, it
is hard to find a universal timing that fits all configurations
(bare-metal, virtualized, mixed environment, and homo/heterogenous system).

Orabug: 25521901

Signed-off-by: Wei Lin Guay <wei.lin.guay@oracle.com>
Reviewed-by: Håkon Bugge <haakon.bugge@oracle.com>
Tested-by: Dib Chatterjee <dib.chatterjee@oracle.com>
Tested-by: Rosa Isela Lopez Romero <rosa.lopez@oracle.com>
Acked-by: Ajaykumar Hotchandani <ajaykumar.hotchandani@oracle.com>