RDMA/rtrs-clt: Check state of the rtrs_clt_sess before reading its stats

When get_next_path_min_inflight is called to select the next path, it
iterates over the list of available rtrs_clt_sess (paths). It then reads
the number of inflight IOs for that path to select one which has the least
inflight IO.

But it may so happen that rtrs_clt_sess (path) is no longer in the
connected state because closing or error recovery paths can change the status
of the rtrs_clt_Sess.

For example, the client sent the heart-beat and did not get the
response, it would change the session status and stop IO processing.
The added checking of this patch can prevent accessing the broken path
and generating duplicated error messages.

It is ok if the status is changed after checking the status because
the error recovery path does not free memory and only tries to
reconnection. And also it is ok if the session is closed after checking
the status because closing the session changes the session status and
flush all IO beforing free memory. If the session is being accessed for
IO processing, the closing session will wait.

Fixes: 6a98d71d ("RDMA/rtrs: client: main functionality")
Link: https://lore.kernel.org/r/20210528113018.52290-13-jinpu.wang@ionos.comSigned-off-by: Md Haris Iqbal <haris.iqbal@ionos.com>
Reviewed-by: Gioh Kim <gi-oh.kim@ionos.com>
Signed-off-by: Gioh Kim <gi-oh.kim@ionos.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

drivers/infiniband/ulp/rtrs/rtrs-clt.c

@@ -813,6 +813,9 @@ static struct rtrs_clt_sess *get_next_path_min_inflight(struct path_it *it)
 	int inflight;
 
 	list_for_each_entry_rcu(sess, &clt->paths_list, s.entry) {
+		if (unlikely(READ_ONCE(sess->state) != RTRS_CLT_CONNECTED))
+			continue;
+
 		if (unlikely(!list_empty(raw_cpu_ptr(sess->mp_skip_entry))))
 			continue;