RDMA/rtrs-srv: Destroy path files after making sure no IOs in-flight

[ Upstream commit c4d32e77 ]

Destroying path files may lead to the freeing of rdma_stats. This creates
the following race.

An IO is in-flight, or has just passed the session state check in
process_read/process_write. The close_work gets triggered and the function
rtrs_srv_close_work() starts and does destroy path which frees the
rdma_stats. After this the function process_read/process_write resumes and
tries to update the stats through the function rtrs_srv_update_rdma_stats

This commit solves the problem by moving the destroy path function to a
later point. This point makes sure any inflights are completed. This is
done by qp drain, and waiting for all in-flights through ops_id.

Fixes: 9cb83748

 ("RDMA/rtrs: server: main functionality")
Signed-off-by: Md Haris Iqbal <haris.iqbal@ionos.com>
Signed-off-by: Santosh Kumar Pradhan <santosh.pradhan@ionos.com>
Signed-off-by: Grzegorz Prajsner <grzegorz.prajsner@ionos.com>
Link: https://lore.kernel.org/r/20231120154146.920486-6-haris.iqbal@ionos.com
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>