RDMA/mlx5: Fix mkey cache WQ flush

The cited patch tries to ensure no pending works on the mkey cache
workqueue by disabling adding new works and call flush_workqueue().
But this workqueue also has delayed works which might still be pending
the delay time to be queued.

Add cancel_delayed_work() for the delayed works which waits to be queued
and then the flush_workqueue() will flush all works which are already
queued and running.

Fixes: 374012b ("RDMA/mlx5: Fix mkey cache possible deadlock on cleanup")
Link: https://lore.kernel.org/r/b8722f14e7ed81452f791764a26d2ed4cfa11478.1698256179.git.leon@kernel.org
Signed-off-by: Moshe Shemesh <moshe@nvidia.com>
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

Author: mosheshemesh2

drivers/infiniband/hw/mlx5/mr.c

@@ -1000,11 +1000,13 @@ void mlx5_mkey_cache_cleanup(struct mlx5_ib_dev *dev)
 		return;
 
 	mutex_lock(&dev->cache.rb_lock);
+	cancel_delayed_work(&dev->cache.remove_ent_dwork);
 	for (node = rb_first(root); node; node = rb_next(node)) {
 		ent = rb_entry(node, struct mlx5_cache_ent, node);
 		spin_lock_irq(&ent->mkeys_queue.lock);
 		ent->disabled = true;
 		spin_unlock_irq(&ent->mkeys_queue.lock);
+		cancel_delayed_work(&ent->dwork);
 	}
 	mutex_unlock(&dev->cache.rb_lock);