RDMA/mlx5: Replace spinlock protected write with atomic var

mkey variant calculation was spinlock protected to make it atomic, replace
that with one atomic variable.

Link: https://lore.kernel.org/r/20200310082238.239865-4-leon@kernel.org
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

drivers/infiniband/hw/mlx5/main.c

@@ -6390,7 +6390,7 @@ static int mlx5_ib_stage_init_init(struct mlx5_ib_dev *dev)
 	spin_lock_init(&dev->reset_flow_resource_lock);
 	xa_init(&dev->odp_mkeys);
 	xa_init(&dev->sig_mrs);
-	spin_lock_init(&dev->mkey_lock);
+	atomic_set(&dev->mkey_var, 0);
 
 	spin_lock_init(&dev->dm.lock);
 	dev->dm.dev = mdev;

drivers/infiniband/hw/mlx5/mlx5_ib.h

@@ -993,10 +993,7 @@ struct mlx5_ib_dev {
 	 */
 	struct mlx5_ib_resources	devr;
 
-	/* protect mkey key part */
-	spinlock_t			mkey_lock;
-	u8				mkey_key;
-
+	atomic_t			mkey_var;
 	struct mlx5_mr_cache		cache;
 	struct timer_list		delay_timer;
 	/* Prevents soft lock on massive reg MRs */

drivers/infiniband/hw/mlx5/mr.c

@@ -54,12 +54,8 @@ static void
 assign_mkey_variant(struct mlx5_ib_dev *dev, struct mlx5_core_mkey *mkey,
 		    u32 *in)
 {
+	u8 key = atomic_inc_return(&dev->mkey_var);
 	void *mkc;
-	u8 key;
-
-	spin_lock_irq(&dev->mkey_lock);
-	key = dev->mkey_key++;
-	spin_unlock_irq(&dev->mkey_lock);
 
 	mkc = MLX5_ADDR_OF(create_mkey_in, in, memory_key_mkey_entry);
 	MLX5_SET(mkc, mkc, mkey_7_0, key);