RDMA/mlx5: Use a dedicated mkey xarray for ODP

There is a per device xarray storing mkeys that is used to store every
mkey in the system. However, this xarray is now only read by ODP for
certain ODP designated MRs (ODP, implicit ODP, MW, DEVX_INDIRECT).

Create an xarray only for use by ODP, that only contains ODP related
MKeys. This xarray is protected by SRCU and all erases are protected by a
synchronize.

This improves performance:

 - All MRs in the odp_mkeys xarray are ODP MRs, so some tests for is_odp()
   can be deleted. The xarray will also consume fewer nodes.

 - normal MR's are never mixed with ODP MRs in a SRCU data structure so
   performance sucking synchronize_srcu() on every MR destruction is not
   needed.

 - No smp_load_acquire(live) and xa_load() double barrier on read

Due to the SRCU locking scheme care must be taken with the placement of
the xa_store(). Once it completes the MR is immediately visible to other
threads and only through a xa_erase() & synchronize_srcu() cycle could it
be destroyed.

Link: https://lore.kernel.org/r/20191009160934.3143-4-jgg@ziepe.ca
Reviewed-by: Artemy Kovalyov <artemyko@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

1 files changed, 23 insertions, 20 deletions

diff --git a/drivers/infiniband/hw/mlx5/mr.c b/drivers/infiniband/hw/mlx5/mr.c
index fd24640606c1..60b12dc53004 100644
--- a/drivers/infiniband/hw/mlx5/mr.c
+++ b/drivers/infiniband/hw/mlx5/mr.c
@@ -59,13 +59,9 @@ static bool umr_can_use_indirect_mkey(struct mlx5_ib_dev *dev)
 
 static int destroy_mkey(struct mlx5_ib_dev *dev, struct mlx5_ib_mr *mr)
 {
-	int err = mlx5_core_destroy_mkey(dev->mdev, &mr->mmkey);
+	WARN_ON(xa_load(&dev->odp_mkeys, mlx5_base_mkey(mr->mmkey.key)));
 
-	if (IS_ENABLED(CONFIG_INFINIBAND_ON_DEMAND_PAGING))
-		/* Wait until all page fault handlers using the mr complete. */
-		synchronize_srcu(&dev->mr_srcu);
-
-	return err;
+	return mlx5_core_destroy_mkey(dev->mdev, &mr->mmkey);
 }
 
 static int order2idx(struct mlx5_ib_dev *dev, int order)
@@ -218,9 +214,6 @@ static void remove_keys(struct mlx5_ib_dev *dev, int c, int num)
 		mlx5_core_destroy_mkey(dev->mdev, &mr->mmkey);
 	}
 
-	if (IS_ENABLED(CONFIG_INFINIBAND_ON_DEMAND_PAGING))
-		synchronize_srcu(&dev->mr_srcu);
-
 	list_for_each_entry_safe(mr, tmp_mr, &del_list, list) {
 		list_del(&mr->list);
 		kfree(mr);
@@ -555,10 +548,6 @@ static void clean_keys(struct mlx5_ib_dev *dev, int c)
 		mlx5_core_destroy_mkey(dev->mdev, &mr->mmkey);
 	}
 
-#ifdef CONFIG_INFINIBAND_ON_DEMAND_PAGING
-	synchronize_srcu(&dev->mr_srcu);
-#endif
-
 	list_for_each_entry_safe(mr, tmp_mr, &del_list, list) {
 		list_del(&mr->list);
 		kfree(mr);
@@ -1338,9 +1327,14 @@ struct ib_mr *mlx5_ib_reg_user_mr(struct ib_pd *pd, u64 start, u64 length,
 	if (is_odp_mr(mr)) {
 		to_ib_umem_odp(mr->umem)->private = mr;
 		atomic_set(&mr->num_pending_prefetch, 0);
+		err = xa_err(xa_store(&dev->odp_mkeys,
+				      mlx5_base_mkey(mr->mmkey.key), &mr->mmkey,
+				      GFP_KERNEL));
+		if (err) {
+			dereg_mr(dev, mr);
+			return ERR_PTR(err);
+		}
 	}
-	if (IS_ENABLED(CONFIG_INFINIBAND_ON_DEMAND_PAGING))
-		smp_store_release(&mr->live, 1);
 
 	return &mr->ibmr;
 error:
@@ -1582,10 +1576,10 @@ static void dereg_mr(struct mlx5_ib_dev *dev, struct mlx5_ib_mr *mr)
 		/* Prevent new page faults and
 		 * prefetch requests from succeeding
 		 */
-		WRITE_ONCE(mr->live, 0);
+		xa_erase(&dev->odp_mkeys, mlx5_base_mkey(mr->mmkey.key));
 
 		/* Wait for all running page-fault handlers to finish. */
-		synchronize_srcu(&dev->mr_srcu);
+		synchronize_srcu(&dev->odp_srcu);
 
 		/* dequeue pending prefetch requests for the mr */
 		if (atomic_read(&mr->num_pending_prefetch))
@@ -1959,9 +1953,19 @@ struct ib_mw *mlx5_ib_alloc_mw(struct ib_pd *pd, enum ib_mw_type type,
 		}
 	}
 
+	if (IS_ENABLED(CONFIG_INFINIBAND_ON_DEMAND_PAGING)) {
+		err = xa_err(xa_store(&dev->odp_mkeys,
+				      mlx5_base_mkey(mw->mmkey.key), &mw->mmkey,
+				      GFP_KERNEL));
+		if (err)
+			goto free_mkey;
+	}
+
 	kfree(in);
 	return &mw->ibmw;
 
+free_mkey:
+	mlx5_core_destroy_mkey(dev->mdev, &mw->mmkey);
 free:
 	kfree(mw);
 	kfree(in);
@@ -1975,13 +1979,12 @@ int mlx5_ib_dealloc_mw(struct ib_mw *mw)
 	int err;
 
 	if (IS_ENABLED(CONFIG_INFINIBAND_ON_DEMAND_PAGING)) {
-		xa_erase(&dev->mdev->priv.mkey_table,
-			 mlx5_base_mkey(mmw->mmkey.key));
+		xa_erase(&dev->odp_mkeys, mlx5_base_mkey(mmw->mmkey.key));
 		/*
 		 * pagefault_single_data_segment() may be accessing mmw under
 		 * SRCU if the user bound an ODP MR to this MW.
 		 */
-		synchronize_srcu(&dev->mr_srcu);
+		synchronize_srcu(&dev->odp_srcu);
 	}
 
 	err = mlx5_core_destroy_mkey(dev->mdev, &mmw->mmkey);