net/mlx5: Convert mkey_table to XArray

The lock protecting the data structure does not need to be an rwlock.  The
only read access to the lock is in an error path, and if that's limiting
your scalability, you have bigger performance problems.

Eliminate mlx5_mkey_table in favour of using the xarray directly.
reg_mr_callback must use GFP_ATOMIC for allocating XArray nodes as it may
be called in interrupt context.

This also fixes a minor bug where SRCU locking was being used on the radix
tree read side, when RCU was needed too.

Signed-off-by: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>

4 files changed, 18 insertions, 28 deletions

diff --git a/drivers/infiniband/hw/mlx5/cq.c b/drivers/infiniband/hw/mlx5/cq.c
index 2e2e65f00257..0220736b073e 100644
--- a/drivers/infiniband/hw/mlx5/cq.c
+++ b/drivers/infiniband/hw/mlx5/cq.c
@@ -522,9 +522,9 @@ repoll:
 	case MLX5_CQE_SIG_ERR:
 		sig_err_cqe = (struct mlx5_sig_err_cqe *)cqe64;
 
-		read_lock(&dev->mdev->priv.mkey_table.lock);
-		mmkey = __mlx5_mr_lookup(dev->mdev,
-					 mlx5_base_mkey(be32_to_cpu(sig_err_cqe->mkey)));
+		xa_lock(&dev->mdev->priv.mkey_table);
+		mmkey = xa_load(&dev->mdev->priv.mkey_table,
+				mlx5_base_mkey(be32_to_cpu(sig_err_cqe->mkey)));
 		mr = to_mibmr(mmkey);
 		get_sig_err_item(sig_err_cqe, &mr->sig->err_item);
 		mr->sig->sig_err_exists = true;
@@ -537,7 +537,7 @@ repoll:
 			     mr->sig->err_item.expected,
 			     mr->sig->err_item.actual);
 
-		read_unlock(&dev->mdev->priv.mkey_table.lock);
+		xa_unlock(&dev->mdev->priv.mkey_table);
 		goto repoll;
 	}
 
diff --git a/drivers/infiniband/hw/mlx5/devx.c b/drivers/infiniband/hw/mlx5/devx.c
index 80b42d069328..931f587dfb8f 100644
--- a/drivers/infiniband/hw/mlx5/devx.c
+++ b/drivers/infiniband/hw/mlx5/devx.c
@@ -1043,13 +1043,10 @@ static int devx_handle_mkey_indirect(struct devx_obj *obj,
 				     struct mlx5_ib_dev *dev,
 				     void *in, void *out)
 {
-	struct mlx5_mkey_table *table = &dev->mdev->priv.mkey_table;
 	struct mlx5_ib_devx_mr *devx_mr = &obj->devx_mr;
-	unsigned long flags;
 	struct mlx5_core_mkey *mkey;
 	void *mkc;
 	u8 key;
-	int err;
 
 	mkey = &devx_mr->mmkey;
 	mkc = MLX5_ADDR_OF(create_mkey_in, in, memory_key_mkey_entry);
@@ -1062,11 +1059,8 @@ static int devx_handle_mkey_indirect(struct devx_obj *obj,
 	mkey->pd = MLX5_GET(mkc, mkc, pd);
 	devx_mr->ndescs = MLX5_GET(mkc, mkc, translations_octword_size);
 
-	write_lock_irqsave(&table->lock, flags);
-	err = radix_tree_insert(&table->tree, mlx5_base_mkey(mkey->key),
-				mkey);
-	write_unlock_irqrestore(&table->lock, flags);
-	return err;
+	return xa_err(xa_store(&dev->mdev->priv.mkey_table,
+			       mlx5_base_mkey(mkey->key), mkey, GFP_KERNEL));
 }
 
 static int devx_handle_mkey_create(struct mlx5_ib_dev *dev,
@@ -1117,12 +1111,8 @@ static void devx_free_indirect_mkey(struct rcu_head *rcu)
  */
 static void devx_cleanup_mkey(struct devx_obj *obj)
 {
-	struct mlx5_mkey_table *table = &obj->mdev->priv.mkey_table;
-	unsigned long flags;
-
-	write_lock_irqsave(&table->lock, flags);
-	radix_tree_delete(&table->tree, mlx5_base_mkey(obj->devx_mr.mmkey.key));
-	write_unlock_irqrestore(&table->lock, flags);
+	xa_erase(&obj->mdev->priv.mkey_table,
+		 mlx5_base_mkey(obj->devx_mr.mmkey.key));
 }
 
 static int devx_obj_cleanup(struct ib_uobject *uobject,
diff --git a/drivers/infiniband/hw/mlx5/mr.c b/drivers/infiniband/hw/mlx5/mr.c
index 5f09699fab98..83b452d977d4 100644
--- a/drivers/infiniband/hw/mlx5/mr.c
+++ b/drivers/infiniband/hw/mlx5/mr.c
@@ -130,7 +130,7 @@ static void reg_mr_callback(int status, struct mlx5_async_work *context)
 	struct mlx5_cache_ent *ent = &cache->ent[c];
 	u8 key;
 	unsigned long flags;
-	struct mlx5_mkey_table *table = &dev->mdev->priv.mkey_table;
+	struct xarray *mkeys = &dev->mdev->priv.mkey_table;
 	int err;
 
 	spin_lock_irqsave(&ent->lock, flags);
@@ -158,12 +158,12 @@ static void reg_mr_callback(int status, struct mlx5_async_work *context)
 	ent->size++;
 	spin_unlock_irqrestore(&ent->lock, flags);
 
-	write_lock_irqsave(&table->lock, flags);
-	err = radix_tree_insert(&table->tree, mlx5_base_mkey(mr->mmkey.key),
-				&mr->mmkey);
+	xa_lock_irqsave(mkeys, flags);
+	err = xa_err(__xa_store(mkeys, mlx5_base_mkey(mr->mmkey.key),
+				&mr->mmkey, GFP_ATOMIC));
+	xa_unlock_irqrestore(mkeys, flags);
 	if (err)
 		pr_err("Error inserting to mkey tree. 0x%x\n", -err);
-	write_unlock_irqrestore(&table->lock, flags);
 
 	if (!completion_done(&ent->compl))
 		complete(&ent->compl);
diff --git a/drivers/infiniband/hw/mlx5/odp.c b/drivers/infiniband/hw/mlx5/odp.c
index 12ccee1eb047..c594489eb2d7 100644
--- a/drivers/infiniband/hw/mlx5/odp.c
+++ b/drivers/infiniband/hw/mlx5/odp.c
@@ -768,7 +768,7 @@ static int pagefault_single_data_segment(struct mlx5_ib_dev *dev,
 	bcnt -= *bytes_committed;
 
 next_mr:
-	mmkey = __mlx5_mr_lookup(dev->mdev, mlx5_base_mkey(key));
+	mmkey = xa_load(&dev->mdev->priv.mkey_table, mlx5_base_mkey(key));
 	if (!mkey_is_eq(mmkey, key)) {
 		mlx5_ib_dbg(dev, "failed to find mkey %x\n", key);
 		ret = -EFAULT;
@@ -1686,8 +1686,8 @@ static void num_pending_prefetch_dec(struct mlx5_ib_dev *dev,
 		struct mlx5_core_mkey *mmkey;
 		struct mlx5_ib_mr *mr;
 
-		mmkey = __mlx5_mr_lookup(dev->mdev,
-					 mlx5_base_mkey(sg_list[i].lkey));
+		mmkey = xa_load(&dev->mdev->priv.mkey_table,
+				mlx5_base_mkey(sg_list[i].lkey));
 		mr = container_of(mmkey, struct mlx5_ib_mr, mmkey);
 		atomic_dec(&mr->num_pending_prefetch);
 	}
@@ -1706,8 +1706,8 @@ static bool num_pending_prefetch_inc(struct ib_pd *pd,
 		struct mlx5_core_mkey *mmkey;
 		struct mlx5_ib_mr *mr;
 
-		mmkey = __mlx5_mr_lookup(dev->mdev,
-					 mlx5_base_mkey(sg_list[i].lkey));
+		mmkey = xa_load(&dev->mdev->priv.mkey_table,
+				mlx5_base_mkey(sg_list[i].lkey));
 		if (!mmkey || mmkey->key != sg_list[i].lkey) {
 			ret = false;
 			break;