IB/mlx5: Fix implicit ODP interrupted page fault

Since any page fault may be interrupted by a MMU invalidation and implicit
leaf MR may be released during this process. The check for parent value
is unreliable condition for an implicit MR.
Use other condition that we can rely on to determine if MR is implicit.

Fixes: b4cfe447 ("IB/mlx5: Implement on demand paging by adding support for MMU notifiers")
Signed-off-by: Artemy Kovalyov <artemyko@mellanox.com>
Signed-off-by: Moni Shoua <monis@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>

drivers/infiniband/hw/mlx5/odp.c

@@ -506,14 +506,13 @@ void mlx5_ib_free_implicit_mr(struct mlx5_ib_mr *imr)
 static int pagefault_mr(struct mlx5_ib_dev *dev, struct mlx5_ib_mr *mr,
 			u64 io_virt, size_t bcnt, u32 *bytes_mapped)
 {
+	int npages = 0, current_seq, page_shift, ret, np;
+	bool implicit = false;
 	struct ib_umem_odp *odp_mr = to_ib_umem_odp(mr->umem);
 	u64 access_mask = ODP_READ_ALLOWED_BIT;
-	int npages = 0, page_shift, np;
 	u64 start_idx, page_mask;
 	struct ib_umem_odp *odp;
-	int current_seq;
 	size_t size;
-	int ret;
 
 	if (!odp_mr->page_list) {
 		odp = implicit_mr_get_data(mr, io_virt, bcnt);
@@ -521,7 +520,7 @@ static int pagefault_mr(struct mlx5_ib_dev *dev, struct mlx5_ib_mr *mr,
 		if (IS_ERR(odp))
 			return PTR_ERR(odp);
 		mr = odp->private;
-
+		implicit = true;
 	} else {
 		odp = odp_mr;
 	}
@@ -600,7 +599,7 @@ static int pagefault_mr(struct mlx5_ib_dev *dev, struct mlx5_ib_mr *mr,
 
 out:
 	if (ret == -EAGAIN) {
-		if (mr->parent || !odp->dying) {
+		if (implicit || !odp->dying) {
 			unsigned long timeout =
 				msecs_to_jiffies(MMU_NOTIFIER_TIMEOUT);