RDMA/i40iw: Avoid panic when objects are being created and destroyed

A panic occurs when there is a newly-registered element on the QP/CQ MR
list waiting to be attached, but a different MR is deregistered. The
current code only checks for whether the list is empty, not whether the
element being deregistered is actually on the list.

Fix the panic by adding a boolean to track if the object is on the list.

Fixes: d37498417947 ("i40iw: add files for iwarp interface")
Signed-off-by: Andrew Boyer <andrew.boyer@dell.com>
Reviewed-by: Shiraz Saleem <shiraz.saleem@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>

drivers/infiniband/hw/i40iw/i40iw_verbs.c

@@ -394,6 +394,7 @@ static struct i40iw_pbl *i40iw_get_pbl(unsigned long va,
 
 	list_for_each_entry(iwpbl, pbl_list, list) {
 		if (iwpbl->user_base == va) {
+			iwpbl->on_list = false;
 			list_del(&iwpbl->list);
 			return iwpbl;
 		}
@@ -1898,6 +1899,7 @@ static struct ib_mr *i40iw_reg_user_mr(struct ib_pd *pd,
 			goto error;
 		spin_lock_irqsave(&ucontext->qp_reg_mem_list_lock, flags);
 		list_add_tail(&iwpbl->list, &ucontext->qp_reg_mem_list);
+		iwpbl->on_list = true;
 		spin_unlock_irqrestore(&ucontext->qp_reg_mem_list_lock, flags);
 		break;
 	case IW_MEMREG_TYPE_CQ:
@@ -1908,6 +1910,7 @@ static struct ib_mr *i40iw_reg_user_mr(struct ib_pd *pd,
 
 		spin_lock_irqsave(&ucontext->cq_reg_mem_list_lock, flags);
 		list_add_tail(&iwpbl->list, &ucontext->cq_reg_mem_list);
+		iwpbl->on_list = true;
 		spin_unlock_irqrestore(&ucontext->cq_reg_mem_list_lock, flags);
 		break;
 	case IW_MEMREG_TYPE_MEM:
@@ -2045,14 +2048,18 @@ static void i40iw_del_memlist(struct i40iw_mr *iwmr,
 	switch (iwmr->type) {
 	case IW_MEMREG_TYPE_CQ:
 		spin_lock_irqsave(&ucontext->cq_reg_mem_list_lock, flags);
-		if (!list_empty(&ucontext->cq_reg_mem_list))
+		if (iwpbl->on_list) {
+			iwpbl->on_list = false;
 			list_del(&iwpbl->list);
+		}
 		spin_unlock_irqrestore(&ucontext->cq_reg_mem_list_lock, flags);
 		break;
 	case IW_MEMREG_TYPE_QP:
 		spin_lock_irqsave(&ucontext->qp_reg_mem_list_lock, flags);
-		if (!list_empty(&ucontext->qp_reg_mem_list))
+		if (iwpbl->on_list) {
+			iwpbl->on_list = false;
 			list_del(&iwpbl->list);
+		}
 		spin_unlock_irqrestore(&ucontext->qp_reg_mem_list_lock, flags);
 		break;
 	default:

drivers/infiniband/hw/i40iw/i40iw_verbs.h

@@ -78,6 +78,7 @@ struct i40iw_pbl {
 	};
 
 	bool pbl_allocated;
+	bool on_list;
 	u64 user_base;
 	struct i40iw_pble_alloc pble_alloc;
 	struct i40iw_mr *iwmr;