RDMA/ucontext: Get rid of the old disassociate flow

The disassociate_ucontext function in every driver is now empty, so we
don't need this ugly and wrong code that was messing with tgids.

rdma_user_mmap_io does this same work in a better way.
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>

drivers/infiniband/core/rdma_core.c

@@ -794,44 +794,6 @@ void uverbs_close_fd(struct file *f)
 	uverbs_uobject_put(uobj);
 }
 
-static void ufile_disassociate_ucontext(struct ib_ucontext *ibcontext)
-{
-	struct ib_device *ib_dev = ibcontext->device;
-	struct task_struct *owning_process  = NULL;
-	struct mm_struct   *owning_mm       = NULL;
-
-	owning_process = get_pid_task(ibcontext->tgid, PIDTYPE_PID);
-	if (!owning_process)
-		return;
-
-	owning_mm = get_task_mm(owning_process);
-	if (!owning_mm) {
-		pr_info("no mm, disassociate ucontext is pending task termination\n");
-		while (1) {
-			put_task_struct(owning_process);
-			usleep_range(1000, 2000);
-			owning_process = get_pid_task(ibcontext->tgid,
-						      PIDTYPE_PID);
-			if (!owning_process ||
-			    owning_process->state == TASK_DEAD) {
-				pr_info("disassociate ucontext done, task was terminated\n");
-				/* in case task was dead need to release the
-				 * task struct.
-				 */
-				if (owning_process)
-					put_task_struct(owning_process);
-				return;
-			}
-		}
-	}
-
-	down_write(&owning_mm->mmap_sem);
-	ib_dev->disassociate_ucontext(ibcontext);
-	up_write(&owning_mm->mmap_sem);
-	mmput(owning_mm);
-	put_task_struct(owning_process);
-}
-
 /*
  * Drop the ucontext off the ufile and completely disconnect it from the
  * ib_device
@@ -840,22 +802,29 @@ static void ufile_destroy_ucontext(struct ib_uverbs_file *ufile,
 				   enum rdma_remove_reason reason)
 {
 	struct ib_ucontext *ucontext = ufile->ucontext;
+	struct ib_device *ib_dev = ucontext->device;
 	int ret;
 
+	/*
+	 * If we are closing the FD then the user mmap VMAs must have
+	 * already been destroyed as they hold on to the filep, otherwise
+	 * they need to be zap'd.
+	 */
 	if (reason == RDMA_REMOVE_DRIVER_REMOVE) {
 		uverbs_user_mmap_disassociate(ufile);
-		ufile_disassociate_ucontext(ucontext);
+		if (ib_dev->disassociate_ucontext)
+			ib_dev->disassociate_ucontext(ucontext);
 	}
 
 	put_pid(ucontext->tgid);
-	ib_rdmacg_uncharge(&ucontext->cg_obj, ucontext->device,
+	ib_rdmacg_uncharge(&ucontext->cg_obj, ib_dev,
 			   RDMACG_RESOURCE_HCA_HANDLE);
 
 	/*
 	 * FIXME: Drivers are not permitted to fail dealloc_ucontext, remove
 	 * the error return.
 	 */
-	ret = ucontext->device->dealloc_ucontext(ucontext);
+	ret = ib_dev->dealloc_ucontext(ucontext);
 	WARN_ON(ret);
 
 	ufile->ucontext = NULL;