powerpc/vas: Limit open window failure messages in log bufffer

The VAS open window call prints error message and returns -EBUSY
after the migration suspend event initiated and until the resume
event completed on the destination system. It can cause the log
buffer filled with these error messages if the user space issues
continuous open window calls. Similar case even for DLPAR CPU
remove event when no credits are available until the credits are
freed or with the other DLPAR CPU add event.

So changes in the patch to use pr_err_ratelimited() instead of
pr_err() to display open window failure and not-available credits
error messages.

Use pr_fmt() and make the corresponding changes to have the
consistencein prefix all pr_*() messages (vas-api.c).

Fixes: 37e6764895ef ("powerpc/pseries/vas: Add VAS migration handler")
Signed-off-by: Haren Myneni <[e-mail]>
[mpe: Use "vas-api" as the prefix to match the file name.]
Signed-off-by: Michael Ellerman <[e-mail]>
Link: https://msgid.link/[e-mail]

arch/powerpc/platforms/book3s/vas-api.c

···
  * Copyright (C) 2019 Haren Myneni, IBM Corp
  */
 
+#define pr_fmt(fmt)	"vas-api: " fmt
+
 #include <linux/kernel.h>
 #include <linux/device.h>
 #include <linux/cdev.h>
···
 	task_ref->mm = get_task_mm(current);
 	if (!task_ref->mm) {
 		put_pid(task_ref->pid);
-		pr_err("VAS: pid(%d): mm_struct is not found\n",
+		pr_err("pid(%d): mm_struct is not found\n",
 				current->pid);
 		return -EPERM;
 	}
···
 	rc = kill_pid_info(SIGSEGV, &info, pid);
 	rcu_read_unlock();
 
-	pr_devel("%s(): pid %d kill_proc_info() rc %d\n", __func__,
-			pid_vnr(pid), rc);
+	pr_devel("pid %d kill_proc_info() rc %d\n", pid_vnr(pid), rc);
 }
 
 void vas_dump_crb(struct coprocessor_request_block *crb)
···
 
 	rc = copy_from_user(&uattr, uptr, sizeof(uattr));
 	if (rc) {
-		pr_err("%s(): copy_from_user() returns %d\n", __func__, rc);
+		pr_err("copy_from_user() returns %d\n", rc);
 		return -EFAULT;
 	}
 
···
 	txwin = cp_inst->coproc->vops->open_win(uattr.vas_id, uattr.flags,
 						cp_inst->coproc->cop_type);
 	if (IS_ERR(txwin)) {
-		pr_err("%s() VAS window open failed, %ld\n", __func__,
+		pr_err_ratelimited("VAS window open failed rc=%ld\n",
 				PTR_ERR(txwin));
 		return PTR_ERR(txwin);
 	}
···
 	 * window is not opened. Shouldn't expect this error.
 	 */
 	if (!cp_inst || !cp_inst->txwin) {
-		pr_err("%s(): Unexpected fault on paste address with TX window closed\n",
-				__func__);
+		pr_err("Unexpected fault on paste address with TX window closed\n");
 		return VM_FAULT_SIGBUS;
 	}
 
···
 	 * issue NX request.
 	 */
 	if (txwin->task_ref.vma != vmf->vma) {
-		pr_err("%s(): No previous mapping with paste address\n",
-			__func__);
+		pr_err("No previous mapping with paste address\n");
 		return VM_FAULT_SIGBUS;
 	}
 
···
 	txwin = cp_inst->txwin;
 
 	if ((vma->vm_end - vma->vm_start) > PAGE_SIZE) {
-		pr_debug("%s(): size 0x%zx, PAGE_SIZE 0x%zx\n", __func__,
+		pr_debug("size 0x%zx, PAGE_SIZE 0x%zx\n",
 				(vma->vm_end - vma->vm_start), PAGE_SIZE);
 		return -EINVAL;
 	}
 
 	/* Ensure instance has an open send window */
 	if (!txwin) {
-		pr_err("%s(): No send window open?\n", __func__);
+		pr_err("No send window open?\n");
 		return -EINVAL;
 	}
 
 	if (!cp_inst->coproc->vops || !cp_inst->coproc->vops->paste_addr) {
-		pr_err("%s(): VAS API is not registered\n", __func__);
+		pr_err("VAS API is not registered\n");
 		return -EACCES;
 	}
 
···
 	 */
 	mutex_lock(&txwin->task_ref.mmap_mutex);
 	if (txwin->status != VAS_WIN_ACTIVE) {
-		pr_err("%s(): Window is not active\n", __func__);
+		pr_err("Window is not active\n");
 		rc = -EACCES;
 		goto out;
 	}
 
 	paste_addr = cp_inst->coproc->vops->paste_addr(txwin);
 	if (!paste_addr) {
-		pr_err("%s(): Window paste address failed\n", __func__);
+		pr_err("Window paste address failed\n");
 		rc = -EINVAL;
 		goto out;
 	}
···
 	rc = remap_pfn_range(vma, vma->vm_start, pfn + vma->vm_pgoff,
 			vma->vm_end - vma->vm_start, prot);
 
-	pr_devel("%s(): paste addr %llx at %lx, rc %d\n", __func__,
-			paste_addr, vma->vm_start, rc);
+	pr_devel("paste addr %llx at %lx, rc %d\n", paste_addr,
+			vma->vm_start, rc);
 
 	txwin->task_ref.vma = vma;
 	vma->vm_ops = &vas_vm_ops;
···
 		goto err;
 	}
 
-	pr_devel("%s: Added dev [%d,%d]\n", __func__, MAJOR(devno),
-			MINOR(devno));
+	pr_devel("Added dev [%d,%d]\n", MAJOR(devno), MINOR(devno));
 
 	return 0;
 

arch/powerpc/platforms/pseries/vas.c

···
 
 	if (atomic_inc_return(&cop_feat_caps->nr_used_credits) >
 			atomic_read(&cop_feat_caps->nr_total_credits)) {
-		pr_err("Credits are not available to allocate window\n");
+		pr_err_ratelimited("Credits are not available to allocate window\n");
 		rc = -EINVAL;
 		goto out;
 	}
···
 
 	put_vas_user_win_ref(&txwin->vas_win.task_ref);
 	rc = -EBUSY;
-	pr_err("No credit is available to allocate window\n");
+	pr_err_ratelimited("No credit is available to allocate window\n");
 
 out_free:
 	/*