[PATCH v2] powerpc/vas: Limit open window failure messages in log bufffer

[PATCH v2] powerpc/vas: Limit open window failure messages in log bufffer

[Haren Myneni]

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 <haren@linux.ibm.com>
---
 arch/powerpc/platforms/book3s/vas-api.c | 34 ++++++++++++-------------
 arch/powerpc/platforms/pseries/vas.c    |  4 +--
 2 files changed, 18 insertions(+), 20 deletions(-)

diff --git a/arch/powerpc/platforms/book3s/vas-api.c b/arch/powerpc/platforms/book3s/vas-api.c
index 77ea9335fd04..52dabbe52da1 100644
--- a/arch/powerpc/platforms/book3s/vas-api.c
+++ b/arch/powerpc/platforms/book3s/vas-api.c
@@ -4,6 +4,8 @@
  * 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>
@@ -78,7 +80,7 @@ int get_vas_user_win_ref(struct vas_user_win_ref *task_ref)
 	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;
 	}
@@ -235,8 +237,7 @@ void vas_update_csb(struct coprocessor_request_block *crb,
 	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)
@@ -294,7 +295,7 @@ static int coproc_ioc_tx_win_open(struct file *fp, unsigned long arg)
 
 	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;
 	}
 
@@ -311,7 +312,7 @@ static int coproc_ioc_tx_win_open(struct file *fp, unsigned long arg)
 	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);
 	}
@@ -405,8 +406,7 @@ static vm_fault_t vas_mmap_fault(struct vm_fault *vmf)
 	 * 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;
 	}
 
@@ -421,8 +421,7 @@ static vm_fault_t vas_mmap_fault(struct vm_fault *vmf)
 	 * 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;
 	}
 
@@ -481,19 +480,19 @@ static int coproc_mmap(struct file *fp, struct vm_area_struct *vma)
 	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;
 	}
 
@@ -510,14 +509,14 @@ static int coproc_mmap(struct file *fp, struct vm_area_struct *vma)
 	 */
 	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;
 	}
@@ -533,8 +532,8 @@ static int coproc_mmap(struct file *fp, struct vm_area_struct *vma)
 	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;
@@ -609,8 +608,7 @@ int vas_register_coproc_api(struct module *mod, enum vas_cop_type cop_type,
 		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;
 
diff --git a/arch/powerpc/platforms/pseries/vas.c b/arch/powerpc/platforms/pseries/vas.c
index 513180467562..88bee56ff92b 100644
--- a/arch/powerpc/platforms/pseries/vas.c
+++ b/arch/powerpc/platforms/pseries/vas.c
@@ -340,7 +340,7 @@ static struct vas_window *vas_allocate_window(int vas_id, u64 flags,
 
 	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;
 	}
@@ -423,7 +423,7 @@ static struct vas_window *vas_allocate_window(int vas_id, u64 flags,
 
 	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:
 	/*
-- 
2.26.3

Re: [PATCH v2] powerpc/vas: Limit open window failure messages in log bufffer

[Michael Ellerman]

On Thu, 19 Oct 2023 14:50:33 -0700, Haren Myneni wrote:
> 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.
> 
> [...]

Applied to powerpc/next.

[1/1] powerpc/vas: Limit open window failure messages in log bufffer
      https://git.kernel.org/powerpc/c/73b25505ce043b561028e5571d84dc82aa53c2b4

cheers