trace/hwlat: Use trace_min_max_param for width and window params

Use the trace_min_max_param to reduce code duplication.

No functional change.

Link: https://lkml.kernel.org/r/b91accd5a7c6c14ea02d3379aae974ba22b47dd6.1624372313.git.bristot@redhat.com

Cc: Phil Auld <pauld@redhat.com>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Kate Carcia <kcarcia@redhat.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Alexandre Chartre <alexandre.chartre@oracle.com>
Cc: Clark Willaims <williams@redhat.com>
Cc: John Kacur <jkacur@redhat.com>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: x86@kernel.org
Cc: linux-doc@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Daniel Bristot de Oliveira <bristot@redhat.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

kernel/trace/trace_hwlat.c

@@ -527,115 +527,6 @@ static int start_per_cpu_kthreads(struct trace_array *tr)
 	return retval;
 }
 
-/*
- * hwlat_read - Wrapper read function for reading both window and width
- * @filp: The active open file structure
- * @ubuf: The userspace provided buffer to read value into
- * @cnt: The maximum number of bytes to read
- * @ppos: The current "file" position
- *
- * This function provides a generic read implementation for the global state
- * "hwlat_data" structure filesystem entries.
- */
-static ssize_t hwlat_read(struct file *filp, char __user *ubuf,
-			  size_t cnt, loff_t *ppos)
-{
-	char buf[U64STR_SIZE];
-	u64 *entry = filp->private_data;
-	u64 val;
-	int len;
-
-	if (!entry)
-		return -EFAULT;
-
-	if (cnt > sizeof(buf))
-		cnt = sizeof(buf);
-
-	val = *entry;
-
-	len = snprintf(buf, sizeof(buf), "%llu\n", val);
-
-	return simple_read_from_buffer(ubuf, cnt, ppos, buf, len);
-}
-
-/**
- * hwlat_width_write - Write function for "width" entry
- * @filp: The active open file structure
- * @ubuf: The user buffer that contains the value to write
- * @cnt: The maximum number of bytes to write to "file"
- * @ppos: The current position in @file
- *
- * This function provides a write implementation for the "width" interface
- * to the hardware latency detector. It can be used to configure
- * for how many us of the total window us we will actively sample for any
- * hardware-induced latency periods. Obviously, it is not possible to
- * sample constantly and have the system respond to a sample reader, or,
- * worse, without having the system appear to have gone out to lunch. It
- * is enforced that width is less that the total window size.
- */
-static ssize_t
-hwlat_width_write(struct file *filp, const char __user *ubuf,
-		  size_t cnt, loff_t *ppos)
-{
-	u64 val;
-	int err;
-
-	err = kstrtoull_from_user(ubuf, cnt, 10, &val);
-	if (err)
-		return err;
-
-	mutex_lock(&hwlat_data.lock);
-	if (val < hwlat_data.sample_window)
-		hwlat_data.sample_width = val;
-	else
-		err = -EINVAL;
-	mutex_unlock(&hwlat_data.lock);
-
-	if (err)
-		return err;
-
-	return cnt;
-}
-
-/**
- * hwlat_window_write - Write function for "window" entry
- * @filp: The active open file structure
- * @ubuf: The user buffer that contains the value to write
- * @cnt: The maximum number of bytes to write to "file"
- * @ppos: The current position in @file
- *
- * This function provides a write implementation for the "window" interface
- * to the hardware latency detector. The window is the total time
- * in us that will be considered one sample period. Conceptually, windows
- * occur back-to-back and contain a sample width period during which
- * actual sampling occurs. Can be used to write a new total window size. It
- * is enforced that any value written must be greater than the sample width
- * size, or an error results.
- */
-static ssize_t
-hwlat_window_write(struct file *filp, const char __user *ubuf,
-		   size_t cnt, loff_t *ppos)
-{
-	u64 val;
-	int err;
-
-	err = kstrtoull_from_user(ubuf, cnt, 10, &val);
-	if (err)
-		return err;
-
-	mutex_lock(&hwlat_data.lock);
-	if (hwlat_data.sample_width < val)
-		hwlat_data.sample_window = val;
-	else
-		err = -EINVAL;
-	mutex_unlock(&hwlat_data.lock);
-
-	if (err)
-		return err;
-
-	return cnt;
-}
-
 static void *s_mode_start(struct seq_file *s, loff_t *pos)
 {
 	int mode = *pos;
@@ -760,16 +651,28 @@ static ssize_t hwlat_mode_write(struct file *filp, const char __user *ubuf,
 	return ret;
 }
 
-static const struct file_operations width_fops = {
-	.open		= tracing_open_generic,
-	.read		= hwlat_read,
-	.write		= hwlat_width_write,
+/*
+ * The width parameter is read/write using the generic trace_min_max_param
+ * method. The *val is protected by the hwlat_data lock and is upper
+ * bounded by the window parameter.
+ */
+static struct trace_min_max_param hwlat_width = {
+	.lock		= &hwlat_data.lock,
+	.val		= &hwlat_data.sample_width,
+	.max		= &hwlat_data.sample_window,
+	.min		= NULL,
 };
 
-static const struct file_operations window_fops = {
-	.open		= tracing_open_generic,
-	.read		= hwlat_read,
-	.write		= hwlat_window_write,
+/*
+ * The window parameter is read/write using the generic trace_min_max_param
+ * method. The *val is protected by the hwlat_data lock and is lower
+ * bounded by the width parameter.
+ */
+static struct trace_min_max_param hwlat_window = {
+	.lock		= &hwlat_data.lock,
+	.val		= &hwlat_data.sample_window,
+	.max		= NULL,
+	.min		= &hwlat_data.sample_width,
 };
 
 static const struct file_operations thread_mode_fops = {
@@ -802,15 +705,15 @@ static int init_tracefs(void)
 
 	hwlat_sample_window = tracefs_create_file("window", 0640,
 						  top_dir,
-						  &hwlat_data.sample_window,
-						  &window_fops);
+						  &hwlat_window,
+						  &trace_min_max_fops);
 	if (!hwlat_sample_window)
 		goto err;
 
 	hwlat_sample_width = tracefs_create_file("width", 0644,
 						 top_dir,
-						 &hwlat_data.sample_width,
-						 &width_fops);
+						 &hwlat_width,
+						 &trace_min_max_fops);
 	if (!hwlat_sample_width)
 		goto err;