tracing: Use seq file for trace_options

Code simplification for reading trace_options.

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
LKML-reference: <4B1DC4EF.3090106@cn.fujitsu.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>

1 files changed, 17 insertions, 43 deletions

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 88bd9ae2a9ed..a6c41cc63285 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -2316,67 +2316,32 @@ static const struct file_operations tracing_cpumask_fops = {
         .write          = tracing_cpumask_write,
 };
 
-static ssize_t
-tracing_trace_options_read(struct file *filp, char __user *ubuf,
-                       size_t cnt, loff_t *ppos)
+static int tracing_trace_options_show(struct seq_file *m, void *v)
 {
         struct tracer_opt *trace_opts;
         u32 tracer_flags;
-        int len = 0;
-        char *buf;
-        int r = 0;
         int i;
 
-
-        /* calculate max size */
-        for (i = 0; trace_options[i]; i++) {
-                len += strlen(trace_options[i]);
-                len += 3; /* "no" and newline */
-        }
-
         mutex_lock(&trace_types_lock);
         tracer_flags = current_trace->flags->val;
         trace_opts = current_trace->flags->opts;
 
-        /*
-         * Increase the size with names of options specific
-         * of the current tracer.
-         */
-        for (i = 0; trace_opts[i].name; i++) {
-                len += strlen(trace_opts[i].name);
-                len += 3; /* "no" and newline */
-        }
-
-        /* +1 for \0 */
-        buf = kmalloc(len + 1, GFP_KERNEL);
-        if (!buf) {
-                mutex_unlock(&trace_types_lock);
-                return -ENOMEM;
-        }
-
         for (i = 0; trace_options[i]; i++) {
                 if (trace_flags & (1 << i))
-                        r += sprintf(buf + r, "%s\n", trace_options[i]);
+                        seq_printf(m, "%s\n", trace_options[i]);
                 else
-                        r += sprintf(buf + r, "no%s\n", trace_options[i]);
+                        seq_printf(m, "no%s\n", trace_options[i]);
         }
 
         for (i = 0; trace_opts[i].name; i++) {
                 if (tracer_flags & trace_opts[i].bit)
-                        r += sprintf(buf + r, "%s\n",
-                                trace_opts[i].name);
+                        seq_printf(m, "%s\n", trace_opts[i].name);
                 else
-                        r += sprintf(buf + r, "no%s\n",
-                                trace_opts[i].name);
+                        seq_printf(m, "no%s\n", trace_opts[i].name);
         }
         mutex_unlock(&trace_types_lock);
 
-        WARN_ON(r >= len + 1);
-
-        r = simple_read_from_buffer(ubuf, cnt, ppos, buf, r);
-
-        kfree(buf);
-        return r;
+        return 0;
 }
 
 /* Try to assign a tracer specific option */
@@ -2471,9 +2436,18 @@ tracing_trace_options_write(struct file *filp, const char __user *ubuf,
         return cnt;
 }
 
+static int tracing_trace_options_open(struct inode *inode, struct file *file)
+{
+        if (tracing_disabled)
+                return -ENODEV;
+        return single_open(file, tracing_trace_options_show, NULL);
+}
+
 static const struct file_operations tracing_iter_fops = {
-        .open           = tracing_open_generic,
-        .read           = tracing_trace_options_read,
+        .open           = tracing_trace_options_open,
+        .read           = seq_read,
+        .llseek         = seq_lseek,
+        .release        = single_release,
         .write          = tracing_trace_options_write,
 };