1 files changed, 33 insertions, 8 deletions

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index a2d13e8c8fd8..8d981ababc45 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -1941,9 +1941,14 @@ int tracing_open_generic(struct inode *inode, struct file *filp)
 static int tracing_release(struct inode *inode, struct file *file)
 {
         struct seq_file *m = (struct seq_file *)file->private_data;
-        struct trace_iterator *iter = m->private;
+        struct trace_iterator *iter;
         int cpu;
 
+        if (!(file->f_mode & FMODE_READ))
+                return 0;
+
+        iter = m->private;
+
         mutex_lock(&trace_types_lock);
         for_each_tracing_cpu(cpu) {
                 if (iter->buffer_iter[cpu])
@@ -1969,12 +1974,24 @@ static int tracing_open(struct inode *inode, struct file *file)
         struct trace_iterator *iter;
         int ret = 0;
 
-        iter = __tracing_open(inode, file);
-        if (IS_ERR(iter))
-                ret = PTR_ERR(iter);
-        else if (trace_flags & TRACE_ITER_LATENCY_FMT)
-                iter->iter_flags |= TRACE_FILE_LAT_FMT;
+        /* If this file was open for write, then erase contents */
+        if ((file->f_mode & FMODE_WRITE) &&
+            !(file->f_flags & O_APPEND)) {
+                long cpu = (long) inode->i_private;
+
+                if (cpu == TRACE_PIPE_ALL_CPU)
+                        tracing_reset_online_cpus(&global_trace);
+                else
+                        tracing_reset(&global_trace, cpu);
+        }
 
+        if (file->f_mode & FMODE_READ) {
+                iter = __tracing_open(inode, file);
+                if (IS_ERR(iter))
+                        ret = PTR_ERR(iter);
+                else if (trace_flags & TRACE_ITER_LATENCY_FMT)
+                        iter->iter_flags |= TRACE_FILE_LAT_FMT;
+        }
         return ret;
 }
 
@@ -2049,9 +2066,17 @@ static int show_traces_open(struct inode *inode, struct file *file)
         return ret;
 }
 
+static ssize_t
+tracing_write_stub(struct file *filp, const char __user *ubuf,
+                   size_t count, loff_t *ppos)
+{
+        return count;
+}
+
 static const struct file_operations tracing_fops = {
         .open           = tracing_open,
         .read           = seq_read,
+        .write          = tracing_write_stub,
         .llseek         = seq_lseek,
         .release        = tracing_release,
 };
@@ -3576,7 +3601,7 @@ static void tracing_init_debugfs_percpu(long cpu)
                 pr_warning("Could not create debugfs 'trace_pipe' entry\n");
 
         /* per cpu trace */
-        entry = debugfs_create_file("trace", 0444, d_cpu,
+        entry = debugfs_create_file("trace", 0644, d_cpu,
                                 (void *) cpu, &tracing_fops);
         if (!entry)
                 pr_warning("Could not create debugfs 'trace' entry\n");
@@ -3890,7 +3915,7 @@ static __init int tracer_init_debugfs(void)
         if (!entry)
                 pr_warning("Could not create debugfs 'tracing_cpumask' entry\n");
 
-        entry = debugfs_create_file("trace", 0444, d_tracer,
+        entry = debugfs_create_file("trace", 0644, d_tracer,
                                  (void *) TRACE_PIPE_ALL_CPU, &tracing_fops);
         if (!entry)
                 pr_warning("Could not create debugfs 'trace' entry\n");