[PATCH v6 1/4] tracing: Reset last_boot_info if ring buffer is reset

[Masami Hiramatsu (Google)]

From: Masami Hiramatsu (Google) <mhira...@kernel.org>

Commit 32dc0042528d ("tracing: Reset last-boot buffers when reading
out all cpu buffers") resets the last_boot_info when user read out
all data via trace_pipe* files. But it is not reset when user
resets the buffer from other files. (e.g. write `trace` file)

Reset it when the corresponding ring buffer is reset too.

Fixes: 32dc0042528d ("tracing: Reset last-boot buffers when reading out all cpu 
buffers")
Signed-off-by: Masami Hiramatsu (Google) <mhira...@kernel.org>
---
 kernel/trace/trace.c |    7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 396d59202438..5c3e4a554143 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -4891,6 +4891,8 @@ static int tracing_single_release_tr(struct inode *inode, 
struct file *file)
        return single_release(inode, file);
 }
 
+static bool update_last_data_if_empty(struct trace_array *tr);
+
 static int tracing_open(struct inode *inode, struct file *file)
 {
        struct trace_array *tr = inode->i_private;
@@ -4915,6 +4917,8 @@ static int tracing_open(struct inode *inode, struct file 
*file)
                        tracing_reset_online_cpus(trace_buf);
                else
                        tracing_reset_cpu(trace_buf, cpu);
+
+               update_last_data_if_empty(tr);
        }
 
        if (file->f_mode & FMODE_READ) {
@@ -5981,6 +5985,7 @@ tracing_set_trace_read(struct file *filp, char __user 
*ubuf,
 int tracer_init(struct tracer *t, struct trace_array *tr)
 {
        tracing_reset_online_cpus(&tr->array_buffer);
+       update_last_data_if_empty(tr);
        return t->init(tr);
 }
 
@@ -7799,6 +7804,7 @@ int tracing_set_clock(struct trace_array *tr, const char 
*clockstr)
                ring_buffer_set_clock(tr->max_buffer.buffer, 
trace_clocks[i].func);
        tracing_reset_online_cpus(&tr->max_buffer);
 #endif
+       update_last_data_if_empty(tr);
 
        if (tr->scratch && !(tr->flags & TRACE_ARRAY_FL_LAST_BOOT)) {
                struct trace_scratch *tscratch = tr->scratch;
@@ -8036,6 +8042,7 @@ tracing_snapshot_write(struct file *filp, const char 
__user *ubuf, size_t cnt,
                                tracing_reset_online_cpus(&tr->max_buffer);
                        else
                                tracing_reset_cpu(&tr->max_buffer, 
iter->cpu_file);
+                       update_last_data_if_empty(tr);
                }
                break;
        }