[PATCH 6.18 698/752] tracing: Reset last_boot_info if ring buffer is reset

Sasha Levin
2026-02-28T17:58:32Z

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

[ Upstream commit 804c4a2209bcf6ed4c45386f033e4d0f7c5bfda5 ]

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.

Cc: stable@vger.kernel.org
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Link: https://patch.msgid.link/177071302364.2293046.17895165659153977720.stgit@mhiramat.tok.corp.google.com
Fixes: 32dc0042528d ("tracing: Reset last-boot buffers when reading out all cpu buffers")
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
kernel/trace/trace.c | 6 ++++++
1 file changed, 6 insertions(+)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index e1d902464e080..d2eabc162205c 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -4852,6 +4852,8 @@ 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;
@@ -4876,6 +4878,8 @@ 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) {
@@ -5917,6 +5921,7 @@ 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);
}

@@ -7582,6 +7587,7 @@ 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;
--
2.51.0