From: Steven Rostedt (Red Hat) <rostedt@goodmis.org>
Date: Mon, 23 Nov 2015 22:35:24 +0000 (-0500)
Subject: ring-buffer: Put back the length if crossed page with add_timestamp
X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=bd1b7cd360f529394936f28746eb4aaa12d6770a;p=GitHub%2Fmoto-9609%2Fandroid_kernel_motorola_exynos9610.git

ring-buffer: Put back the length if crossed page with add_timestamp

Commit fcc742eaad7c "ring-buffer: Add event descriptor to simplify passing
data" added a descriptor that holds various data instead of passing around
several variables through parameters. The problem was that one of the
parameters was modified in a function and the code was designed not to have
an effect on that modified  parameter. Now that the parameter is a
descriptor and any modifications to it are non-volatile, the size of the
data could be unnecessarily expanded.

Remove the extra space added if a timestamp was added and the event went
across the page.

Cc: stable@vger.kernel.org # 4.3+
Fixes: fcc742eaad7c "ring-buffer: Add event descriptor to simplify passing data"
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 4dd6d5bc4e11..9c6045a27ba3 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -2797,8 +2797,11 @@ rb_reserve_next_event(struct ring_buffer *buffer,
 
 	event = __rb_reserve_next(cpu_buffer, &info);
 
-	if (unlikely(PTR_ERR(event) == -EAGAIN))
+	if (unlikely(PTR_ERR(event) == -EAGAIN)) {
+		if (info.add_timestamp)
+			info.length -= RB_LEN_TIME_EXTEND;
 		goto again;
+	}
 
 	if (!event)
 		goto out_fail;