[for-next][PATCH 2/7] ring-buffer: Put back the length if crossed page with add_timestamp

Steven Rostedt
2015-11-25T16:09:24Z

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From: "Steven Rostedt (Red Hat)" <rostedt@goodmis.org>

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>
---
kernel/trace/ring_buffer.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)

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;
--
2.6.1