[PATCH 2/4] [PATCH 2/4] tracing: fix trace_seq_printf return value

[Steven Rostedt]

From: Jiri Olsa <jolsa@xxxxxxxxxx>

trace_seq_printf return value is a little ambiguous. It currently
returns the length of the space available in the buffer. printf
usually returns the amount written. This is not adequate here, because

  trace_seq_printf(s, "");

is perfectly legal, and returning 0 would indicate that it failed.

We can always see the amount written by looking at the before and after
values of s->len. This is not quite the same use as printf. We only care
if the string was successfully written to the buffer or not.

Making trace_seq_printf return 0 if the trace oversizes the buffer's free
space, 1 otherwise.

Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx>
LKML-Reference: <20091022120958.GB2311@xxxxxxxxxxxxxxxx>
Signed-off-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
---
 kernel/trace/trace_output.c |    5 ++++-
 1 files changed, 4 insertions(+), 1 deletions(-)

diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c
index ed17565..b6c12c6 100644
--- a/kernel/trace/trace_output.c
+++ b/kernel/trace/trace_output.c
@@ -69,6 +69,9 @@ enum print_line_t trace_print_printk_msg_only(struct trace_iterator *iter)
  * @s: trace sequence descriptor
  * @fmt: printf format string
  *
+ * It returns 0 if the trace oversizes the buffer's free
+ * space, 1 otherwise.
+ *
  * The tracer may use either sequence operations or its own
  * copy to user routines. To simplify formating of a trace
  * trace_seq_printf is used to store strings into a special
@@ -95,7 +98,7 @@ trace_seq_printf(struct trace_seq *s, const char *fmt, ...)
 
 	s->len += ret;
 
-	return len;
+	return 1;
 }
 EXPORT_SYMBOL_GPL(trace_seq_printf);
 
-- 
1.6.3.3


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