1 files changed, 30 insertions, 5 deletions

diff --git a/kernel/trace/trace_seq.c b/kernel/trace/trace_seq.c
index 9c90b3a7dce2..32684ef4fb9d 100644
--- a/kernel/trace/trace_seq.c
+++ b/kernel/trace/trace_seq.c
@@ -13,12 +13,9 @@
  * trace_seq_init() more than once to reset the trace_seq to start
  * from scratch.
  * 
- * The buffer size is currently PAGE_SIZE, although it may become dynamic
- * in the future.
- *
  * A write to the buffer will either succeed or fail. That is, unlike
  * sprintf() there will not be a partial write (well it may write into
- * the buffer but it wont update the pointers). This allows users to
+ * the buffer but it won't update the pointers). This allows users to
  * try to write something into the trace_seq buffer and if it fails
  * they can flush it and try again.
  *
@@ -131,6 +128,7 @@ EXPORT_SYMBOL_GPL(trace_seq_bitmask);
  * trace_seq_vprintf - sequence printing of trace information
  * @s: trace sequence descriptor
  * @fmt: printf format string
+ * @args: Arguments for the format string
  *
  * The tracer may use either sequence operations or its own
  * copy to user routines. To simplify formatting of a trace
@@ -369,8 +367,12 @@ EXPORT_SYMBOL_GPL(trace_seq_path);
  */
 int trace_seq_to_user(struct trace_seq *s, char __user *ubuf, int cnt)
 {
+	int ret;
 	__trace_seq_init(s);
-	return seq_buf_to_user(&s->seq, ubuf, cnt);
+	ret = seq_buf_to_user(&s->seq, ubuf, s->readpos, cnt);
+	if (ret > 0)
+		s->readpos += ret;
+	return ret;
 }
 EXPORT_SYMBOL_GPL(trace_seq_to_user);
 
@@ -403,3 +405,26 @@ int trace_seq_hex_dump(struct trace_seq *s, const char *prefix_str,
 	return 1;
 }
 EXPORT_SYMBOL(trace_seq_hex_dump);
+
+/*
+ * trace_seq_acquire - acquire seq buffer with size len
+ * @s: trace sequence descriptor
+ * @len: size of buffer to be acquired
+ *
+ * acquire buffer with size of @len from trace_seq for output usage,
+ * user can fill string into that buffer.
+ *
+ * Returns start address of acquired buffer.
+ *
+ * it allow multiple usage in one trace output function call.
+ */
+char *trace_seq_acquire(struct trace_seq *s, unsigned int len)
+{
+	char *ret = trace_seq_buffer_ptr(s);
+
+	if (!WARN_ON_ONCE(seq_buf_buffer_left(&s->seq) < len))
+		seq_buf_commit(&s->seq, len);
+
+	return ret;
+}
+EXPORT_SYMBOL(trace_seq_acquire);