ring-buffer: fix ring_buffer_read_page

The ring_buffer_read_page was broken if it were to only copy part
of the page. This patch fixes that up as well as adds a parameter
to allow a length field, in order to only copy part of the buffer page.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>

1 files changed, 5 insertions, 2 deletions

diff --git a/include/linux/ring_buffer.h b/include/linux/ring_buffer.h
index f5e793d69bd3..79fcbc4b09d6 100644
--- a/include/linux/ring_buffer.h
+++ b/include/linux/ring_buffer.h
@@ -121,6 +121,9 @@ unsigned long ring_buffer_overrun_cpu(struct ring_buffer *buffer, int cpu);
 u64 ring_buffer_time_stamp(int cpu);
 void ring_buffer_normalize_time_stamp(int cpu, u64 *ts);
 
+size_t ring_buffer_page_len(void *page);
+
+
 /*
  * The below functions are fine to use outside the tracing facility.
  */
@@ -138,8 +141,8 @@ static inline int tracing_is_on(void) { return 0; }
 
 void *ring_buffer_alloc_read_page(struct ring_buffer *buffer);
 void ring_buffer_free_read_page(struct ring_buffer *buffer, void *data);
-int ring_buffer_read_page(struct ring_buffer *buffer,
-                          void **data_page, int cpu, int full);
+int ring_buffer_read_page(struct ring_buffer *buffer, void **data_page,
+                          size_t len, int cpu, int full);
 
 enum ring_buffer_flags {
         RB_FL_OVERWRITE         = 1 << 0,