1 files changed, 13 insertions, 26 deletions

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index c792ea893b01..342eacc4baa8 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -321,9 +321,10 @@ struct buffer_data_page {
 };
 
 struct buffer_page {
+        struct list_head list;          /* list of buffer pages */
         local_t          write;         /* index for next write */
         unsigned         read;          /* index for next read */
-        struct list_head list;          /* list of free pages */
+        local_t          entries;       /* entries on this page */
         struct buffer_data_page *page;  /* Actual data page */
 };
 
@@ -977,30 +978,6 @@ static inline unsigned rb_head_size(struct ring_buffer_per_cpu *cpu_buffer)
         return rb_page_commit(cpu_buffer->head_page);
 }
 
-/*
- * When the tail hits the head and the buffer is in overwrite mode,
- * the head jumps to the next page and all content on the previous
- * page is discarded. But before doing so, we update the overrun
- * variable of the buffer.
- */
-static void rb_update_overflow(struct ring_buffer_per_cpu *cpu_buffer)
-{
-        struct ring_buffer_event *event;
-        unsigned long head;
-
-        for (head = 0; head < rb_head_size(cpu_buffer);
-             head += rb_event_length(event)) {
-
-                event = __rb_page_index(cpu_buffer->head_page, head);
-                if (RB_WARN_ON(cpu_buffer, rb_null_event(event)))
-                        return;
-                /* Only count data entries */
-                if (event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
-                        continue;
-                cpu_buffer->overrun++;
-        }
-}
-
 static inline void rb_inc_page(struct ring_buffer_per_cpu *cpu_buffer,
                                struct buffer_page **bpage)
 {
@@ -1253,7 +1230,8 @@ __rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer,
                         /* tail_page has not moved yet? */
                         if (tail_page == cpu_buffer->tail_page) {
                                 /* count overflows */
-                                rb_update_overflow(cpu_buffer);
+                                cpu_buffer->overrun +=
+                                        local_read(&head_page->entries);
 
                                 rb_inc_page(cpu_buffer, &head_page);
                                 cpu_buffer->head_page = head_page;
@@ -1268,6 +1246,7 @@ __rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer,
                  */
                 if (tail_page == cpu_buffer->tail_page) {
                         local_set(&next_page->write, 0);
+                        local_set(&next_page->entries, 0);
                         local_set(&next_page->page->commit, 0);
                         cpu_buffer->tail_page = next_page;
 
@@ -1313,6 +1292,10 @@ __rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer,
         event = __rb_page_index(tail_page, tail);
         rb_update_event(event, type, length);
 
+        /* The passed in type is zero for DATA */
+        if (likely(!type))
+                local_inc(&tail_page->entries);
+
         /*
          * If this is a commit and the tail is zero, then update
          * this page's time stamp.
@@ -2183,6 +2166,7 @@ rb_get_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
         cpu_buffer->reader_page->list.prev = reader->list.prev;
 
         local_set(&cpu_buffer->reader_page->write, 0);
+        local_set(&cpu_buffer->reader_page->entries, 0);
         local_set(&cpu_buffer->reader_page->page->commit, 0);
 
         /* Make the reader page now replace the head */
@@ -2629,6 +2613,7 @@ rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer)
         cpu_buffer->head_page
                 = list_entry(cpu_buffer->pages.next, struct buffer_page, list);
         local_set(&cpu_buffer->head_page->write, 0);
+        local_set(&cpu_buffer->head_page->entries, 0);
         local_set(&cpu_buffer->head_page->page->commit, 0);
 
         cpu_buffer->head_page->read = 0;
@@ -2638,6 +2623,7 @@ rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer)
 
         INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
         local_set(&cpu_buffer->reader_page->write, 0);
+        local_set(&cpu_buffer->reader_page->entries, 0);
         local_set(&cpu_buffer->reader_page->page->commit, 0);
         cpu_buffer->reader_page->read = 0;
 
@@ -2996,6 +2982,7 @@ int ring_buffer_read_page(struct ring_buffer *buffer,
                 bpage = reader->page;
                 reader->page = *data_page;
                 local_set(&reader->write, 0);
+                local_set(&reader->entries, 0);
                 reader->read = 0;
                 *data_page = bpage;