1 files changed, 11 insertions, 7 deletions

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 91874a95060d..9ab18995ff1e 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -280,6 +280,8 @@ EXPORT_SYMBOL_GPL(ring_buffer_event_data);
 /* Missed count stored at end */
 #define RB_MISSED_STORED        (1 << 30)
 
+#define RB_MISSED_FLAGS         (RB_MISSED_EVENTS|RB_MISSED_STORED)
+
 struct buffer_data_page {
         u64              time_stamp;    /* page time stamp */
         local_t          commit;        /* write committed index */
@@ -331,7 +333,9 @@ static void rb_init_page(struct buffer_data_page *bpage)
  */
 size_t ring_buffer_page_len(void *page)
 {
-        return local_read(&((struct buffer_data_page *)page)->commit)
+        struct buffer_data_page *bpage = page;
+
+        return (local_read(&bpage->commit) & ~RB_MISSED_FLAGS)
                 + BUF_PAGE_HDR_SIZE;
 }
 
@@ -1799,12 +1803,6 @@ void ring_buffer_change_overwrite(struct ring_buffer *buffer, int val)
 }
 EXPORT_SYMBOL_GPL(ring_buffer_change_overwrite);
 
-static __always_inline void *
-__rb_data_page_index(struct buffer_data_page *bpage, unsigned index)
-{
-        return bpage->data + index;
-}
-
 static __always_inline void *__rb_page_index(struct buffer_page *bpage, unsigned index)
 {
         return bpage->page->data + index;
@@ -4406,8 +4404,13 @@ void ring_buffer_free_read_page(struct ring_buffer *buffer, int cpu, void *data)
 {
         struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
         struct buffer_data_page *bpage = data;
+        struct page *page = virt_to_page(bpage);
         unsigned long flags;
 
+        /* If the page is still in use someplace else, we can't reuse it */
+        if (page_ref_count(page) > 1)
+                goto out;
+
         local_irq_save(flags);
         arch_spin_lock(&cpu_buffer->lock);
 
@@ -4419,6 +4422,7 @@ void ring_buffer_free_read_page(struct ring_buffer *buffer, int cpu, void *data)
         arch_spin_unlock(&cpu_buffer->lock);
         local_irq_restore(flags);
 
+ out:
         free_page((unsigned long)bpage);
 }
 EXPORT_SYMBOL_GPL(ring_buffer_free_read_page);