1 files changed, 36 insertions, 27 deletions

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index e206951603c1..8619c5345889 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -195,20 +195,24 @@ void *ring_buffer_event_data(struct ring_buffer_event *event)
 #define TS_MASK         ((1ULL << TS_SHIFT) - 1)
 #define TS_DELTA_TEST   (~TS_MASK)
 
-/*
- * This hack stolen from mm/slob.c.
- * We can store per page timing information in the page frame of the page.
- * Thanks to Peter Zijlstra for suggesting this idea.
- */
-struct buffer_page {
+struct buffer_data_page {
         u64              time_stamp;    /* page time stamp */
-        local_t          write;         /* index for next write */
         local_t          commit;        /* write commited index */
+        unsigned char    data[];        /* data of buffer page */
+};
+
+struct buffer_page {
+        local_t          write;         /* index for next write */
         unsigned         read;          /* index for next read */
         struct list_head list;          /* list of free pages */
-        void *page;                     /* Actual data page */
+        struct buffer_data_page *page;  /* Actual data page */
 };
 
+static void rb_init_page(struct buffer_data_page *page)
+{
+        local_set(&page->commit, 0);
+}
+
 /*
  * Also stolen from mm/slob.c. Thanks to Mathieu Desnoyers for pointing
  * this issue out.
@@ -230,7 +234,7 @@ static inline int test_time_stamp(u64 delta)
         return 0;
 }
 
-#define BUF_PAGE_SIZE PAGE_SIZE
+#define BUF_PAGE_SIZE (PAGE_SIZE - sizeof(struct buffer_data_page))
 
 /*
  * head_page == tail_page && head == tail then buffer is empty.
@@ -333,6 +337,7 @@ static int rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
                 if (!addr)
                         goto free_pages;
                 page->page = (void *)addr;
+                rb_init_page(page->page);
         }
 
         list_splice(&pages, head);
@@ -378,6 +383,7 @@ rb_allocate_cpu_buffer(struct ring_buffer *buffer, int cpu)
         if (!addr)
                 goto fail_free_reader;
         page->page = (void *)addr;
+        rb_init_page(page->page);
 
         INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
 
@@ -647,6 +653,7 @@ int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size)
                         if (!addr)
                                 goto free_pages;
                         page->page = (void *)addr;
+                        rb_init_page(page->page);
                 }
         }
 
@@ -682,7 +689,7 @@ static inline int rb_null_event(struct ring_buffer_event *event)
 
 static inline void *__rb_page_index(struct buffer_page *page, unsigned index)
 {
-        return page->page + index;
+        return page->page->data + index;
 }
 
 static inline struct ring_buffer_event *
@@ -712,7 +719,7 @@ static inline unsigned rb_page_write(struct buffer_page *bpage)
 
 static inline unsigned rb_page_commit(struct buffer_page *bpage)
 {
-        return local_read(&bpage->commit);
+        return local_read(&bpage->page->commit);
 }
 
 /* Size is determined by what has been commited */
@@ -804,14 +811,15 @@ rb_set_commit_event(struct ring_buffer_per_cpu *cpu_buffer,
                 if (RB_WARN_ON(cpu_buffer,
                           cpu_buffer->commit_page == cpu_buffer->tail_page))
                         return;
-                cpu_buffer->commit_page->commit =
+                cpu_buffer->commit_page->page->commit =
                         cpu_buffer->commit_page->write;
                 rb_inc_page(cpu_buffer, &cpu_buffer->commit_page);
-                cpu_buffer->write_stamp = cpu_buffer->commit_page->time_stamp;
+                cpu_buffer->write_stamp =
+                        cpu_buffer->commit_page->page->time_stamp;
         }
 
         /* Now set the commit to the event's index */
-        local_set(&cpu_buffer->commit_page->commit, index);
+        local_set(&cpu_buffer->commit_page->page->commit, index);
 }
 
 static inline void
@@ -826,16 +834,17 @@ rb_set_commit_to_write(struct ring_buffer_per_cpu *cpu_buffer)
          * assign the commit to the tail.
          */
         while (cpu_buffer->commit_page != cpu_buffer->tail_page) {
-                cpu_buffer->commit_page->commit =
+                cpu_buffer->commit_page->page->commit =
                         cpu_buffer->commit_page->write;
                 rb_inc_page(cpu_buffer, &cpu_buffer->commit_page);
-                cpu_buffer->write_stamp = cpu_buffer->commit_page->time_stamp;
+                cpu_buffer->write_stamp =
+                        cpu_buffer->commit_page->page->time_stamp;
                 /* add barrier to keep gcc from optimizing too much */
                 barrier();
         }
         while (rb_commit_index(cpu_buffer) !=
                rb_page_write(cpu_buffer->commit_page)) {
-                cpu_buffer->commit_page->commit =
+                cpu_buffer->commit_page->page->commit =
                         cpu_buffer->commit_page->write;
                 barrier();
         }
@@ -843,7 +852,7 @@ rb_set_commit_to_write(struct ring_buffer_per_cpu *cpu_buffer)
 
 static void rb_reset_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
 {
-        cpu_buffer->read_stamp = cpu_buffer->reader_page->time_stamp;
+        cpu_buffer->read_stamp = cpu_buffer->reader_page->page->time_stamp;
         cpu_buffer->reader_page->read = 0;
 }
 
@@ -862,7 +871,7 @@ static inline void rb_inc_iter(struct ring_buffer_iter *iter)
         else
                 rb_inc_page(cpu_buffer, &iter->head_page);
 
-        iter->read_stamp = iter->head_page->time_stamp;
+        iter->read_stamp = iter->head_page->page->time_stamp;
         iter->head = 0;
 }
 
@@ -998,12 +1007,12 @@ __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->commit, 0);
+                        local_set(&next_page->page->commit, 0);
                         cpu_buffer->tail_page = next_page;
 
                         /* reread the time stamp */
                         *ts = ring_buffer_time_stamp(cpu_buffer->cpu);
-                        cpu_buffer->tail_page->time_stamp = *ts;
+                        cpu_buffer->tail_page->page->time_stamp = *ts;
                 }
 
                 /*
@@ -1048,7 +1057,7 @@ __rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer,
          * this page's time stamp.
          */
         if (!tail && rb_is_commit(cpu_buffer, event))
-                cpu_buffer->commit_page->time_stamp = *ts;
+                cpu_buffer->commit_page->page->time_stamp = *ts;
 
         return event;
 
@@ -1099,7 +1108,7 @@ rb_add_time_stamp(struct ring_buffer_per_cpu *cpu_buffer,
                         event->time_delta = *delta & TS_MASK;
                         event->array[0] = *delta >> TS_SHIFT;
                 } else {
-                        cpu_buffer->commit_page->time_stamp = *ts;
+                        cpu_buffer->commit_page->page->time_stamp = *ts;
                         event->time_delta = 0;
                         event->array[0] = 0;
                 }
@@ -1552,7 +1561,7 @@ static void rb_iter_reset(struct ring_buffer_iter *iter)
         if (iter->head)
                 iter->read_stamp = cpu_buffer->read_stamp;
         else
-                iter->read_stamp = iter->head_page->time_stamp;
+                iter->read_stamp = iter->head_page->page->time_stamp;
 }
 
 /**
@@ -1696,7 +1705,7 @@ 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->commit, 0);
+        local_set(&cpu_buffer->reader_page->page->commit, 0);
 
         /* Make the reader page now replace the head */
         reader->list.prev->next = &cpu_buffer->reader_page->list;
@@ -2088,7 +2097,7 @@ 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->commit, 0);
+        local_set(&cpu_buffer->head_page->page->commit, 0);
 
         cpu_buffer->head_page->read = 0;
 
@@ -2097,7 +2106,7 @@ 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->commit, 0);
+        local_set(&cpu_buffer->reader_page->page->commit, 0);
         cpu_buffer->reader_page->read = 0;
 
         cpu_buffer->overrun = 0;