1 files changed, 221 insertions, 177 deletions

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index bca96377fd4e..b0c7aa407943 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -5,7 +5,6 @@
  */
 #include <linux/ring_buffer.h>
 #include <linux/trace_clock.h>
-#include <linux/ftrace_irq.h>
 #include <linux/spinlock.h>
 #include <linux/debugfs.h>
 #include <linux/uaccess.h>
@@ -224,6 +223,9 @@ enum {
         RB_LEN_TIME_STAMP = 16,
 };
 
+#define skip_time_extend(event) \
+        ((struct ring_buffer_event *)((char *)event + RB_LEN_TIME_EXTEND))
+
 static inline int rb_null_event(struct ring_buffer_event *event)
 {
         return event->type_len == RINGBUF_TYPE_PADDING && !event->time_delta;
@@ -248,8 +250,12 @@ rb_event_data_length(struct ring_buffer_event *event)
         return length + RB_EVNT_HDR_SIZE;
 }
 
-/* inline for ring buffer fast paths */
-static unsigned
+/*
+ * Return the length of the given event. Will return
+ * the length of the time extend if the event is a
+ * time extend.
+ */
+static inline unsigned
 rb_event_length(struct ring_buffer_event *event)
 {
         switch (event->type_len) {
@@ -274,13 +280,41 @@ rb_event_length(struct ring_buffer_event *event)
         return 0;
 }
 
+/*
+ * Return total length of time extend and data,
+ *   or just the event length for all other events.
+ */
+static inline unsigned
+rb_event_ts_length(struct ring_buffer_event *event)
+{
+        unsigned len = 0;
+
+        if (event->type_len == RINGBUF_TYPE_TIME_EXTEND) {
+                /* time extends include the data event after it */
+                len = RB_LEN_TIME_EXTEND;
+                event = skip_time_extend(event);
+        }
+        return len + rb_event_length(event);
+}
+
 /**
  * ring_buffer_event_length - return the length of the event
  * @event: the event to get the length of
+ *
+ * Returns the size of the data load of a data event.
+ * If the event is something other than a data event, it
+ * returns the size of the event itself. With the exception
+ * of a TIME EXTEND, where it still returns the size of the
+ * data load of the data event after it.
  */
 unsigned ring_buffer_event_length(struct ring_buffer_event *event)
 {
-        unsigned length = rb_event_length(event);
+        unsigned length;
+
+        if (event->type_len == RINGBUF_TYPE_TIME_EXTEND)
+                event = skip_time_extend(event);
+
+        length = rb_event_length(event);
         if (event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
                 return length;
         length -= RB_EVNT_HDR_SIZE;
@@ -294,6 +328,8 @@ EXPORT_SYMBOL_GPL(ring_buffer_event_length);
 static void *
 rb_event_data(struct ring_buffer_event *event)
 {
+        if (event->type_len == RINGBUF_TYPE_TIME_EXTEND)
+                event = skip_time_extend(event);
         BUG_ON(event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX);
         /* If length is in len field, then array[0] has the data */
         if (event->type_len)
@@ -404,9 +440,6 @@ static inline int test_time_stamp(u64 delta)
 /* Max payload is BUF_PAGE_SIZE - header (8bytes) */
 #define BUF_MAX_DATA_SIZE (BUF_PAGE_SIZE - (sizeof(u32) * 2))
 
-/* Max number of timestamps that can fit on a page */
-#define RB_TIMESTAMPS_PER_PAGE  (BUF_PAGE_SIZE / RB_LEN_TIME_EXTEND)
-
 int ring_buffer_print_page_header(struct trace_seq *s)
 {
         struct buffer_data_page field;
@@ -635,7 +668,7 @@ static struct list_head *rb_list_head(struct list_head *list)
  * the reader page). But if the next page is a header page,
  * its flags will be non zero.
  */
-static int inline
+static inline int
 rb_is_head_page(struct ring_buffer_per_cpu *cpu_buffer,
                 struct buffer_page *page, struct list_head *list)
 {
@@ -1395,6 +1428,17 @@ int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size)
 }
 EXPORT_SYMBOL_GPL(ring_buffer_resize);
 
+void ring_buffer_change_overwrite(struct ring_buffer *buffer, int val)
+{
+        mutex_lock(&buffer->mutex);
+        if (val)
+                buffer->flags |= RB_FL_OVERWRITE;
+        else
+                buffer->flags &= ~RB_FL_OVERWRITE;
+        mutex_unlock(&buffer->mutex);
+}
+EXPORT_SYMBOL_GPL(ring_buffer_change_overwrite);
+
 static inline void *
 __rb_data_page_index(struct buffer_data_page *bpage, unsigned index)
 {
@@ -1434,7 +1478,7 @@ static inline unsigned long rb_page_entries(struct buffer_page *bpage)
         return local_read(&bpage->entries) & RB_WRITE_MASK;
 }
 
-/* Size is determined by what has been commited */
+/* Size is determined by what has been committed */
 static inline unsigned rb_page_size(struct buffer_page *bpage)
 {
         return rb_page_commit(bpage);
@@ -1546,6 +1590,25 @@ static void rb_inc_iter(struct ring_buffer_iter *iter)
         iter->head = 0;
 }
 
+/* Slow path, do not inline */
+static noinline struct ring_buffer_event *
+rb_add_time_stamp(struct ring_buffer_event *event, u64 delta)
+{
+        event->type_len = RINGBUF_TYPE_TIME_EXTEND;
+
+        /* Not the first event on the page? */
+        if (rb_event_index(event)) {
+                event->time_delta = delta & TS_MASK;
+                event->array[0] = delta >> TS_SHIFT;
+        } else {
+                /* nope, just zero it */
+                event->time_delta = 0;
+                event->array[0] = 0;
+        }
+
+        return skip_time_extend(event);
+}
+
 /**
  * ring_buffer_update_event - update event type and data
  * @event: the even to update
@@ -1558,28 +1621,31 @@ static void rb_inc_iter(struct ring_buffer_iter *iter)
  * data field.
  */
 static void
-rb_update_event(struct ring_buffer_event *event,
-                         unsigned type, unsigned length)
+rb_update_event(struct ring_buffer_per_cpu *cpu_buffer,
+                struct ring_buffer_event *event, unsigned length,
+                int add_timestamp, u64 delta)
 {
-        event->type_len = type;
-
-        switch (type) {
-
-        case RINGBUF_TYPE_PADDING:
-        case RINGBUF_TYPE_TIME_EXTEND:
-        case RINGBUF_TYPE_TIME_STAMP:
-                break;
+        /* Only a commit updates the timestamp */
+        if (unlikely(!rb_event_is_commit(cpu_buffer, event)))
+                delta = 0;
 
-        case 0:
-                length -= RB_EVNT_HDR_SIZE;
-                if (length > RB_MAX_SMALL_DATA || RB_FORCE_8BYTE_ALIGNMENT)
-                        event->array[0] = length;
-                else
-                        event->type_len = DIV_ROUND_UP(length, RB_ALIGNMENT);
-                break;
-        default:
-                BUG();
+        /*
+         * If we need to add a timestamp, then we
+         * add it to the start of the resevered space.
+         */
+        if (unlikely(add_timestamp)) {
+                event = rb_add_time_stamp(event, delta);
+                length -= RB_LEN_TIME_EXTEND;
+                delta = 0;
         }
+
+        event->time_delta = delta;
+        length -= RB_EVNT_HDR_SIZE;
+        if (length > RB_MAX_SMALL_DATA || RB_FORCE_8BYTE_ALIGNMENT) {
+                event->type_len = 0;
+                event->array[0] = length;
+        } else
+                event->type_len = DIV_ROUND_UP(length, RB_ALIGNMENT);
 }
 
 /*
@@ -1823,10 +1889,13 @@ rb_reset_tail(struct ring_buffer_per_cpu *cpu_buffer,
         local_sub(length, &tail_page->write);
 }
 
-static struct ring_buffer_event *
+/*
+ * This is the slow path, force gcc not to inline it.
+ */
+static noinline struct ring_buffer_event *
 rb_move_tail(struct ring_buffer_per_cpu *cpu_buffer,
              unsigned long length, unsigned long tail,
-             struct buffer_page *tail_page, u64 *ts)
+             struct buffer_page *tail_page, u64 ts)
 {
         struct buffer_page *commit_page = cpu_buffer->commit_page;
         struct ring_buffer *buffer = cpu_buffer->buffer;
@@ -1909,8 +1978,8 @@ rb_move_tail(struct ring_buffer_per_cpu *cpu_buffer,
                  * Nested commits always have zero deltas, so
                  * just reread the time stamp
                  */
-                *ts = rb_time_stamp(buffer);
-                next_page->page->time_stamp = *ts;
+                ts = rb_time_stamp(buffer);
+                next_page->page->time_stamp = ts;
         }
 
  out_again:
@@ -1929,12 +1998,21 @@ rb_move_tail(struct ring_buffer_per_cpu *cpu_buffer,
 
 static struct ring_buffer_event *
 __rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer,
-                  unsigned type, unsigned long length, u64 *ts)
+                  unsigned long length, u64 ts,
+                  u64 delta, int add_timestamp)
 {
         struct buffer_page *tail_page;
         struct ring_buffer_event *event;
         unsigned long tail, write;
 
+        /*
+         * If the time delta since the last event is too big to
+         * hold in the time field of the event, then we append a
+         * TIME EXTEND event ahead of the data event.
+         */
+        if (unlikely(add_timestamp))
+                length += RB_LEN_TIME_EXTEND;
+
         tail_page = cpu_buffer->tail_page;
         write = local_add_return(length, &tail_page->write);
 
@@ -1943,7 +2021,7 @@ __rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer,
         tail = write - length;
 
         /* See if we shot pass the end of this buffer page */
-        if (write > BUF_PAGE_SIZE)
+        if (unlikely(write > BUF_PAGE_SIZE))
                 return rb_move_tail(cpu_buffer, length, tail,
                                     tail_page, ts);
 
@@ -1951,18 +2029,16 @@ __rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer,
 
         event = __rb_page_index(tail_page, tail);
         kmemcheck_annotate_bitfield(event, bitfield);
-        rb_update_event(event, type, length);
+        rb_update_event(cpu_buffer, event, length, add_timestamp, delta);
 
-        /* The passed in type is zero for DATA */
-        if (likely(!type))
-                local_inc(&tail_page->entries);
+        local_inc(&tail_page->entries);
 
         /*
          * If this is the first commit on the page, then update
          * its timestamp.
          */
         if (!tail)
-                tail_page->page->time_stamp = *ts;
+                tail_page->page->time_stamp = ts;
 
         return event;
 }
@@ -1977,7 +2053,7 @@ rb_try_to_discard(struct ring_buffer_per_cpu *cpu_buffer,
         unsigned long addr;
 
         new_index = rb_event_index(event);
-        old_index = new_index + rb_event_length(event);
+        old_index = new_index + rb_event_ts_length(event);
         addr = (unsigned long)event;
         addr &= PAGE_MASK;
 
@@ -2003,76 +2079,13 @@ rb_try_to_discard(struct ring_buffer_per_cpu *cpu_buffer,
         return 0;
 }
 
-static int
-rb_add_time_stamp(struct ring_buffer_per_cpu *cpu_buffer,
-                  u64 *ts, u64 *delta)
-{
-        struct ring_buffer_event *event;
-        int ret;
-
-        WARN_ONCE(*delta > (1ULL << 59),
-                  KERN_WARNING "Delta way too big! %llu ts=%llu write stamp = %llu\n",
-                  (unsigned long long)*delta,
-                  (unsigned long long)*ts,
-                  (unsigned long long)cpu_buffer->write_stamp);
-
-        /*
-         * The delta is too big, we to add a
-         * new timestamp.
-         */
-        event = __rb_reserve_next(cpu_buffer,
-                                  RINGBUF_TYPE_TIME_EXTEND,
-                                  RB_LEN_TIME_EXTEND,
-                                  ts);
-        if (!event)
-                return -EBUSY;
-
-        if (PTR_ERR(event) == -EAGAIN)
-                return -EAGAIN;
-
-        /* Only a commited time event can update the write stamp */
-        if (rb_event_is_commit(cpu_buffer, event)) {
-                /*
-                 * If this is the first on the page, then it was
-                 * updated with the page itself. Try to discard it
-                 * and if we can't just make it zero.
-                 */
-                if (rb_event_index(event)) {
-                        event->time_delta = *delta & TS_MASK;
-                        event->array[0] = *delta >> TS_SHIFT;
-                } else {
-                        /* try to discard, since we do not need this */
-                        if (!rb_try_to_discard(cpu_buffer, event)) {
-                                /* nope, just zero it */
-                                event->time_delta = 0;
-                                event->array[0] = 0;
-                        }
-                }
-                cpu_buffer->write_stamp = *ts;
-                /* let the caller know this was the commit */
-                ret = 1;
-        } else {
-                /* Try to discard the event */
-                if (!rb_try_to_discard(cpu_buffer, event)) {
-                        /* Darn, this is just wasted space */
-                        event->time_delta = 0;
-                        event->array[0] = 0;
-                }
-                ret = 0;
-        }
-
-        *delta = 0;
-
-        return ret;
-}
-
 static void rb_start_commit(struct ring_buffer_per_cpu *cpu_buffer)
 {
         local_inc(&cpu_buffer->committing);
         local_inc(&cpu_buffer->commits);
 }
 
-static void rb_end_commit(struct ring_buffer_per_cpu *cpu_buffer)
+static inline void rb_end_commit(struct ring_buffer_per_cpu *cpu_buffer)
 {
         unsigned long commits;
 
@@ -2110,9 +2123,10 @@ rb_reserve_next_event(struct ring_buffer *buffer,
                       unsigned long length)
 {
         struct ring_buffer_event *event;
-        u64 ts, delta = 0;
-        int commit = 0;
+        u64 ts, delta;
         int nr_loops = 0;
+        int add_timestamp;
+        u64 diff;
 
         rb_start_commit(cpu_buffer);
 
@@ -2133,6 +2147,9 @@ rb_reserve_next_event(struct ring_buffer *buffer,
 
         length = rb_calculate_event_length(length);
  again:
+        add_timestamp = 0;
+        delta = 0;
+
         /*
          * We allow for interrupts to reenter here and do a trace.
          * If one does, it will cause this original code to loop
@@ -2146,56 +2163,40 @@ rb_reserve_next_event(struct ring_buffer *buffer,
                 goto out_fail;
 
         ts = rb_time_stamp(cpu_buffer->buffer);
+        diff = ts - cpu_buffer->write_stamp;
 
-        /*
-         * Only the first commit can update the timestamp.
-         * Yes there is a race here. If an interrupt comes in
-         * just after the conditional and it traces too, then it
-         * will also check the deltas. More than one timestamp may
-         * also be made. But only the entry that did the actual
-         * commit will be something other than zero.
-         */
-        if (likely(cpu_buffer->tail_page == cpu_buffer->commit_page &&
-                   rb_page_write(cpu_buffer->tail_page) ==
-                   rb_commit_index(cpu_buffer))) {
-                u64 diff;
-
-                diff = ts - cpu_buffer->write_stamp;
-
-                /* make sure this diff is calculated here */
-                barrier();
-
-                /* Did the write stamp get updated already? */
-                if (unlikely(ts < cpu_buffer->write_stamp))
-                        goto get_event;
+        /* make sure this diff is calculated here */
+        barrier();
 
+        /* Did the write stamp get updated already? */
+        if (likely(ts >= cpu_buffer->write_stamp)) {
                 delta = diff;
                 if (unlikely(test_time_stamp(delta))) {
-
-                        commit = rb_add_time_stamp(cpu_buffer, &ts, &delta);
-                        if (commit == -EBUSY)
-                                goto out_fail;
-
-                        if (commit == -EAGAIN)
-                                goto again;
-
-                        RB_WARN_ON(cpu_buffer, commit < 0);
+                        int local_clock_stable = 1;
+#ifdef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK
+                        local_clock_stable = sched_clock_stable;
+#endif
+                        WARN_ONCE(delta > (1ULL << 59),
+                                  KERN_WARNING "Delta way too big! %llu ts=%llu write stamp = %llu\n%s",
+                                  (unsigned long long)delta,
+                                  (unsigned long long)ts,
+                                  (unsigned long long)cpu_buffer->write_stamp,
+                                  local_clock_stable ? "" :
+                                  "If you just came from a suspend/resume,\n"
+                                  "please switch to the trace global clock:\n"
+                                  "  echo global > /sys/kernel/debug/tracing/trace_clock\n");
+                        add_timestamp = 1;
                 }
         }
 
- get_event:
-        event = __rb_reserve_next(cpu_buffer, 0, length, &ts);
+        event = __rb_reserve_next(cpu_buffer, length, ts,
+                                  delta, add_timestamp);
         if (unlikely(PTR_ERR(event) == -EAGAIN))
                 goto again;
 
         if (!event)
                 goto out_fail;
 
-        if (!rb_event_is_commit(cpu_buffer, event))
-                delta = 0;
-
-        event->time_delta = delta;
-
         return event;
 
  out_fail:
@@ -2207,32 +2208,39 @@ rb_reserve_next_event(struct ring_buffer *buffer,
 
 #define TRACE_RECURSIVE_DEPTH 16
 
-static int trace_recursive_lock(void)
+/* Keep this code out of the fast path cache */
+static noinline void trace_recursive_fail(void)
 {
-        current->trace_recursion++;
-
-        if (likely(current->trace_recursion < TRACE_RECURSIVE_DEPTH))
-                return 0;
-
         /* Disable all tracing before we do anything else */
         tracing_off_permanent();
 
         printk_once(KERN_WARNING "Tracing recursion: depth[%ld]:"
                     "HC[%lu]:SC[%lu]:NMI[%lu]\n",
-                    current->trace_recursion,
+                    trace_recursion_buffer(),
                     hardirq_count() >> HARDIRQ_SHIFT,
                     softirq_count() >> SOFTIRQ_SHIFT,
                     in_nmi());
 
         WARN_ON_ONCE(1);
+}
+
+static inline int trace_recursive_lock(void)
+{
+        trace_recursion_inc();
+
+        if (likely(trace_recursion_buffer() < TRACE_RECURSIVE_DEPTH))
+                return 0;
+
+        trace_recursive_fail();
+
         return -1;
 }
 
-static void trace_recursive_unlock(void)
+static inline void trace_recursive_unlock(void)
 {
-        WARN_ON_ONCE(!current->trace_recursion);
+        WARN_ON_ONCE(!trace_recursion_buffer());
 
-        current->trace_recursion--;
+        trace_recursion_dec();
 }
 
 #else
@@ -2308,12 +2316,28 @@ static void
 rb_update_write_stamp(struct ring_buffer_per_cpu *cpu_buffer,
                       struct ring_buffer_event *event)
 {
+        u64 delta;
+
         /*
          * The event first in the commit queue updates the
          * time stamp.
          */
-        if (rb_event_is_commit(cpu_buffer, event))
-                cpu_buffer->write_stamp += event->time_delta;
+        if (rb_event_is_commit(cpu_buffer, event)) {
+                /*
+                 * A commit event that is first on a page
+                 * updates the write timestamp with the page stamp
+                 */
+                if (!rb_event_index(event))
+                        cpu_buffer->write_stamp =
+                                cpu_buffer->commit_page->page->time_stamp;
+                else if (event->type_len == RINGBUF_TYPE_TIME_EXTEND) {
+                        delta = event->array[0];
+                        delta <<= TS_SHIFT;
+                        delta += event->time_delta;
+                        cpu_buffer->write_stamp += delta;
+                } else
+                        cpu_buffer->write_stamp += event->time_delta;
+        }
 }
 
 static void rb_commit(struct ring_buffer_per_cpu *cpu_buffer,
@@ -2353,6 +2377,9 @@ EXPORT_SYMBOL_GPL(ring_buffer_unlock_commit);
 
 static inline void rb_event_discard(struct ring_buffer_event *event)
 {
+        if (event->type_len == RINGBUF_TYPE_TIME_EXTEND)
+                event = skip_time_extend(event);
+
         /* array[0] holds the actual length for the discarded event */
         event->array[0] = rb_event_data_length(event) - RB_EVNT_HDR_SIZE;
         event->type_len = RINGBUF_TYPE_PADDING;
@@ -2606,6 +2633,19 @@ void ring_buffer_record_enable_cpu(struct ring_buffer *buffer, int cpu)
 }
 EXPORT_SYMBOL_GPL(ring_buffer_record_enable_cpu);
 
+/*
+ * The total entries in the ring buffer is the running counter
+ * of entries entered into the ring buffer, minus the sum of
+ * the entries read from the ring buffer and the number of
+ * entries that were overwritten.
+ */
+static inline unsigned long
+rb_num_of_entries(struct ring_buffer_per_cpu *cpu_buffer)
+{
+        return local_read(&cpu_buffer->entries) -
+                (local_read(&cpu_buffer->overrun) + cpu_buffer->read);
+}
+
 /**
  * ring_buffer_entries_cpu - get the number of entries in a cpu buffer
  * @buffer: The ring buffer
@@ -2614,16 +2654,13 @@ EXPORT_SYMBOL_GPL(ring_buffer_record_enable_cpu);
 unsigned long ring_buffer_entries_cpu(struct ring_buffer *buffer, int cpu)
 {
         struct ring_buffer_per_cpu *cpu_buffer;
-        unsigned long ret;
 
         if (!cpumask_test_cpu(cpu, buffer->cpumask))
                 return 0;
 
         cpu_buffer = buffer->buffers[cpu];
-        ret = (local_read(&cpu_buffer->entries) - local_read(&cpu_buffer->overrun))
-                - cpu_buffer->read;
 
-        return ret;
+        return rb_num_of_entries(cpu_buffer);
 }
 EXPORT_SYMBOL_GPL(ring_buffer_entries_cpu);
 
@@ -2684,8 +2721,7 @@ unsigned long ring_buffer_entries(struct ring_buffer *buffer)
         /* if you care about this being correct, lock the buffer */
         for_each_buffer_cpu(buffer, cpu) {
                 cpu_buffer = buffer->buffers[cpu];
-                entries += (local_read(&cpu_buffer->entries) -
-                            local_read(&cpu_buffer->overrun)) - cpu_buffer->read;
+                entries += rb_num_of_entries(cpu_buffer);
         }
 
         return entries;
@@ -2896,7 +2932,7 @@ rb_get_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
         /*
          * cpu_buffer->pages just needs to point to the buffer, it
          *  has no specific buffer page to point to. Lets move it out
-         *  of our way so we don't accidently swap it.
+         *  of our way so we don't accidentally swap it.
          */
         cpu_buffer->pages = reader->list.prev;
 
@@ -3040,12 +3076,12 @@ rb_buffer_peek(struct ring_buffer_per_cpu *cpu_buffer, u64 *ts,
 
  again:
         /*
-         * We repeat when a timestamp is encountered. It is possible
-         * to get multiple timestamps from an interrupt entering just
-         * as one timestamp is about to be written, or from discarded
-         * commits. The most that we can have is the number on a single page.
+         * We repeat when a time extend is encountered.
+         * Since the time extend is always attached to a data event,
+         * we should never loop more than once.
+         * (We never hit the following condition more than twice).
          */
-        if (RB_WARN_ON(cpu_buffer, ++nr_loops > RB_TIMESTAMPS_PER_PAGE))
+        if (RB_WARN_ON(cpu_buffer, ++nr_loops > 2))
                 return NULL;
 
         reader = rb_get_reader_page(cpu_buffer);
@@ -3121,14 +3157,12 @@ rb_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
                 return NULL;
 
         /*
-         * We repeat when a timestamp is encountered.
-         * We can get multiple timestamps by nested interrupts or also
-         * if filtering is on (discarding commits). Since discarding
-         * commits can be frequent we can get a lot of timestamps.
-         * But we limit them by not adding timestamps if they begin
-         * at the start of a page.
+         * We repeat when a time extend is encountered.
+         * Since the time extend is always attached to a data event,
+         * we should never loop more than once.
+         * (We never hit the following condition more than twice).
          */
-        if (RB_WARN_ON(cpu_buffer, ++nr_loops > RB_TIMESTAMPS_PER_PAGE))
+        if (RB_WARN_ON(cpu_buffer, ++nr_loops > 2))
                 return NULL;
 
         if (rb_per_cpu_empty(cpu_buffer))
@@ -3826,7 +3860,8 @@ int ring_buffer_read_page(struct ring_buffer *buffer,
                 if (len > (commit - read))
                         len = (commit - read);
 
-                size = rb_event_length(event);
+                /* Always keep the time extend and data together */
+                size = rb_event_ts_length(event);
 
                 if (len < size)
                         goto out_unlock;
@@ -3836,6 +3871,13 @@ int ring_buffer_read_page(struct ring_buffer *buffer,
 
                 /* Need to copy one event at a time */
                 do {
+                        /* We need the size of one event, because
+                         * rb_advance_reader only advances by one event,
+                         * whereas rb_event_ts_length may include the size of
+                         * one or two events.
+                         * We have already ensured there's enough space if this
+                         * is a time extend. */
+                        size = rb_event_length(event);
                         memcpy(bpage->data + pos, rpage->data + rpos, size);
 
                         len -= size;
@@ -3848,8 +3890,9 @@ int ring_buffer_read_page(struct ring_buffer *buffer,
                                 break;
 
                         event = rb_reader_event(cpu_buffer);
-                        size = rb_event_length(event);
-                } while (len > size);
+                        /* Always keep the time extend and data together */
+                        size = rb_event_ts_length(event);
+                } while (len >= size);
 
                 /* update bpage */
                 local_set(&bpage->commit, pos);
@@ -3965,6 +4008,7 @@ static const struct file_operations rb_simple_fops = {
         .open           = tracing_open_generic,
         .read           = rb_simple_read,
         .write          = rb_simple_write,
+        .llseek         = default_llseek,
 };