[PATCH v4 2/3] ring-buffer: Handle RB_MISSED_* flags on commit field correctly

[Masami Hiramatsu (Google)]

From: Masami Hiramatsu (Google) <mhira...@kernel.org>

Since the MSBs of rb_data_page::commit are used for storing
RB_MISSED_EVENTS and RB_MISSED_STORED, we need to mask out those bits
when it is used for finding the size of data pages.

Fixes: 5f3b6e839f3c ("ring-buffer: Validate boot range memory events")
Fixes: 5b7be9c709e1 ("ring-buffer: Add test to validate the time stamp deltas")
Cc: sta...@vger.kernel.org
Signed-off-by: Masami Hiramatsu (Google) <mhira...@kernel.org>
---
 Changes in v4:
   - Fix to move rb_commit_index() after ring_buffer_per_cpu definition.
---
 kernel/trace/ring_buffer.c |   32 ++++++++++++++++----------------
 1 file changed, 16 insertions(+), 16 deletions(-)

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 3eb124c93d72..67bc652ba02a 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -395,6 +395,12 @@ static __always_inline unsigned int rb_page_commit(struct 
buffer_page *bpage)
        return local_read(&bpage->page->commit);
 }
 
+/* Size is determined by what has been committed */
+static __always_inline unsigned rb_page_size(struct buffer_page *bpage)
+{
+       return rb_page_commit(bpage) & ~RB_MISSED_MASK;
+}
+
 static void free_buffer_page(struct buffer_page *bpage)
 {
        /* Range pages are not to be freed */
@@ -614,6 +620,12 @@ struct ring_buffer_iter {
        int                             missed_events;
 };
 
+static __always_inline unsigned
+rb_commit_index(struct ring_buffer_per_cpu *cpu_buffer)
+{
+       return rb_page_commit(cpu_buffer->commit_page);
+}
+
 int ring_buffer_print_page_header(struct trace_buffer *buffer, struct 
trace_seq *s)
 {
        struct buffer_data_page field;
@@ -1907,7 +1919,7 @@ static int rb_validate_buffer(struct buffer_data_page 
*dpage, int cpu)
        u64 delta;
        int tail;
 
-       tail = local_read(&dpage->commit);
+       tail = local_read(&dpage->commit) & ~RB_MISSED_MASK;
        return rb_read_data_buffer(dpage, tail, cpu, &ts, &delta);
 }
 
@@ -1934,7 +1946,7 @@ static void rb_meta_validate_events(struct 
ring_buffer_per_cpu *cpu_buffer)
                goto invalid;
        }
        entries += ret;
-       entry_bytes += local_read(&cpu_buffer->reader_page->page->commit);
+       entry_bytes += rb_page_size(cpu_buffer->reader_page);
        local_set(&cpu_buffer->reader_page->entries, ret);
 
        ts = head_page->page->time_stamp;
@@ -2054,7 +2066,7 @@ static void rb_meta_validate_events(struct 
ring_buffer_per_cpu *cpu_buffer)
                        local_inc(&cpu_buffer->pages_touched);
 
                entries += ret;
-               entry_bytes += local_read(&head_page->page->commit);
+               entry_bytes += rb_page_size(head_page);
                local_set(&cpu_buffer->head_page->entries, ret);
 
                if (head_page == cpu_buffer->commit_page)
@@ -3257,18 +3269,6 @@ rb_iter_head_event(struct ring_buffer_iter *iter)
        return NULL;
 }
 
-/* Size is determined by what has been committed */
-static __always_inline unsigned rb_page_size(struct buffer_page *bpage)
-{
-       return rb_page_commit(bpage) & ~RB_MISSED_MASK;
-}
-
-static __always_inline unsigned
-rb_commit_index(struct ring_buffer_per_cpu *cpu_buffer)
-{
-       return rb_page_commit(cpu_buffer->commit_page);
-}
-
 static __always_inline unsigned
 rb_event_index(struct ring_buffer_per_cpu *cpu_buffer, struct 
ring_buffer_event *event)
 {
@@ -4433,7 +4433,7 @@ static void check_buffer(struct ring_buffer_per_cpu 
*cpu_buffer,
 
        if (tail == CHECK_FULL_PAGE) {
                full = true;
-               tail = local_read(&bpage->commit);
+               tail = local_read(&bpage->commit) & ~RB_MISSED_MASK;
        } else if (info->add_timestamp &
                   (RB_ADD_STAMP_FORCE | RB_ADD_STAMP_ABSOLUTE)) {
                /* Ignore events with absolute time stamps */