ring-buffer: Making persistent ring buffers robust

This is to make the persistent ring buffer more robust when sub-buffers are detected to be corrupted. Instead of invalidating the entire buffer, just invalidate the individual sub-buffers.

I started with Masami's patches and modified some from Sashiko reviews. I added a few patches to display the dropped events when the persistent ring buffers validation checks found sub-buffers were dropped due to being corrupted data.

Changes since v20: https://lore.kernel.org/all/[email protected]/

- squashed the fix for max_loops in rb_iter_peek()

- Still process reader page if head page fails validation (Sashiko)

- Removed left over printk() (Masami Hiramatsu)

Masami Hiramatsu (Google) (6):
ring-buffer: Skip invalid sub-buffers when validating persistent ring buffer
ring-buffer: Skip invalid sub-buffers when rewinding persistent ring buffer
ring-buffer: Add persistent ring buffer invalid-page inject test
ring-buffer: Show commit numbers in buffer_meta file
ring-buffer: Cleanup persistent ring buffer validation
ring-buffer: Cleanup buffer_data_page related code

Steven Rostedt (3):
ring-buffer: Have dropped subbuffers be persistent across reboots
ring-buffer: Show persistent buffer dropped events in trace file
ring-buffer: Show persistent buffer dropped events in trace_pipe file

----

 include/linux/ring_buffer.h |   1 +
 kernel/trace/Kconfig        |  34 +++
 kernel/trace/ring_buffer.c  | 543 +++++++++++++++++++++++++++++---------------
 kernel/trace/trace.c        |   4 +
 4 files changed, 402 insertions(+), 180 deletions(-)