[PATCH v4 0/9] ring-buffer: Fixes for subbuf resizing and persistent buffers

This series addresses multiple issues discovered with the dynamic ring
buffer resizing.

Changelog:

v4:

  - Add rb_subbuf_start() helper (Steven)
  - kerneldoc additions
  - Fix races in trace_pipe_raw readers
  - Use rb_subbuf_capacity() in ring_buffer_subbuf_order_set()
  - use rb_page_capacity() in ring_buffer_map_get_reader (Sashiko)
  - Fix 32-bit overflow in ring_buffer_subbuf_order_set() (Sashiko)
  - Hold cpu_buffer::lock when modifying cpu_buffer->free_page in
    ring_buffer_subbuf_order_set (Sashiko)

v3 (https://lore.kernel.org/all/20260810125633.3344684-1-vdonnefort@google.com/ (local)):

  - Drop first 3 patches (Rebased on 7.2-rc7)
  - Add a patch to align "nr_pages" to unsigned int
  - Add a patch to remove useless trace_buffer::cpus
  - Add unsigned long cast for rb_subbuf_size()
  - subbuf_order fix for rb_free_cpu_buffer() (Sashiko)
  - Use __always_inline just like the other accessors for the hot-path.

v2 (https://lore.kernel.org/all/20260806211306.3704194-1-vdonnefort@google.com/ (local)):

  - Prevent resizing of the persistent ring buffer
  - Add missing bpage::order init
  - Rework subbuf_size/subbuf_order (Sashiko)
  - Remove ring_buffer_per_cpu::mapped
  - Dynamically calculate trace_buffer::max_data_size

v1 (https://lore.kernel.org/all/20260805153225.2096152-1-vdonnefort@google.com/ (local))

Vincent Donnefort (9):
  ring-buffer: Free cpu_buffer->free_page with subbuf_order
  ring-buffer: Hold cpu_buffer::lock when resizing a subbuf
  ring-buffer: Fix subbuf resize race with ring buffer readers
  ring-buffer: Fix subbuf resize race in ring_buffer_alloc_read_page()
  tracing: Fix subbuf resize races in trace_pipe_raw readers
  ring-buffer: Dynamically calculate max_data_size
  ring-buffer: Remove trace_buffer::cpus
  ring-buffer: Remove ring_buffer_per_cpu::mapped
  ring-buffer: Make nr_pages unsigned int

 include/linux/ring_buffer.h          |   4 +-
 kernel/trace/ring_buffer.c           | 354 +++++++++++++++++----------
 kernel/trace/ring_buffer_benchmark.c |   2 +-
 kernel/trace/trace.c                 |  92 +++----
 kernel/trace/trace.h                 |   1 -
 5 files changed, 269 insertions(+), 184 deletions(-)


base-commit: db2ddb87143519e20a95aa36c60b36107b736a58
-- 
2.55.0.691.gc56d675ccc-goog