Merge branch 'for-6.15/io_uring' into for-6.15/io_uring-reg-vec

* for-6.15/io_uring: (80 commits)
  io_uring: introduce io_cache_free() helper
  io_uring/rsrc: skip NULL file/buffer checks in io_free_rsrc_node()
  io_uring/rsrc: avoid NULL node check on io_sqe_buffer_register() failure
  io_uring/rsrc: call io_free_node() on io_sqe_buffer_register() failure
  io_uring/rsrc: free io_rsrc_node using kfree()
  io_uring/rsrc: split out io_free_node() helper
  io_uring/rsrc: include io_uring_types.h in rsrc.h
  ublk: don't cast registered buffer index to int
  io_uring/nop: use io_find_buf_node()
  io_uring/rsrc: declare io_find_buf_node() in header file
  io_uring/ublk: report error when unregister operation fails
  io_uring: convert cmd_to_io_kiocb() macro to function
  io_uring/uring_cmd: specify io_uring_cmd_import_fixed() pointer type
  io_uring/rsrc: use rq_data_dir() to compute bvec dir
  selftests: ublk: add ublk zero copy test
  selftests: ublk: add file backed ublk
  selftests: ublk: add kernel selftests for ublk
  io_uring: cache nodes and mapped buffers
  ublk: zc register/unregister bvec
  io_uring: add support for kernel registered bvecs
  ...