Merge tag 'md-next-20230817' of https://git.kernel.org/pub/scm/linux/kernel/git/song...

Pull MD changes from Song:

"1. Fix perf regression for raid0 large sequential writes, by Jan Kara.
 2. Fix split bio iostat for raid0, by David Jeffery.
 3. Various raid1 fixes, by Heinz Mauelshagen and Xueshi Hu."

* tag 'md-next-20230817' of https://git.kernel.org/pub/scm/linux/kernel/git/song/md:
  md: raid0: account for split bio in iostat accounting
  md/raid0: Fix performance regression for large sequential writes
  md/raid0: Factor out helper for mapping and submitting a bio
  md raid1: allow writebehind to work on any leg device set WriteMostly
  md/raid1: hold the barrier until handle_read_error() finishes
  md/raid1: free the r1bio before waiting for blocked rdev
  md/raid1: call free_r1bio() before allow_barrier() in raid_end_bio_io()