Merge branch 'for-5.1/md-post' of https://github.com/liu-song-6/linux into for-5.1/block-post

Pull MD fixes from Song.

* 'for-5.1/md-post' of https://github.com/liu-song-6/linux:
  md: Fix failed allocation of md_register_thread
  It's wrong to add len to sector_nr in raid10 reshape twice
  raid5: set write hint for PPL