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

Pull MD updates from Song:

"- Remove uses of bdevname, by Christoph Hellwig;
 - Bug fixes by Guoqing Jiang, and Xiao Ni."

* 'md-next' of https://git.kernel.org/pub/scm/linux/kernel/git/song/md:
  md: fix double free of io_acct_set bioset
  md: Don't set mddev private to NULL in raid0 pers->free
  md: remove most calls to bdevname
  md: protect md_unregister_thread from reentrancy
  md: don't unregister sync_thread with reconfig_mutex held