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

Pull MD updates from Song:

"The major changes are:

  1. Performance improvement for raid10 discard requests, from Xiao Ni.
  2. Fix missing information of /proc/mdstat, from Jan Glauber."

* 'md-next' of https://git.kernel.org/pub/scm/linux/kernel/git/song/md:
  md: Fix missing unused status line of /proc/mdstat
  md/raid10: improve discard request for far layout
  md/raid10: improve raid10 discard request
  md/raid10: pull the code that wait for blocked dev into one function
  md/raid10: extend r10bio devs to raid disks
  md: add md_submit_discard_bio() for submitting discard bio