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

Pull MD fixes from Song.

* 'md-next' of https://git.kernel.org/pub/scm/linux/kernel/git/song/md:
  md/raid1: stop mdx_raid1 thread when raid1 array run failed
  md/raid5: use bdev_write_cache instead of open coding it
  md: fix a crash in mempool_free
  md/raid0, raid10: Don't set discard sectors for request queue
  md/bitmap: Fix bitmap chunk size overflow issues
  md: introduce md_ro_state
  md: factor out __md_set_array_info()
  lib/raid6: drop RAID6_USE_EMPTY_ZERO_PAGE
  raid5-cache: use try_cmpxchg in r5l_wake_reclaim
  drivers/md/md-bitmap: check the return value of md_bitmap_get_counter()