Merge branch 'for-linus' of git://neil.brown.name/md

Merge branch 'for-linus' of git://neil.brown.name/md

* 'for-linus' of git://neil.brown.name/md:
  md: tidy up device searches in read_balance.
  md/raid1: fix some typos in comments.
  md/raid1: discard unused variable.
  md: unplug writes to external bitmaps.
  md: use separate bio pool for each md device.
  md: change type of first arg to sync_page_io.
  md/raid1: perform mem allocation before disabling writes during resync.
  md: use bio_kmalloc rather than bio_alloc when failure is acceptable.
  md: Fix possible deadlock with multiple mempool allocations.
  md: fix and update workqueue usage
  md: use sector_t in bitmap_get_counter
  md: remove md_mutex locking.
  md: Fix regression with raid1 arrays without persistent metadata.