Pull MD updates from Shaohua Li:
 "A few fixes of MD for this merge window. Mostly bug fixes:

   - raid5 stripe batch fix from Amy

   - Read error handling for raid1 FailFast device from Gioh

   - raid10 recovery NULL pointer dereference fix from Guoqing

   - Support write hint for raid5 stripe cache from Mariusz

   - Fixes for device hot add/remove from Neil and Yufen

   - Improve flush bio scalability from Xiao"

* 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/shli/md:
  MD: fix lock contention for flush bios
  md/raid5: Assigning NULL to sh->batch_head before testing bit R5_Overlap of a stripe
  md/raid1: add error handling of read error from FailFast device
  md: fix NULL dereference of mddev->pers in remove_and_add_spares()
  raid5: copy write hint from origin bio to stripe
  md: fix two problems with setting the "re-add" device state.
  raid10: check bio in r10buf_pool_free to void NULL pointer dereference
  md: fix an error code format and remove unsed bio_sector