Pull MD updates from Song:
"- md/bitmap: Optimal last page size, by Jon Derrick
- Various raid10 fixes, by Yu Kuai and Li Nan
- md: add error_handlers for raid0 and linear, by Mariusz Tkaczyk"
* 'md-next' of https://git.kernel.org/pub/scm/linux/kernel/git/song/md:
md/raid5: remove unused working_disks variable
md/raid10: don't call bio_start_io_acct twice for bio which experienced read error
md/raid10: fix memleak of md thread
md/raid10: fix memleak for 'conf->bio_split'
md/raid10: fix leak of 'r10bio->remaining' for recovery
md/raid10: don't BUG_ON() in raise_barrier()
md: fix soft lockup in status_resync
md: add error_handlers for raid0 and linear
md: Use optimal I/O size for last bitmap page
md: Fix types in sb writer
md: Move sb writer loop to its own function
md/raid10: Fix typo in comment (replacment -> replacement)
md: make kobj_type structures constant
md/raid10: fix null-ptr-deref in raid10_sync_request
md/raid10: fix task hung in raid10d