md: raid5: fix clearing of biofill operations

md: raid5: fix clearing of biofill operations

ops_complete_biofill() runs outside of spin_lock(&sh->lock) and clears the
'pending' and 'ack' bits.  Since the test_and_ack_op() macro only checks
against 'complete' it can get an inconsistent snapshot of pending work.

Move the clearing of these bits to handle_stripe5(), under the lock.

Signed-off-by: Dan Williams <[email protected]>
Tested-by: Joel Bertrand <[email protected]>
Signed-off-by: Neil Brown <[email protected]>
Cc: Stable <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>