67f586a8c1
Unlike disk devices ZVOLs process all requests synchronously. That makes impossible sending multiple requests to them from single thread. From the other side ZVOLs have real d_read/d_write methods, which unlike d_strategy can handle uio scatter/gather and have no strict I/O size limitations. So, if ZVOL in "dev" mode is detected, use of d_read/d_write methods instead of d_strategy allows to avoid pointless splitting of large requests into MAXPHYS (128K) sized chunks. MFC after: 1 week