Use bitmap_set() instead of using set_bit() for each bit.  This conversion
is valid because the bitmap is private in the function call and atomic
bitops were unnecessary.

This also includes minor change.
- Use bitmap_copy() for shorter typing
Signed-off-by: NAkinobu Mita <akinobu.mita@gmail.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>