Nothing too big here.
- define the size of the buffer used for consuming ignored
incoming data using a symbolic constant
- simplify the condition determining whether to unmap the page
in write_partial_msg_pages(): do it for crc but not if the
page is the zero page
Signed-off-by: Alex Elder <elder@dreamhost.com>
Signed-off-by: Sage Weil <sage@newdream.net>