zfsonlinux/zfs — pull request #2649 by shenyan1 (2014-08-30 08:30:28+00:00)
Title: fix fallocate support

The default operation (mode is zero) of fallocate() allocates the disk space within the range specified by offset and len.
But the existed code can't handle mode=0.
http://man7.org/linux/man-pages/man2/fallocate.2.html