This test is for preallocation test. If the disk is full, just with a prealloc
file has some free space that prealloc early. We need to check whether the write
to the free space is success or not.
Signed-off-by: Wu Bo <Wu.Bo@cn.fujitsu.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
WuBo