When a file is partially truncated, we first check to see if the

When a file is partially truncated, we first check to see if the
new file end will land in the middle of a file hole. Since the last
block of a file must always be allocated, the hole is filled by
allocating a block at that location. If the hole being filled is
a direct block, then the truncation may eventually reduce the
full sized block down to a fragment. When running with soft
updates, it is necessary to FSYNC the file after allocating the
block and before creating the fragment to avoid triggering a
soft updates inconsistency when the block unexpectedly shrinks.

Found by:	Matthew Dillon <dillon@apollo.backplane.com>
MFC after:	1 week