This makes sure writing to a file fails early if the underlying
filesystem does not support fallocate. It also prevents partial header
write due to ENOSPC.
Another 3x performance boost for applications that walk the
directory tree.
Excerpt from performance.txt:
VERSION UNTAR LS RM
v0.4 48 1.5 5
v0.5-rc1 56 7 19
v0.5-rc1-1 54 4.1 9
v0.5-rc1-2 45 1.7 3.4 <---- THIS VERSION
Formerly, we called decryptPath for every name.
That resulted in a directory walk that reads in all diriv files
on the way.
Massive improvement for RM and LS (check performance.txt for details)
VERSION UNTAR RM LS
v0.4 48 5 1.5
v0.5-rc1 56 19 7
v0.5-rc1-1 54 9 4.1 <---- THIS VERSION