Re: [libvirt] [PATCH 1/2] Introduce posix_fallocate() to allocate disk space

Using posix_fallocate() to allocate disk space and fill it with zeros is faster than writing the zeros block-by-block. Also, for backing file systems that support extents and the fallocate() syscall, this operation will give us a big speed boost. This also brings us the advantage of very less fragmentation for the chunk being allocated. For systems that don't support posix_fallocate(), fall back to safewrite().