Re: [Qemu-devel] [PATCH v12 0/6] qcow2, raw: add preallocation=full and preallocation=falloc

[Richard W.M. Jones]

On Mon, Jul 28, 2014 at 04:48:46PM +0800, Hu Tao wrote:
> ping...
> 
> All the 6 patches have reviewed-by now.
> 
> On Fri, Jul 11, 2014 at 02:09:57PM +0800, Hu Tao wrote:
> > This series adds two preallocation mode to qcow2 and raw:
> > 
> > Option preallocation=full preallocates disk space for image by writing
> > zeros to disk, this ensures disk space in any cases.
> > 
> > Option preallocation=falloc preallocates disk space by calling
> > posix_fallocate(). This is faster than preallocation=full.

Sorry if this was discussed before, but why would anyone use
preallocation=full if preallocation=falloc was possible?

Shouldn't preallocation=full simply use posix_fallocate if it's
available, and fall back to writing zeroes if not?

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
virt-builder quickly builds VMs from scratch
http://libguestfs.org/virt-builder.1.html