Re: [Qemu-devel] [PATCH v13 5/6] raw-posix: Add full preallocation option

[Hu Tao]

On Fri, Aug 29, 2014 at 09:48:01AM +0100, Richard W.M. Jones wrote:
> On Fri, Aug 29, 2014 at 04:33:12PM +0800, Hu Tao wrote:
> > +    if (prealloc == PREALLOC_MODE_FULL) {
> > +        /* posix_fallocate() doesn't set errno. */
> > +        result = -posix_fallocate(fd, 0, total_size);
> > +        if (result != 0) {
> 
> Is it better to test:
> 
>   result != ENOSYS && result != EOPNOTSUPP
> 
> here?

posix_fallocate() doesn't return ENOSYS or EOPNOTSUPP. All the errors
returned by posix_fallocate() apply to writing zeros, too. that is, if
posix_fallocate() returns an error, we should not do writing zeros,
neither.

I'm wondering what is the right way to test if posix_fallocate() is
supported, something like AC_CHECK_FUNC? how?

Regards,
Hu

> 
> I think this is definitely the right approach.
> 
> Rich.
> 
> 
> -- 
> Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
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