[libvirt] [PATCH option 2] Use fsync() at the end of file allocation instead of O_DSYNC

[Jiri Denemark]

> > Instead of opening storage file with O_DSYNC, make sure data are written
> > to a disk only before we claim allocation has finished.
...
>   I would tend to prefer this patch on the basis that I would prefer a
> smaller change to the code at this point before the release. But the
> O_DSYNC was added after finding that cache effects could just break the
> qemu startup timeout in the test environment. I'm not 100% sure fsync()
> will have the same behaviour overall, it should but theory and practice
> may diverge :-)
>   So I'm tempted to go with this patch but we should validate it on testing
> before the end of the week.

Oh, the patch missed the release :-/ I pushed it now.

Jirka