Re: [libvirt] [PATCHv2 1/4] Change virFileOperation to return -errno (ie < 0) on error.

virFileOperation previously returned 0 on success, or the value of errno on failure. Although there are other functions in libvirt that use this convention, the preferred (and more common) convention is to return 0 on success and -errno (or simply -1 in some cases) on failure. This way the check for failure is always (ret < 0). * src/util/util.c - change virFileOperation and virFileOperationNoFork to return -errno on failure. * src/storage/storage_backend.c, src/qemu/qemu_driver.c - change the hook functions passed to virFileOperation to return -errno on failure.