On Fri, 5 Feb 2010, Miklos Szeredi wrote:
On Thu, 04 Feb 2010, Bodo Eggert wrote:
Miklos Szeredi <miklos@xxxxxxxxxx> wrote:
Additionally, return -EINVAL if an unknown flag is encountered. This
makes it possible for the caller to determine if a flag is supported
or not (at least on kernels with this patch).
There should be a guaranteed-to-be-invalid flag or flag-combination in
order to safely detect this feature.
It's difficult though, because the app would have to make sure the
detection itself would reliably fail, and with a different error.
Simply checking the kernel version might be easier.
Yes, that's exactly what I intend to make possible:
| ret = umount("/tmp/mkstmp", UMOUNT_IMPOSSIBLE_FLAG);
| if (ret != -1 || errno != -EINVAL)
| goto extended_mount_flags_are_not_supported;
Checking the kernel version is a bad idea, because the application might
be portable, or features might be backported. ¢¢
