Regression(?) in Kernel 4.14 with mount (private/shared)

[Andrew Forgue <andrew@xxxxxxxxx>]

Hi There,

I'm running on CentOS 6.9 (with util-mount 2.17.2 (old!)) and Kernel 4.14.13.  It seems that since 4.13.6 the mount() syscall return value has changed from 0 to EINVAL:

In 4.13.6:

	# strace mount --make-private /srv/shared/work
	...
	mount("/dev/mapper/rootvg-sharedwork", "/srv/shared/work", "none", MS_NOSUID|MS_NOATIME|MS_PRIVATE, "pquota") = 0

In 4.14.13:

	# strace mount --make-private /srv/shared/work
	...
	mount("/dev/mapper/rootvg-sharedwork", "/srv/shared/work", "none", MS_NOSUID|MS_NOATIME|MS_PRIVATE, "pquota") = -1 EINVAL (Invalid argument)

I'm happy to help debug this as much as possible, but I'm not sure what the issue is.

The mount man page suggests that EINVAL will be returned if more flags other than MS_PRIVATE are supplied, so it looks like the old version of mount is doing the wrong thing (newer versions of mount from util-linux seem to do the right thing). However, upgrading util-linux is much more difficult for us than the kernel, and this looks like a regression?

Thanks,
Andrew