Re: [PATCH] ext4: Check for encryption feature before fscrypt_process_policy()

[Eric Biggers]

On Thu, Sep 22, 2016 at 06:38:03PM -0400, Theodore Ts'o wrote:
> 
> I think it's fine to fix it now in upstream.  It might cause some
> problems for Cyanogen developers if they want to try to use an
> upstream kernel and also enable the ext4 encryption feature, but the
> fix to make_ext4fs isn't all that hard.

Would it make sense to at least provide a helpful error message in the kernel
log?  For example:

                if (!ext4_has_feature_encrypt(sb)) {
                        ext4_msg(sb, KERN_INFO,
                                 "warning: process `%s' tried to set "
                                 "encryption policy on filesystem without "
                                 "encryption enabled.  This is not supported.  "
                                 "Use 'tune2fs -O encrypt' to enable the "
                                 "encryption feature flag first.",
                                 current->comm);
                        return -EOPNOTSUPP;
                }

Eric