Re: [PATCH v2 5/7] ext4: fix up test_dummy_encryption handling for new mount API

[Eric Biggers <ebiggers@kernel.org>]

A couple corrections I'll include in the next version:

On Sat, Apr 30, 2022 at 10:08:55PM -0700, Eric Biggers wrote:
> +	if (fc->purpose == FS_CONTEXT_FOR_RECONFIGURE) {
> +		if (fscrypt_dummy_policies_equal(&sbi->s_dummy_enc_policy,
> +						 &ctx->dummy_enc_policy))
> +			return 0;
>  		ext4_msg(NULL, KERN_WARNING,
> -			 "Can't set test_dummy_encryption on remount");
> +			 "Can't set or change test_dummy_encryption on remount");
>  		return -EINVAL;
>  	}

I think this needs to be 'fc->purpose == FS_CONTEXT_FOR_RECONFIGURE ||
fscrypt_is_dummy_policy_set(&sbi->s_dummy_enc_policy)', since ext4 can parse
mount options from both s_mount_opts and the regular mount options.

> +static void ext4_apply_test_dummy_encryption(struct ext4_fs_context *ctx,
> +                                            struct super_block *sb)
> +{
> +	if (!fscrypt_is_dummy_policy_set(&ctx->dummy_enc_policy))
> +		return;

To handle remounts correctly, this needs to be
'!fscrypt_is_dummy_policy_set(&ctx->dummy_enc_policy) ||
fscrypt_is_dummy_policy_set(&EXT4_SB(sb)->s_dummy_enc_policy)'.

- Eric