Re: [PATCH v2 2/2] f2fs: Advertise encrypted casefolding in sysfs

[Eric Biggers]

On Thu, Jun 03, 2021 at 09:50:38AM +0000, Daniel Rosenberg wrote:
> Older kernels don't support encryption with casefolding. This adds
> the sysfs entry encrypted_casefold to show support for those combined
> features. Support for this feature was originally added by
> commit 7ad08a58bf67 ("f2fs: Handle casefolding with Encryption")
> 
> Fixes: 7ad08a58bf67 ("f2fs: Handle casefolding with Encryption")
> Cc: stable@xxxxxxxxxxxxxxx # v5.11+
> Signed-off-by: Daniel Rosenberg <drosen@xxxxxxxxxx>
> ---
>  fs/f2fs/sysfs.c | 15 +++++++++++++--
>  1 file changed, 13 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/f2fs/sysfs.c b/fs/f2fs/sysfs.c
> index 09e3f258eb52..6604291a3cdf 100644
> --- a/fs/f2fs/sysfs.c
> +++ b/fs/f2fs/sysfs.c
> @@ -161,6 +161,9 @@ static ssize_t features_show(struct f2fs_attr *a,
>  	if (f2fs_sb_has_compression(sbi))
>  		len += scnprintf(buf + len, PAGE_SIZE - len, "%s%s",
>  				len ? ", " : "", "compression");
> +	if (f2fs_sb_has_casefold(sbi) && f2fs_sb_has_encrypt(sbi))
> +		len += scnprintf(buf + len, PAGE_SIZE - len, "%s%s",
> +				len ? ", " : "", "encrypted_casefold");
>  	len += scnprintf(buf + len, PAGE_SIZE - len, "%s%s",
>  				len ? ", " : "", "pin_file");
>  	len += scnprintf(buf + len, PAGE_SIZE - len, "\n");
> @@ -579,6 +582,7 @@ enum feat_id {
>  	FEAT_CASEFOLD,
>  	FEAT_COMPRESSION,
>  	FEAT_TEST_DUMMY_ENCRYPTION_V2,
> +	FEAT_ENCRYPTED_CASEFOLD,
>  };

Actually looking at it more closely, this patch is wrong.

It only makes sense to declare "encrypted_casefold" as a feature of the
filesystem implementation, i.e. /sys/fs/f2fs/features/encrypted_casefold.

It does *not* make sense to declare it as a feature of a particular filesystem
instance, i.e. /sys/fs/f2fs/$disk/features, as it is already implied by the
filesystem instance having both the encryption and casefold features enabled.

Can we add /sys/fs/f2fs/features/encrypted_casefold only?

- Eric