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

[Jaegeuk Kim <jaegeuk@kernel.org>]

On 06/03, Eric Biggers wrote:
> 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@vger.kernel.org # v5.11+
> > Signed-off-by: Daniel Rosenberg <drosen@google.com>
> > ---
> >  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?

wait.. /sys/fs/f2fs/features/encrypted_casefold is on by
CONFIG_FS_ENCRYPTION && CONFIG_UNICODE.
OTOH, /sys/fs/f2fs/$dis/feature_list/encrypted_casefold is on by
on-disk features: F2FS_FEATURE_ENCRYPT and F2FS_FEATURE_CASEFOLD.

> 
> - Eric