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Date:   Thu, 3 Jun 2021 22:38:48 -0700
From:   Jaegeuk Kim <jaegeuk@kernel.org>
To:     Eric Biggers <ebiggers@kernel.org>
Cc:     Daniel Rosenberg <drosen@google.com>, Chao Yu <chao@kernel.org>,
        linux-f2fs-devel@lists.sourceforge.net,
        linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
        Gabriel Krisman Bertazi <krisman@collabora.com>,
        kernel-team@android.com, stable@vger.kernel.org
Subject: Re: [PATCH v2 2/2] f2fs: Advertise encrypted casefolding in sysfs
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On 06/03, Eric Biggers wrote:
> On Thu, Jun 03, 2021 at 09:45:25PM -0700, Jaegeuk Kim wrote:
> > 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.
> > 
> 
> Yes, but in the on-disk case, encrypted_casefold is redundant because it simply
> means encrypt && casefold.  There is no encrypted_casefold flag on-disk.

I prefer to keep encrypted_casefold likewise kernel feature, which is more
intuitive to users.

> 
> - Eric