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Date:   Thu, 3 Jun 2021 10:53:26 -0700
From:   Jaegeuk Kim <jaegeuk@kernel.org>
To:     Greg KH <gregkh@linuxfoundation.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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 <YLkQtDZFG1xKoqE5@kroah.com>
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On 06/03, Greg KH wrote:
> On Thu, Jun 03, 2021 at 08:40:24AM -0700, Jaegeuk Kim wrote:
> > On 06/03, Greg KH 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");
> > > 
> > > This is a HUGE abuse of sysfs and should not be encouraged and added to.
> > 
> > This feature entry was originally added in 2017. Let me try to clean this up
> > after merging this.
> 
> Thank you.
> 
> > > Please make these "one value per file" and do not keep growing a single
> > > file that has to be parsed otherwise you will break userspace tools.
> > > 
> > > And I don't see a Documentation/ABI/ entry for this either :(
> > 
> > There is in Documentation/ABI/testing/sysfs-fs-f2fs.
> 
> So this new item was documented in the file before the kernel change was
> made?

Do we need to describe all the strings in this entry?

203 What:           /sys/fs/f2fs/<disk>/features
204 Date:           July 2017
205 Contact:        "Jaegeuk Kim" <jaegeuk@kernel.org>
206 Description:    Shows all enabled features in current device.

> 
> greg k-h