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

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Message-ID: <YLkQtDZFG1xKoqE5@kroah.com>
Date:   Thu, 3 Jun 2021 19:26:12 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Jaegeuk Kim <jaegeuk@...nel.org>
Cc:     Daniel Rosenberg <drosen@...gle.com>, Chao Yu <chao@...nel.org>,
        linux-f2fs-devel@...ts.sourceforge.net,
        linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        Gabriel Krisman Bertazi <krisman@...labora.com>,
        kernel-team@...roid.com, stable@...r.kernel.org
Subject: Re: [PATCH v2 2/2] f2fs: Advertise encrypted casefolding in sysfs

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@...r.kernel.org # v5.11+
> > > Signed-off-by: Daniel Rosenberg <drosen@...gle.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?

greg k-h