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

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Date:   Thu, 3 Jun 2021 08:40:24 -0700
From:   Jaegeuk Kim <jaegeuk@...nel.org>
To:     Greg KH <gregkh@...uxfoundation.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 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.

> 
> 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.

> 
> not good...
> 
> greg k-h