linux-ext4 - RE: [PATCH 2/3] f2fs: notify when device not supprt inlinecrypt

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Date:   Tue, 19 Apr 2022 03:14:51 +0000
From:   常凤楠 <changfengnan@...o.com>
To:     Eric Biggers <ebiggers@...nel.org>
CC:     "jaegeuk@...nel.org" <jaegeuk@...nel.org>,
        "chao@...nel.org" <chao@...nel.org>,
        "tytso@....edu" <tytso@....edu>,
        "adilger.kernel@...ger.ca" <adilger.kernel@...ger.ca>,
        "axboe@...nel.dk" <axboe@...nel.dk>,
        "linux-block@...r.kernel.org" <linux-block@...r.kernel.org>,
        "linux-ext4@...r.kernel.org" <linux-ext4@...r.kernel.org>,
        "linux-f2fs-devel@...ts.sourceforge.net" 
        <linux-f2fs-devel@...ts.sourceforge.net>
Subject: RE: [PATCH 2/3] f2fs: notify when device not supprt inlinecrypt



> -----Original Message-----
> From: Eric Biggers <ebiggers@...nel.org>
> Sent: Tuesday, April 19, 2022 6:27 AM
> To: 常凤楠 <changfengnan@...o.com>
> Cc: jaegeuk@...nel.org; chao@...nel.org; tytso@....edu;
> adilger.kernel@...ger.ca; axboe@...nel.dk; linux-block@...r.kernel.org;
> linux-ext4@...r.kernel.org; linux-f2fs-devel@...ts.sourceforge.net
> Subject: Re: [PATCH 2/3] f2fs: notify when device not supprt inlinecrypt
> 
> On Mon, Apr 18, 2022 at 07:34:52AM +0000, 常凤楠 wrote:
> > > -----Original Message-----
> > > From: Eric Biggers <ebiggers@...nel.org>
> > > Sent: Monday, April 18, 2022 3:22 PM
> > > To: 常凤楠 <changfengnan@...o.com>
> > > Cc: jaegeuk@...nel.org; chao@...nel.org; tytso@....edu;
> > > adilger.kernel@...ger.ca; axboe@...nel.dk;
> > > linux-block@...r.kernel.org; linux-ext4@...r.kernel.org;
> > > linux-f2fs-devel@...ts.sourceforge.net
> > > Subject: Re: [PATCH 2/3] f2fs: notify when device not supprt
> > > inlinecrypt
> > >
> > > On Mon, Apr 18, 2022 at 02:33:11PM +0800, Fengnan Chang via
> > > Linux-f2fs-devel wrote:
> > > > Notify when mount filesystem with -o inlinecrypt option, but the
> > > > device not support inlinecrypt.
> > > >
> > > > Signed-off-by: Fengnan Chang <changfengnan@...o.com>
> > >
> > > You didn't include a cover letter in this patchset.  Can you explain
> > > what problem this patchset is meant to solve?
> >
> > What I'm try to make is when devices not support inlinecrypt, do not show
> inlinecrypt in mount option.
> > When I test fscrypt first, it make me confused. Not a real problem, just make
> this logical more reasonable.
> > Do you think this needs to be revised?
> 
> Well, I'm just not sure we should do this, or at least by itself, given that
> support for inline encryption is not an either-or thing, and the inlinecrypt
> mount option is already documented to apply only to files where inline
> encryption can be used.  See Documentation/filesystems/fscrypt.rst:
> 
> 	Note that the "inlinecrypt" mount option just specifies to use inline
> 	encryption when possible; it doesn't force its use.  fscrypt will
> 	still fall back to using the kernel crypto API on files where the
> 	inline encryption hardware doesn't have the needed crypto capabilities
> 	(e.g. support for the needed encryption algorithm and data unit size)
> 	and where blk-crypto-fallback is unusable.  (For blk-crypto-fallback
> 	to be usable, it must be enabled in the kernel configuration with
> 	CONFIG_BLK_INLINE_ENCRYPTION_FALLBACK=y.) and not for other reasons
> 
> And Documentation/admin-guide/ext4.rst and
> Documentation/filesystems/f2fs.rst:
> 
> 	When possible, encrypt/decrypt the contents of encrypted files using the
> 	blk-crypto framework rather than filesystem-layer encryption. ...
> 
> If we do want to warn when inlinecrypt is given but inline encryption cannot
> be used, your patchset isn't enough since it only covers the case where no
> form of inline encryption is available at all, and not the case where some form
> of inline encryption is available but the filesystem can't use it.

Thanks for your explanation, this patchset has too many case to forget to handle...
Back to my first thought, maybe there should have one sysfs node to indicate the 
device support inlinecrypt or not ? So user can know it's device not support inlinecrypt
and not for other reasons.

Thanks.

> 
> - Eric