From: Dan Williams <dan.j.williams@intel.com>
To: "Theodore Y. Ts'o" <tytso@mit.edu>
Cc: "Weiny, Ira" <ira.weiny@intel.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Jan Kara <jack@suse.cz>,
"Darrick J. Wong" <darrick.wong@oracle.com>,
Dave Chinner <david@fromorbit.com>,
Christoph Hellwig <hch@lst.de>, Jeff Moyer <jmoyer@redhat.com>,
linux-ext4 <linux-ext4@vger.kernel.org>,
linux-xfs <linux-xfs@vger.kernel.org>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>
Subject: Re: [PATCH RFC 3/8] fs/ext4: Disallow encryption if inode is DAX
Date: Wed, 15 Apr 2020 10:27:30 -0700 [thread overview]
Message-ID: <CAPcyv4jmBRsexpW2=SxqatbMK_u2aZcGnjeF+76=XwrCHfPoXA@mail.gmail.com> (raw)
In-Reply-To: <20200415160307.GJ90651@mit.edu>
On Wed, Apr 15, 2020 at 9:03 AM Theodore Y. Ts'o <tytso@mit.edu> wrote:
>
> On Mon, Apr 13, 2020 at 09:00:25PM -0700, ira.weiny@intel.com wrote:
> > From: Ira Weiny <ira.weiny@intel.com>
> >
> > Encryption and DAX are incompatible. Changing the DAX mode due to a
> > change in Encryption mode is wrong without a corresponding
> > address_space_operations update.
> >
> > Make the 2 options mutually exclusive by returning an error if DAX was
> > set first.
> >
> > Signed-off-by: Ira Weiny <ira.weiny@intel.com>
>
> The encryption flag is inherited from the containing directory, and
> directories can't have the DAX flag set, so anything we do in
> ext4_set_context() will be safety belt / sanity checking in nature.
>
> But we *do* need to figure out what we do with mount -o dax=always
> when the file system might have encrypted files. My previous comments
> about the verity flag and dax flag applies here.
>
> Also note that encrypted files are read/write so we must never allow
> the combination of ENCRPYT_FL and DAX_FL. So that may be something
> where we should teach __ext4_iget() to check for this, and declare the
> file system as corrupted if it sees this combination. (For VERITY_FL
> && DAX_FL that is a combo that we might want to support in the future,
> so that's probably a case where arguably, we should just ignore the
> DAX_FL for now.)
We also have a pending consideration for what MKTME (inline memory
encryption with programmable hardware keys) means for file-encryption
+ dax. Certainly kernel based software encryption is incompatible with
dax, but one of the hallway track discussions I wanted to have at LSF
is whether fscrypt is the right interface for managing inline memory
encryption. For now, disallowing ENCRPYT_FL + DAX_FL seems ok if
ENCRPYT_FL always means software encryption, but this is something to
circle back to once we get MKTME implemented for volume encryption and
start to look at finer grained (per-directory key) encryption.
next prev parent reply other threads:[~2020-04-15 17:27 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-14 4:00 [PATCH RFC 0/8] Enable ext4 support for per-file/directory DAX operations ira.weiny
2020-04-14 4:00 ` [PATCH RFC 1/8] fs/ext4: Narrow scope of DAX check in setflags ira.weiny
2020-04-15 11:45 ` Jan Kara
2020-04-14 4:00 ` [PATCH RFC 2/8] fs/ext4: Disallow verity if inode is DAX ira.weiny
2020-04-15 11:58 ` Jan Kara
2020-04-15 12:00 ` Jan Kara
2020-04-15 15:55 ` Theodore Y. Ts'o
2020-04-15 19:21 ` Ira Weiny
2020-04-15 19:14 ` Ira Weiny
2020-04-16 1:29 ` Eric Biggers
2020-04-16 3:48 ` Ira Weiny
2020-04-15 20:34 ` Ira Weiny
2020-04-14 4:00 ` [PATCH RFC 3/8] fs/ext4: Disallow encryption " ira.weiny
2020-04-15 12:02 ` Jan Kara
2020-04-15 20:35 ` Ira Weiny
2020-04-15 16:03 ` Theodore Y. Ts'o
2020-04-15 17:27 ` Dan Williams [this message]
2020-04-15 19:54 ` Ira Weiny
2020-04-21 18:41 ` Ira Weiny
2020-04-21 18:56 ` Darrick J. Wong
2020-04-14 4:00 ` [PATCH RFC 4/8] fs/ext4: Introduce DAX inode flag ira.weiny
2020-04-15 12:08 ` Jan Kara
2020-04-15 20:39 ` Ira Weiny
2020-04-16 10:32 ` Jan Kara
2020-04-16 18:01 ` Theodore Y. Ts'o
2020-04-16 16:25 ` Darrick J. Wong
2020-04-16 22:33 ` Ira Weiny
2020-04-16 22:49 ` Darrick J. Wong
2020-04-17 0:37 ` Ira Weiny
2020-04-17 1:57 ` Darrick J. Wong
2020-04-17 2:20 ` Ira Weiny
2020-04-17 6:43 ` Andreas Dilger
2020-04-17 17:19 ` Ira Weiny
2020-04-14 4:00 ` [PATCH RFC 5/8] fs/ext4: Make DAX mount option a tri-state ira.weiny
2020-04-15 12:51 ` Jan Kara
2020-04-14 4:00 ` [PATCH RFC 6/8] fs/ext4: Update ext4_should_use_dax() ira.weiny
2020-04-15 13:58 ` Jan Kara
2020-04-17 17:16 ` Ira Weiny
2020-04-14 4:00 ` [PATCH RFC 7/8] fs/ext4: Only change S_DAX on inode load ira.weiny
2020-04-15 14:03 ` Jan Kara
2020-04-17 17:18 ` Ira Weiny
2020-04-14 4:00 ` [PATCH RFC 8/8] Documentation/dax: Update DAX enablement for ext4 ira.weiny
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