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From: Ira Weiny <ira.weiny@intel.com>
To: "Theodore Y. Ts'o" <tytso@mit.edu>
Cc: linux-kernel@vger.kernel.org, Jan Kara <jack@suse.cz>,
	"Darrick J. Wong" <darrick.wong@oracle.com>,
	Dan Williams <dan.j.williams@intel.com>,
	Dave Chinner <david@fromorbit.com>,
	Christoph Hellwig <hch@lst.de>, Jeff Moyer <jmoyer@redhat.com>,
	linux-ext4@vger.kernel.org, linux-xfs@vger.kernel.org,
	linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH RFC 3/8] fs/ext4: Disallow encryption if inode is DAX
Date: Wed, 15 Apr 2020 12:54:34 -0700	[thread overview]
Message-ID: <20200415195433.GC2305801@iweiny-DESK2.sc.intel.com> (raw)
In-Reply-To: <20200415160307.GJ90651@mit.edu>

On Wed, Apr 15, 2020 at 12:03:07PM -0400, Theodore Y. Ts'o 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,

But they can have FS_XFLAG_DAX 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.

:-( agreed.

FWIW without these patches an inode which has encrypt or verity set is already
turning off DAX...  So we already have a '-o dax' flag which is not "always".

:-(

Unfortunately the 'always' designation kind of breaks semantically but it is
equal to the current mount option.

> 
> 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.

ok...

> (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.)

ok...

Ira


  parent reply	other threads:[~2020-04-15 19:54 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
2020-04-15 19:54     ` Ira Weiny [this message]
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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