From: Theodore Ts'o Subject: Re: [PATCH v2 1/5] ext4: prevent data corruption with inline data + DAX Date: Thu, 12 Oct 2017 11:52:27 -0400 Message-ID: <20171012155227.o3dql7teq6gkghfo@thunk.org> References: <20170912050526.7627-1-ross.zwisler@linux.intel.com> <20170912050526.7627-2-ross.zwisler@linux.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Jan Kara , linux-kernel@vger.kernel.org, Andreas Dilger , Christoph Hellwig , Dan Williams , Dave Chinner , linux-ext4@vger.kernel.org, linux-nvdimm@lists.01.org, stable@vger.kernel.org To: Ross Zwisler Return-path: Content-Disposition: inline In-Reply-To: <20170912050526.7627-2-ross.zwisler@linux.intel.com> Sender: stable-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org On Mon, Sep 11, 2017 at 11:05:22PM -0600, Ross Zwisler wrote: > If an inode has inline data it is currently prevented from using DAX by a > check in ext4_set_inode_flags(). When the inode grows inline data via > ext4_create_inline_data() or removes its inline data via > ext4_destroy_inline_data_nolock(), the value of S_DAX can change. > > Currently these changes are unsafe because we don't hold off page faults > and I/O, write back dirty radix tree entries and invalidate all mappings. > There are also issues with mm-level races when changing the value of S_DAX, > as well as issues with the VM_MIXEDMAP flag: > > https://www.spinics.net/lists/linux-xfs/msg09859.html > > The unsafe transition of S_DAX can reliably cause data corruption, as shown > by the following fstest: > > https://patchwork.kernel.org/patch/9948381/ > > Fix this issue by preventing the DAX mount option from being used on > filesystems that were created to support inline data. Inline data is an > option given to mkfs.ext4. > > Signed-off-by: Ross Zwisler > CC: stable@vger.kernel.org Thanks, applied. - Ted