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Message-ID: <20171012155227.o3dql7teq6gkghfo@thunk.org> Date: Thu, 12 Oct 2017 11:52:27 -0400 From: Theodore Ts'o <tytso@....edu> To: Ross Zwisler <ross.zwisler@...ux.intel.com> Cc: Jan Kara <jack@...e.cz>, linux-kernel@...r.kernel.org, Andreas Dilger <adilger.kernel@...ger.ca>, Christoph Hellwig <hch@....de>, Dan Williams <dan.j.williams@...el.com>, Dave Chinner <david@...morbit.com>, linux-ext4@...r.kernel.org, linux-nvdimm@...ts.01.org, stable@...r.kernel.org Subject: Re: [PATCH v2 1/5] ext4: prevent data corruption with inline data + DAX 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 <ross.zwisler@...ux.intel.com> > CC: stable@...r.kernel.org Thanks, applied. - Ted
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