Re: [PATCH 0/2] fix dm-snap for dax

["Kani, Toshimitsu" <toshi.kani@hpe.com>]

Sorry, subject line should be "[PATCH 0/2] fix dm-snap for dax"
-Toshi

On Tue, 2016-06-28 at 13:37 -0600, Toshi Kani wrote:
> I noticed that dm-snap reloads DM table of target mapped-device, which
> fails for dax-capable device after dax support is added.  Ideally,
> adding dax support to dm-snap solves the issue, but it cannot be done
> easily.  This patch-set allows dm-snap to work with dax-capable target
> devices when bio-based operation is used.
> 
> dax operation is unsupported with dm-snap, such that:
>  a) After snapshot is taken, mount with dax option to a target device
>     or a snapshot device fails.  They can be mounted without dax.
>  b) After snapshot is taken to a dax-mounted target device, any writes 
>     to the target device fails (EIO).
> 
> b) can be protected by changing lvcreate to fail when snapshot is
> requested to a dax-mounted target device. 
> 
> - Patch 1 solves an error when lvremove is made to a snapshot device.
> - Patch 2 solves an error when lvcreate --snapshot is made to a dax-
>   capable device.
> 
> ---
> Toshi Kani (2):
>  1/2 dm: update table type check for dax
>  2/2 dm snap: add fake origin_direct_access
> 
> ---
>  drivers/md/dm-ioctl.c | 11 ++++++++++-
>  drivers/md/dm-snap.c  |  8 ++++++++
>  2 files changed, 18 insertions(+), 1 deletion(-)
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