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

[Kani, Toshimitsu]

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.ÂÂIdeally,
> adding dax support to dm-snap solves the issue, but it cannot be done
> easily.ÂÂThis 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:
> Âa) After snapshot is taken, mount with dax option to a target device
> ÂÂÂÂor a snapshot device fails.ÂÂThey can be mounted without dax.
> Âb) After snapshot is taken to a dax-mounted target device, any writesÂ
> ÂÂÂÂto the target device fails (EIO).
> 
> b) can be protected by changing lvcreate to fail when snapshot is
> requested to a dax-mounted target device.Â
> 
> - 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-
> Â capable device.
> 
> ---
> Toshi Kani (2):
> Â1/2 dm: update table type check for dax
> Â2/2 dm snap: add fake origin_direct_access
> 
> ---
> Âdrivers/md/dm-ioctl.c | 11 ++++++++++-
> Âdrivers/md/dm-snap.cÂÂ|ÂÂ8 ++++++++
> Â2 files changed, 18 insertions(+), 1 deletion(-)
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