discard on snapshot-origin target

["Marek Marczykowski-Górecki" <marmarek@invisiblethingslab.com>]

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Hi,

Is it possible to enable DISCARD support for snapshot-origin target?
Currently it returns EOPNOTSUPP even if underlying device does support
it. I know there are some cases when it isn't desirable (for example
mkfs.ext4 discards the entire device, which would trigger copyout to the
snapshot), but I can live with that. 

Or, if possible, better to prevent that copyout if discarded block(s)
were zeroed already. Which would handle the case of mkfs.ext4 on empty,
zeroed device.

I see that it may undesired in some cases, so maybe some configurable
option? Like module parameter or so?

-- 
Best Regards,
Marek Marczykowski-Górecki
Invisible Things Lab
A: Because it messes up the order in which people normally read text.
Q: Why is top-posting such a bad thing?

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