Re: [PATCH v13 0/5] UFFD write-tracking migration/snapshots

[Peter Xu]

On Thu, Feb 11, 2021 at 10:09:58PM +0100, David Hildenbrand wrote:
> The issue is when the discard happened before starting the snapshot. 
> Write-protection won‘t work and the zeroed content won‘t be retained in the 
> snapshot.

I see what you mean now, and iiuc it will only be a problem if init_on_free=1.
I think CONFIG_INIT_ON_FREE_DEFAULT_ON should be off for most distros, so the
impact should be small, I think.  I thought about it, but indeed I didn't see a
good way to fix this if without fixing the zero page copy for live snapshot.

-- 
Peter Xu