Re: [PATCH v1 3/5] migration/ram: Don't explicitly unprotect when unregistering uffd-wp

[Juan Quintela]

David Hildenbrand <david@redhat.com> wrote:
> When unregistering uffd-wp, older kernels before commit f369b07c86143
> ("mm/uffd:reset write protection when unregister with wp-mode") won't
> clear the uffd-wp PTE bit. When re-registering uffd-wp, the previous
> uffd-wp PTE bits would trigger again. With above commit, the kernel will
> clear the uffd-wp PTE bits when unregistering itself.
>
> Consequently, we'll clear the uffd-wp PTE bits now twice -- whereby we
> don't care about clearing them at all: a new background snapshot will
> re-register uffd-wp and re-protect all memory either way.
>
> So let's skip the manual clearing of uffd-wp. If ever relevant, we
> could clear conditionally in uffd_unregister_memory() -- we just need a
> way to figure out more recent kernels.
>
> Signed-off-by: David Hildenbrand <david@redhat.com>

Reviewed-by: Juan Quintela <quintela@redhat.com>

Fixing a bug by removing code O:-)