The fix for this issue has been merged in v5.6-rc7 and is part of the v5.6 release. The commit in upstream is:
763802b53a42 x86/mm: split vmalloc_sync_all()
This has also been backported to all current LTS kernels except 3.16
in the following releases:
v4.4.218
v4.9.218
v4.14.175
v4.19.113
v5.4.28
