On Mon, Aug 09, 2021 at 12:52:35PM +0100, Pavel Begunkov wrote:

For the bug description see 2/2. As mentioned there the current problems
is because of generic_write_checks(), but there was also a similar case
fixed in 5.12, which should have been triggerable by normal
write(2)/read(2) and others.

It may be better to enforce reexpands as a long term solution, but for
now this patchset is quickier and easier to backport.

	Umm...  Won't that screw the cases where we *are* doing proper
reexpands?  AFAICS, with your patches that flag doesn't go away once
it had been set...