On Wed, Mar 9, 2022 at 11:35 AM Andreas Gruenbacher <agruenba@redhat.com> wrote:
>
> That's better, thanks.

Ok, can you give this one more test?

It has that simplified loop, but it also replaced the
FAULT_FLAG_KILLABLE with just passing in 'unlocked'.

I thought I didn't need to do that, but the "retry" loop inside
fixup_user_fault() will actually set that 'unlocked' thing even if the
caller doesn't care whether the mmap_sem was unlocked during the call,
so we have to pass in that pointer just to get that to work.

And we don't care if mmap_sem was dropped, because this loop doesn't
cache any vma information or anything like that, but we don't want to
get a NULL pointer oops just because fixup_user_fault() tries to
inform us about something we don't care about ;)

That incidentally gets us FAULT_FLAG_ALLOW_RETRY too, which is
probably a good thing anyway - it means that the mmap_sem will be
dropped if we wait for IO. Not likely a huge deal, but it's the
RightThing(tm) to do.

So this has some other changes there too, but on the whole the
function is now really quite simple. But it would be good to have one
final round of testing considering how many small details changed..

                      Linus