Re: mm: delay rmap removal until after TLB flush

[Gerald Schaefer <gerald.schaefer@linux.ibm.com>]

On Wed, 2 Nov 2022 10:55:10 -0700
Linus Torvalds <torvalds@linux-foundation.org> wrote:

> On Wed, Nov 2, 2022 at 2:15 AM Christian Borntraeger
> <borntraeger@linux.ibm.com> wrote:
> >
> > It certainly needs a build fix for s390:
> >
> > In file included from kernel/sched/core.c:78:
> > ./arch/s390/include/asm/tlb.h: In function '__tlb_remove_page_size':
> > ./arch/s390/include/asm/tlb.h:50:17: error: implicit declaration of function 'page_zap_pte_rmap' [-Werror=implicit-function-declaration]
> >     50 |                 page_zap_pte_rmap(page);
> >        |                 ^~~~~~~~~~~~~~~~~
> 
> Hmm. I'm not sure if I can add a
> 
>    #include <linux/rmap.h>
> 
> to that s390 asm header file without causing more issues.
> 
> The minimal damage would probably be to duplicate the declaration of
> page_zap_pte_rmap() in the s390 asm/tlb.h header where it is used.
> 
> Not pretty to have two different declarations of that thing, but
> anything that then includes both <asm/tlb.h> and <linux/rmap.h> (which
> is much of mm) would then verify the consistency of  them.
> 
> So I'll do that minimal fix and update that branch, but if s390 people
> end up having a better fix, please holler.

It compiles now with your duplicate declaration, but adding the #include
also did not cause any damage, so that should also be OK.