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From:   Yu Zhao <yuzhao@google.com>
Date:   Tue, 30 Aug 2022 16:25:24 -0600
Message-ID: <CAOUHufZrb_gkxaWfCLuFodRtCwGGdYjo2wvFW7kTiTkRbg4XNQ@mail.gmail.com>
Subject: Re: [PATCH v5 04/44] x86: asm: instrument usercopy in get_user() and put_user()
To:     Andrew Morton <akpm@linux-foundation.org>
Cc:     Alexander Potapenko <glider@google.com>,
        Marco Elver <elver@google.com>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Alexei Starovoitov <ast@kernel.org>,
        Andrey Konovalov <andreyknvl@google.com>,
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        Christoph Hellwig <hch@lst.de>,
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        David Rientjes <rientjes@google.com>,
        Dmitry Vyukov <dvyukov@google.com>,
        Eric Dumazet <edumazet@google.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Herbert Xu <herbert@gondor.apana.org.au>,
        Ilya Leoshkevich <iii@linux.ibm.com>,
        Ingo Molnar <mingo@redhat.com>, Jens Axboe <axboe@kernel.dk>,
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On Tue, Aug 30, 2022 at 4:05 PM Andrew Morton <akpm@linux-foundation.org> w=
rote:
>
> On Tue, 30 Aug 2022 16:23:44 +0200 Alexander Potapenko <glider@google.com=
> wrote:
>
> > >                  from init/do_mounts.c:2:
> > > ./include/linux/page-flags.h: In function =E2=80=98page_fixed_fake_he=
ad=E2=80=99:
> > > ./include/linux/page-flags.h:226:36: error: invalid use of undefined =
type =E2=80=98const struct page=E2=80=99
> > >   226 |             test_bit(PG_head, &page->flags)) {
> > >       |                                    ^~
> > > ./include/linux/bitops.h:50:44: note: in definition of macro =E2=80=
=98bitop=E2=80=99
> > >    50 |           __builtin_constant_p((uintptr_t)(addr) !=3D (uintpt=
r_t)NULL) && \
> > >       |                                            ^~~~
> > > ./include/linux/page-flags.h:226:13: note: in expansion of macro =E2=
=80=98test_bit=E2=80=99
> > >   226 |             test_bit(PG_head, &page->flags)) {
> > >       |             ^~~~~~~~
> > > ...
> >
> > Gotcha, this is a circular dependency: mm_types.h -> sched.h ->
> > kmsan.h -> gfp.h -> mmzone.h -> page-flags.h -> mm_types.h, where the
> > inclusion of sched.h into mm_types.h was only introduced in "mm:
> > multi-gen LRU: support page table walks" - that's why the problem was
> > missing in other trees.
>
> Ah, thanks for digging that out.
>
> Yu, that inclusion is regrettable.

Sorry for the trouble -- it's also superfluous because we don't call
lru_gen_use_mm() when switching to the kernel.

I've queued the following for now.

--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -3,7 +3,6 @@
 #define _LINUX_MM_TYPES_H

 #include <linux/mm_types_task.h>
-#include <linux/sched.h>

 #include <linux/auxvec.h>
 #include <linux/kref.h>
@@ -742,8 +741,7 @@ static inline void lru_gen_init_mm(struct mm_struct *mm=
)

 static inline void lru_gen_use_mm(struct mm_struct *mm)
 {
-       if (!(current->flags & PF_KTHREAD))
-               WRITE_ONCE(mm->lru_gen.bitmap, -1);
+       WRITE_ONCE(mm->lru_gen.bitmap, -1);
 }

 #else /* !CONFIG_LRU_GEN */