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    SubjectRe: [PATCH v5 04/44] x86: asm: instrument usercopy in get_user() and put_user()
    On Tue, Aug 30, 2022 at 5:00 PM Andrew Morton <akpm@linux-foundation.org> wrote:
    >
    > On Tue, 30 Aug 2022 16:25:24 -0600 Yu Zhao <yuzhao@google.com> wrote:
    >
    > > On Tue, Aug 30, 2022 at 4:05 PM Andrew Morton <akpm@linux-foundation.org> wrote:
    > > >
    > > > 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 ‘page_fixed_fake_head’:
    > > > > > ./include/linux/page-flags.h:226:36: error: invalid use of undefined type ‘const struct page’
    > > > > > 226 | test_bit(PG_head, &page->flags)) {
    > > > > > | ^~
    > > > > > ./include/linux/bitops.h:50:44: note: in definition of macro ‘bitop’
    > > > > > 50 | __builtin_constant_p((uintptr_t)(addr) != (uintptr_t)NULL) && \
    > > > > > | ^~~~
    > > > > > ./include/linux/page-flags.h:226:13: note: in expansion of macro ‘test_bit’
    > > > > > 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.
    >
    > Well, the rest of us want it too.
    >
    > > --- 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);
    > > }
    >
    > Doesn't apply. I did:
    >
    > --- a/include/linux/mm_types.h~mm-multi-gen-lru-support-page-table-walks-fix
    > +++ a/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>
    > @@ -742,11 +741,7 @@ static inline void lru_gen_init_mm(struc
    >
    > static inline void lru_gen_use_mm(struct mm_struct *mm)
    > {
    > - /* unlikely but not a bug when racing with lru_gen_migrate_mm() */
    > - VM_WARN_ON_ONCE(list_empty(&mm->lru_gen.list));

    Yes. I got a report that somebody tripped over this "unlikely"
    condition (and ascertained it's not a bug). So I deleted this part as
    well.

    Will refresh the series around rc5. Thanks.

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