linux-kernel - Re: [PATCH] mm/hmm.c : Remove additional check for lockdep_assert

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Date:   Fri, 13 Mar 2020 09:17:22 +0530
From:   Souptick Joarder <jrdr.linux@...il.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Jérôme Glisse <jglisse@...hat.com>,
        Linux-MM <linux-mm@...ck.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm/hmm.c : Remove additional check for lockdep_assert_held()

On Fri, Mar 13, 2020 at 8:28 AM Andrew Morton <akpm@...ux-foundation.org> wrote:
>
> On Fri, 13 Mar 2020 07:41:00 +0530 Souptick Joarder <jrdr.linux@...il.com> wrote:
>
> > walk_page_range() already has a check for lockdep_assert_held().
> > So additional check for lockdep_assert_held() can be removed from
> > hmm_range_fault().
> >
> > ...
> >
> > --- a/mm/hmm.c
> > +++ b/mm/hmm.c
> > @@ -681,7 +681,6 @@ long hmm_range_fault(struct hmm_range *range, unsigned int flags)
> >       struct mm_struct *mm = range->notifier->mm;
> >       int ret;
> >
> > -     lockdep_assert_held(&mm->mmap_sem);
> >
> >       do {
> >               /* If range is no longer valid force retry. */
>
> It isn't very obvious that hmm_range_fault() is and will only be called
> from walk_page_range() (is it?)
>

Sorry Andrew, didn't get this part ?
* hmm_range_fault() is and will only be called
 from walk_page_range() (is it?) *