From: Andrew Morton <akpm@linux-foundation.org>
To: Souptick Joarder <jrdr.linux@gmail.com>
Cc: "Jérôme Glisse" <jglisse@redhat.com>,
Linux-MM <linux-mm@kvack.org>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mm/hmm.c : Remove additional check for lockdep_assert_held()
Date: Thu, 12 Mar 2020 20:57:41 -0700 [thread overview]
Message-ID: <20200312205741.e97a201037103bbf51e1df40@linux-foundation.org> (raw)
In-Reply-To: <CAFqt6zZ4ceum_SHmQgub8EKJxNQ26_-UfzvK-kcejqH67QHHtA@mail.gmail.com>
On Fri, 13 Mar 2020 09:17:22 +0530 Souptick Joarder <jrdr.linux@gmail.com> wrote:
> On Fri, Mar 13, 2020 at 8:28 AM Andrew Morton <akpm@linux-foundation.org> wrote:
> >
> > On Fri, 13 Mar 2020 07:41:00 +0530 Souptick Joarder <jrdr.linux@gmail.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 /* If range is no longer valid force retry.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?) *
The patch assumes that hmm_range_fault() will only ever be called via
walk_page_range(). How do we know this is the case? And that it
always will be the case?
next prev parent reply other threads:[~2020-03-13 3:57 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-13 2:11 [PATCH] mm/hmm.c : Remove additional check for lockdep_assert_held() Souptick Joarder
2020-03-13 2:58 ` Andrew Morton
2020-03-13 3:47 ` Souptick Joarder
2020-03-13 3:57 ` Andrew Morton [this message]
2020-03-13 4:22 ` Souptick Joarder
2020-03-13 12:22 ` Jason Gunthorpe
2020-03-22 15:16 ` Souptick Joarder
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