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From: Suren Baghdasaryan <surenb@google.com>
Date: Fri, 2 Sep 2022 10:46:20 -0700
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Subject: Re: [RFC PATCH RESEND 04/28] mm: move mmap_lock assert function definitions
To: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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On Thu, Sep 1, 2022 at 11:23 PM Sebastian Andrzej Siewior
<bigeasy@linutronix.de> wrote:
>
> On 2022-09-01 16:24:09 [-0400], Kent Overstreet wrote:
> > > --- a/include/linux/mmap_lock.h
> > > +++ b/include/linux/mmap_lock.h
> > > @@ -60,6 +60,18 @@ static inline void __mmap_lock_trace_released(struct mm_struct *mm, bool write)
> > >
> > >  #endif /* CONFIG_TRACING */
> > >
> > > +static inline void mmap_assert_locked(struct mm_struct *mm)
> > > +{
> > > +   lockdep_assert_held(&mm->mmap_lock);
> > > +   VM_BUG_ON_MM(!rwsem_is_locked(&mm->mmap_lock), mm);
> >
> > These look redundant to me - maybe there's a reason the VM developers want both,
> > but I would drop the VM_BUG_ON() and just keep the lockdep_assert_held(), since
> > that's the standard way to write that assertion.
>
> Exactly. rwsem_is_locked() returns true only if the lock is "locked" not
> necessary by the caller. lockdep_assert_held() checks that the lock is
> locked by the caller - this is the important part.

Ok, if at the end of the day there is a consensus that this redundancy
should be removed then I'll do that in a patch separate from this
series. Please note that in this patch I'm not changing these
functions in any way, just moving them.

>
> Sebastian
>
> --
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