linux-kernel - Re: [PATCH v7 18/27] mm: Introduce do_mmap

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Date:   Fri, 7 Jun 2019 09:47:07 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Yu-cheng Yu <yu-cheng.yu@...el.com>
Cc:     x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-mm@...ck.org,
        linux-arch@...r.kernel.org, linux-api@...r.kernel.org,
        Arnd Bergmann <arnd@...db.de>,
        Andy Lutomirski <luto@...capital.net>,
        Balbir Singh <bsingharora@...il.com>,
        Borislav Petkov <bp@...en8.de>,
        Cyrill Gorcunov <gorcunov@...il.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Eugene Syromiatnikov <esyr@...hat.com>,
        Florian Weimer <fweimer@...hat.com>,
        "H.J. Lu" <hjl.tools@...il.com>, Jann Horn <jannh@...gle.com>,
        Jonathan Corbet <corbet@....net>,
        Kees Cook <keescook@...omium.org>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Nadav Amit <nadav.amit@...il.com>,
        Oleg Nesterov <oleg@...hat.com>, Pavel Machek <pavel@....cz>,
        Randy Dunlap <rdunlap@...radead.org>,
        "Ravi V. Shankar" <ravi.v.shankar@...el.com>,
        Vedvyas Shanbhogue <vedvyas.shanbhogue@...el.com>,
        Dave Martin <Dave.Martin@....com>
Subject: Re: [PATCH v7 18/27] mm: Introduce do_mmap_locked()

On Fri, Jun 07, 2019 at 09:43:22AM +0200, Peter Zijlstra wrote:
> On Thu, Jun 06, 2019 at 01:06:37PM -0700, Yu-cheng Yu wrote:
> > There are a few places that need do_mmap() with mm->mmap_sem held.
> > Create an in-line function for that.
> > 
> > Signed-off-by: Yu-cheng Yu <yu-cheng.yu@...el.com>
> > ---
> >  include/linux/mm.h | 18 ++++++++++++++++++
> >  1 file changed, 18 insertions(+)
> > 
> > diff --git a/include/linux/mm.h b/include/linux/mm.h
> > index 398f1e1c35e5..7cf014604848 100644
> > --- a/include/linux/mm.h
> > +++ b/include/linux/mm.h
> > @@ -2411,6 +2411,24 @@ static inline void mm_populate(unsigned long addr, unsigned long len)
> >  static inline void mm_populate(unsigned long addr, unsigned long len) {}
> >  #endif
> >  
> > +static inline unsigned long do_mmap_locked(unsigned long addr,
> > +	unsigned long len, unsigned long prot, unsigned long flags,
> > +	vm_flags_t vm_flags)
> > +{
> > +	struct mm_struct *mm = current->mm;
> > +	unsigned long populate;
> > +
> > +	down_write(&mm->mmap_sem);
> > +	addr = do_mmap(NULL, addr, len, prot, flags, vm_flags, 0,
> > +		       &populate, NULL);
> 
> Funny thing how do_mmap() takes a file pointer as first argument and
> this thing explicitly NULLs that. That more or less invalidates the name
> do_mmap_locked().
> 
> > +	up_write(&mm->mmap_sem);
> > +
> > +	if (populate)
> > +		mm_populate(addr, populate);
> > +
> > +	return addr;
> > +}

You also don't retain that last @uf argument.

I'm thikning you're better off adding a helper to the cet.c file; call
it cet_mmap() or whatever.