linux-kernel - Re: [PATCH 2/5] mm: gup: add __get_user_pages_unlocked to customize gup

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Message-ID: <20141030174309.GL19606@redhat.com>
Date:	Thu, 30 Oct 2014 18:43:09 +0100
From:	Andrea Arcangeli <aarcange@...hat.com>
To:	"Kirill A. Shutemov" <kirill@...temov.name>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	Michel Lespinasse <walken@...gle.com>,
	Andrew Jones <drjones@...hat.com>,
	Hugh Dickins <hughd@...gle.com>, Mel Gorman <mgorman@...e.de>,
	Andres Lagar-Cavilla <andreslc@...gle.com>,
	Minchan Kim <minchan@...nel.org>,
	KOSAKI Motohiro <kosaki.motohiro@...il.com>,
	"\\\"Dr. David Alan Gilbert\\\"" <dgilbert@...hat.com>,
	Peter Feiner <pfeiner@...gle.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	James Bottomley <James.Bottomley@...senPartnership.com>,
	David Miller <davem@...emloft.net>,
	Steve Capper <steve.capper@...aro.org>,
	Johannes Weiner <jweiner@...hat.com>
Subject: Re: [PATCH 2/5] mm: gup: add __get_user_pages_unlocked to customize
 gup_flags

On Thu, Oct 30, 2014 at 02:17:37PM +0200, Kirill A. Shutemov wrote:
> On Wed, Oct 29, 2014 at 05:35:17PM +0100, Andrea Arcangeli wrote:
> > diff --git a/mm/gup.c b/mm/gup.c
> > index a8521f1..01534ff 100644
> > --- a/mm/gup.c
> > +++ b/mm/gup.c
> > @@ -591,9 +591,9 @@ static __always_inline long __get_user_pages_locked(struct task_struct *tsk,
> >  						int write, int force,
> >  						struct page **pages,
> >  						struct vm_area_struct **vmas,
> > -						int *locked, bool notify_drop)
> > +						int *locked, bool notify_drop,
> > +						unsigned int flags)
> 
> Argument list getting too long. Should we consider packing them into a
> struct?

It's __always_inline, so it's certainly not a runtime concern. The
whole point of using __always_inline is to optimize away certain
branches at build time.

If this about cleaning it up and not for changing the runtime (which I
think couldn't get any better because of the __always_inline), we
should at least make certain gcc can still see through the structure
offsets to delete the same code blocks at build time if possible,
before doing the change.
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