linux-kernel - Re: [PATCH 05 of 66] compound

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Date:	Thu, 25 Nov 2010 17:21:58 +0100
From:	Andrea Arcangeli <aarcange@...hat.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Mel Gorman <mel@....ul.ie>, linux-mm@...ck.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org,
	Marcelo Tosatti <mtosatti@...hat.com>,
	Adam Litke <agl@...ibm.com>, Avi Kivity <avi@...hat.com>,
	Hugh Dickins <hugh.dickins@...cali.co.uk>,
	Rik van Riel <riel@...hat.com>,
	Dave Hansen <dave@...ux.vnet.ibm.com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Ingo Molnar <mingo@...e.hu>, Mike Travis <travis@....com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Christoph Lameter <cl@...ux-foundation.org>,
	Chris Wright <chrisw@...s-sol.org>, bpicco@...hat.com,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Balbir Singh <balbir@...ux.vnet.ibm.com>,
	"Michael S. Tsirkin" <mst@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Johannes Weiner <hannes@...xchg.org>,
	Daisuke Nishimura <nishimura@....nes.nec.co.jp>,
	Chris Mason <chris.mason@...cle.com>,
	Borislav Petkov <bp@...en8.de>
Subject: Re: [PATCH 05 of 66] compound_lock

On Thu, Nov 18, 2010 at 09:28:27AM -0800, Linus Torvalds wrote:
> On Thu, Nov 18, 2010 at 3:49 AM, Mel Gorman <mel@....ul.ie> wrote:
> >> +
> >> +static inline void compound_lock_irqsave(struct page *page,
> >> +                                      unsigned long *flagsp)
> >> +{
> >> +#ifdef CONFIG_TRANSPARENT_HUGEPAGE
> >> +     unsigned long flags;
> >> +     local_irq_save(flags);
> >> +     compound_lock(page);
> >> +     *flagsp = flags;
> >> +#endif
> >> +}
> >> +
> >
> > The pattern for spinlock irqsave passes in unsigned long, not unsigned
> > long *. It'd be nice if they matched.
> 
> Indeed. Just make the thing return the flags the way the normal
> spin_lock_irqsave() function does.

Done.

diff --git a/include/linux/mm.h b/include/linux/mm.h
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -320,15 +320,14 @@ static inline void compound_unlock(struc
 #endif
 }
 
-static inline void compound_lock_irqsave(struct page *page,
-					 unsigned long *flagsp)
+static inline unsigned long compound_lock_irqsave(struct page *page)
 {
+	unsigned long uninitialized_var(flags);
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
-	unsigned long flags;
 	local_irq_save(flags);
 	compound_lock(page);
-	*flagsp = flags;
 #endif
+	return flags;
 }
 
 static inline void compound_unlock_irqrestore(struct page *page,


diff --git a/mm/swap.c b/mm/swap.c
--- a/mm/swap.c
+++ b/mm/swap.c
@@ -94,7 +94,7 @@ static void put_compound_page(struct pag
 			 */
 			smp_mb();
 			/* page_head wasn't a dangling pointer */
-			compound_lock_irqsave(page_head, &flags);
+			flags = compound_lock_irqsave(page_head);
 			if (unlikely(!PageTail(page))) {
 				/* __split_huge_page_refcount run before us */
 				compound_unlock_irqrestore(page_head, flags);


Thanks,
Andrea
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