Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755789Ab0KZPHg (ORCPT ); Fri, 26 Nov 2010 10:07:36 -0500 Received: from casper.infradead.org ([85.118.1.10]:35535 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755135Ab0KZPBh (ORCPT ); Fri, 26 Nov 2010 10:01:37 -0500 Message-Id: <20101126145410.655255418@chello.nl> User-Agent: quilt/0.47-1 Date: Fri, 26 Nov 2010 15:38:50 +0100 From: Peter Zijlstra To: Andrea Arcangeli , Avi Kivity , Thomas Gleixner , Rik van Riel , Ingo Molnar , akpm@linux-foundation.org, Linus Torvalds Cc: linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, linux-mm@kvack.org, Benjamin Herrenschmidt , David Miller , Hugh Dickins , Mel Gorman , Nick Piggin , Peter Zijlstra , Paul McKenney , Yanmin Zhang , Stephen Rothwell Subject: [PATCH 07/21] mm: Use refcounts for page_lock_anon_vma() References: <20101126143843.801484792@chello.nl> Content-Disposition: inline; filename=mm-ref-page_lock_anon_vma.patch Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2303 Lines: 82 Convert page_lock_anon_vma() over to use refcounts. This is done for each of convertion of anon_vma from spinlock to mutex. Signed-off-by: Peter Zijlstra --- mm/rmap.c | 34 ++++++++++++++++++++++++---------- 1 file changed, 24 insertions(+), 10 deletions(-) Index: linux-2.6/mm/rmap.c =================================================================== --- linux-2.6.orig/mm/rmap.c +++ linux-2.6/mm/rmap.c @@ -332,9 +332,9 @@ void __init anon_vma_init(void) * that the anon_vma pointer from page->mapping is valid if there is a * mapcount, we can dereference the anon_vma after observing those. */ -struct anon_vma *page_lock_anon_vma(struct page *page) +struct anon_vma *page_get_anon_vma(struct page *page) { - struct anon_vma *anon_vma, *root_anon_vma; + struct anon_vma *anon_vma = NULL; unsigned long anon_mapping; rcu_read_lock(); @@ -345,8 +345,10 @@ struct anon_vma *page_lock_anon_vma(stru goto out; anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON); - root_anon_vma = ACCESS_ONCE(anon_vma->root); - spin_lock(&root_anon_vma->lock); + if (!atomic_inc_not_zero(&anon_vma->refcount)) { + anon_vma = NULL; + goto out; + } /* * If this page is still mapped, then its anon_vma cannot have been @@ -356,19 +358,31 @@ struct anon_vma *page_lock_anon_vma(stru * corrupt): with anon_vma_prepare() or anon_vma_fork() redirecting * anon_vma->root before page_unlock_anon_vma() is called to unlock. */ - if (page_mapped(page)) - return anon_vma; - - spin_unlock(&root_anon_vma->lock); + if (!page_mapped(page)) { + put_anon_vma(anon_vma); + anon_vma = NULL; + goto out; + } out: rcu_read_unlock(); - return NULL; + + return anon_vma; +} + +struct anon_vma *page_lock_anon_vma(struct page *page) +{ + struct anon_vma *anon_vma = page_get_anon_vma(page); + + if (anon_vma) + anon_vma_lock(anon_vma); + + return anon_vma; } void page_unlock_anon_vma(struct anon_vma *anon_vma) { anon_vma_unlock(anon_vma); - rcu_read_unlock(); + put_anon_vma(anon_vma); } /* -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/