linux-kernel - [Patch v2] rcu: update the CONFIG logic in include/linux/pagemap.h

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Date:	Wed,  6 Apr 2011 14:32:48 +0800
From:	Amerigo Wang <amwang@...hat.com>
To:	linux-kernel@...r.kernel.org
Cc:	akpm@...ux-foundation.org,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	WANG Cong <amwang@...hat.com>, Mel Gorman <mel@....ul.ie>,
	Minchan Kim <minchan.kim@...il.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
Subject: [Patch v2] rcu: update the CONFIG logic in include/linux/pagemap.h

TREE_RCU depends on !PREEMPT && SMP, when !CONFIG_SMP is true, CONFIG_TREE_RCU
will be false, thus "!defined(CONFIG_SMP) && defined(CONFIG_TREE_RCU)"
is always false.

Paul suggested to update the logic to
!defined(CONFIG_SMP) && defined(CONFIG_TREE_PREEMPT_RCU).

Cc: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
Signed-off-by: WANG Cong <amwang@...hat.com>

---
 include/linux/pagemap.h |    9 +++------
 1 files changed, 3 insertions(+), 6 deletions(-)

diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index c119506..a296d7c 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -133,10 +133,9 @@ static inline int page_cache_get_speculative(struct page *page)
 {
 	VM_BUG_ON(in_interrupt());
 
-#if !defined(CONFIG_SMP) && defined(CONFIG_TREE_RCU)
-# ifdef CONFIG_PREEMPT
+#if !defined(CONFIG_SMP) && defined(CONFIG_TREE_PREEMPT_RCU)
+	/* Must have CONFIG_PREEMPT here, implied by CONFIG_TREE_PREEMPT_RCU. */
 	VM_BUG_ON(!in_atomic());
-# endif
 	/*
 	 * Preempt must be disabled here - we rely on rcu_read_lock doing
 	 * this for us.
@@ -171,10 +170,8 @@ static inline int page_cache_add_speculative(struct page *page, int count)
 {
 	VM_BUG_ON(in_interrupt());
 
-#if !defined(CONFIG_SMP) && defined(CONFIG_TREE_RCU)
-# ifdef CONFIG_PREEMPT
+#if !defined(CONFIG_SMP) && defined(CONFIG_TREE_PREEMPT_RCU)
 	VM_BUG_ON(!in_atomic());
-# endif
 	VM_BUG_ON(page_count(page) == 0);
 	atomic_add(count, &page->_count);
 
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