linux-kernel - [PATCH tip/core/rcu 09/18] vfs: abstract rcu_dereference

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Message-Id: <1266438584-29173-9-git-send-email-paulmck@linux.vnet.ibm.com>
Date:	Wed, 17 Feb 2010 12:29:35 -0800
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	linux-kernel@...r.kernel.org
Cc:	mingo@...e.hu, laijs@...fujitsu.com, dipankar@...ibm.com,
	akpm@...ux-foundation.org, mathieu.desnoyers@...ymtl.ca,
	josh@...htriplett.org, dvhltc@...ibm.com, niv@...ibm.com,
	tglx@...utronix.de, peterz@...radead.org, rostedt@...dmis.org,
	Valdis.Kletnieks@...edu, dhowells@...hat.com,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: [PATCH tip/core/rcu 09/18] vfs: abstract rcu_dereference_check for files-fdtable use

Create an rcu_dereference_check_fdtable() that encapsulates the
rcu_dereference_check() condition for fcheck_files() use.  This has
the beneficial side-effect of getting rid of a very long line.

Suggested-by: Peter Zijlstra <peterz@...radead.org>
Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
---
 include/linux/fdtable.h |   11 +++++++----
 1 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/include/linux/fdtable.h b/include/linux/fdtable.h
index 144412f..013dc52 100644
--- a/include/linux/fdtable.h
+++ b/include/linux/fdtable.h
@@ -57,11 +57,14 @@ struct files_struct {
 	struct file * fd_array[NR_OPEN_DEFAULT];
 };
 
-#define files_fdtable(files) \
-	(rcu_dereference_check((files)->fdt, \
+#define rcu_dereference_check_fdtable(files, fdtfd) \
+	(rcu_dereference_check((fdtfd), \
 			       rcu_read_lock_held() || \
 			       lockdep_is_held(&(files)->file_lock) || \
-			       atomic_read(&files->count) == 1))
+			       atomic_read(&(files)->count) == 1))
+
+#define files_fdtable(files) \
+		(rcu_dereference_check_fdtable((files), (files)->fdt))
 
 struct file_operations;
 struct vfsmount;
@@ -82,7 +85,7 @@ static inline struct file * fcheck_files(struct files_struct *files, unsigned in
 	struct fdtable *fdt = files_fdtable(files);
 
 	if (fd < fdt->max_fds)
-		file = rcu_dereference_check(fdt->fd[fd], rcu_read_lock_held() || lockdep_is_held(&files->file_lock) || atomic_read(&files->count) == 1);
+		file = rcu_dereference_check_fdtable(files, fdt->fd[fd]);
 	return file;
 }
 
-- 
1.6.6

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