linux-kernel - [PATCH tip/core/rcu 6/8] vfs: apply lockdep-based checking to rcu

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Date:	Mon,  4 Jan 2010 18:04:09 -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>,
	Alexander Viro <viro@...iv.linux.org.uk>
Subject: [PATCH tip/core/rcu 6/8] vfs: apply lockdep-based checking to rcu_dereference() uses

From: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>

Add lockdep-ified RCU primitives to alloc_fd(), files_fdtable() and
fcheck_files().

Cc: Alexander Viro <viro@...iv.linux.org.uk>
Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
---
 fs/file.c               |    2 +-
 include/linux/fdtable.h |    7 +++++--
 2 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/fs/file.c b/fs/file.c
index f313314..c506bc6 100644
--- a/fs/file.c
+++ b/fs/file.c
@@ -477,7 +477,7 @@ repeat:
 	error = fd;
 #if 1
 	/* Sanity check */
-	if (rcu_dereference(fdt->fd[fd]) != NULL) {
+	if (rcu_dereference_raw(fdt->fd[fd]) != NULL) {
 		printk(KERN_WARNING "alloc_fd: slot %d not NULL!\n", fd);
 		rcu_assign_pointer(fdt->fd[fd], NULL);
 	}
diff --git a/include/linux/fdtable.h b/include/linux/fdtable.h
index a2ec74b..e498a0c 100644
--- a/include/linux/fdtable.h
+++ b/include/linux/fdtable.h
@@ -57,7 +57,10 @@ struct files_struct {
 	struct file * fd_array[NR_OPEN_DEFAULT];
 };
 
-#define files_fdtable(files) (rcu_dereference((files)->fdt))
+#define files_fdtable(files) \
+	(rcu_dereference_check((files)->fdt, \
+			       rcu_read_lock_held() || \
+			       lockdep_is_held(&(files)->file_lock)))
 
 struct file_operations;
 struct vfsmount;
@@ -78,7 +81,7 @@ 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(fdt->fd[fd]);
+		file = rcu_dereference_check(fdt->fd[fd], rcu_read_lock_held() || lockdep_is_held(&files->file_lock));
 	return file;
 }
 
-- 
1.5.2.5

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