[PATCH] lockdep: annotate dcache

Teach special (recursive) locking code to the lock validator.  Has no effect
on non-lockdep kernels.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

fs/dcache.c

diff --git a/fs/dcache.c b/fs/dcache.c
index bec4de1..1b4a3a3 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -1339,10 +1339,10 @@
 	 */
 	if (target < dentry) {
 		spin_lock(&target->d_lock);
-		spin_lock(&dentry->d_lock);
+		spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
 	} else {
 		spin_lock(&dentry->d_lock);
-		spin_lock(&target->d_lock);
+		spin_lock_nested(&target->d_lock, DENTRY_D_LOCK_NESTED);
 	}
 
 	/* Move the dentry to the target hash queue, if on different bucket */

include/linux/dcache.h

diff --git a/include/linux/dcache.h b/include/linux/dcache.h
index 0dd1610..471781ffe 100644
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -114,6 +114,18 @@
 	unsigned char d_iname[DNAME_INLINE_LEN_MIN];	/* small names */
 };
 
+/*
+ * dentry->d_lock spinlock nesting subclasses:
+ *
+ * 0: normal
+ * 1: nested
+ */
+enum dentry_d_lock_class
+{
+	DENTRY_D_LOCK_NORMAL, /* implicitly used by plain spin_lock() APIs. */
+	DENTRY_D_LOCK_NESTED
+};
+
 struct dentry_operations {
 	int (*d_revalidate)(struct dentry *, struct nameidata *);
 	int (*d_hash) (struct dentry *, struct qstr *);