[PATCH] lockdep: annotate i_mutex

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>

drivers/usb/core/inode.c

@@ -200,7 +200,7 @@ static void update_sb(struct super_block *sb)
 	if (!root)
 		return;
 
-	mutex_lock(&root->d_inode->i_mutex);
+	mutex_lock_nested(&root->d_inode->i_mutex, I_MUTEX_PARENT);
 
 	list_for_each_entry(bus, &root->d_subdirs, d_u.d_child) {
 		if (bus->d_inode) {

fs/namei.c

@@ -1423,30 +1423,30 @@ struct dentry *lock_rename(struct dentry *p1, struct dentry *p2)
 	struct dentry *p;
 
 	if (p1 == p2) {
-		mutex_lock(&p1->d_inode->i_mutex);
+		mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);
 		return NULL;
 	}
 
 	mutex_lock(&p1->d_inode->i_sb->s_vfs_rename_mutex);
 
 	for (p = p1; p->d_parent != p; p = p->d_parent) {
 		if (p->d_parent == p2) {
-			mutex_lock(&p2->d_inode->i_mutex);
-			mutex_lock(&p1->d_inode->i_mutex);
+			mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_PARENT);
+			mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_CHILD);
 			return p;
 		}
 	}
 
 	for (p = p2; p->d_parent != p; p = p->d_parent) {
 		if (p->d_parent == p1) {
-			mutex_lock(&p1->d_inode->i_mutex);
-			mutex_lock(&p2->d_inode->i_mutex);
+			mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);
+			mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_CHILD);
 			return p;
 		}
 	}
 
-	mutex_lock(&p1->d_inode->i_mutex);
-	mutex_lock(&p2->d_inode->i_mutex);
+	mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);
+	mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_CHILD);
 	return NULL;
 }
 
@@ -1751,7 +1751,7 @@ struct dentry *lookup_create(struct nameidata *nd, int is_dir)
 {
 	struct dentry *dentry = ERR_PTR(-EEXIST);
 
-	mutex_lock(&nd->dentry->d_inode->i_mutex);
+	mutex_lock_nested(&nd->dentry->d_inode->i_mutex, I_MUTEX_PARENT);
 	/*
 	 * Yucky last component or no last component at all?
 	 * (foo/., foo/.., /////)
@@ -2008,7 +2008,7 @@ static long do_rmdir(int dfd, const char __user *pathname)
 			error = -EBUSY;
 			goto exit1;
 	}
-	mutex_lock(&nd.dentry->d_inode->i_mutex);
+	mutex_lock_nested(&nd.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
 	dentry = lookup_hash(&nd);
 	error = PTR_ERR(dentry);
 	if (!IS_ERR(dentry)) {
@@ -2082,7 +2082,7 @@ static long do_unlinkat(int dfd, const char __user *pathname)
 	error = -EISDIR;
 	if (nd.last_type != LAST_NORM)
 		goto exit1;
-	mutex_lock(&nd.dentry->d_inode->i_mutex);
+	mutex_lock_nested(&nd.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
 	dentry = lookup_hash(&nd);
 	error = PTR_ERR(dentry);
 	if (!IS_ERR(dentry)) {

include/linux/fs.h

@@ -542,6 +542,25 @@ struct inode {
 #endif
 };
 
+/*
+ * inode->i_mutex nesting subclasses for the lock validator:
+ *
+ * 0: the object of the current VFS operation
+ * 1: parent
+ * 2: child/target
+ * 3: quota file
+ *
+ * The locking order between these classes is
+ * parent -> child -> normal -> quota
+ */
+enum inode_i_mutex_lock_class
+{
+	I_MUTEX_NORMAL,
+	I_MUTEX_PARENT,
+	I_MUTEX_CHILD,
+	I_MUTEX_QUOTA
+};
+
 /*
  * NOTE: in a 32bit arch with a preemptable kernel and
  * an UP compile the i_size_read/write must be atomic