sysfs, kernfs: revamp sysfs_dirent active_ref lockdep annotation

Currently, sysfs_dirent active_ref lockdep annotation uses
attribute->[s]key as the lockdep key, which forces
kernfs_create_file_ns() to assume that sysfs_dirent->priv is pointing
to a struct attribute which may not be true for non-sysfs users.  This
patch restructures the lockdep annotation such that

* kernfs_ops contains lockdep_key which is used by default for files
  created kernfs_create_file_ns().

* kernfs_create_file_ns_key() is introduced which takes an extra @key
  argument.  The created file will use the specified key for
  active_ref lockdep annotation.  If NULL is specified, lockdep for
  the file is disabled.

* sysfs_add_file_mode_ns() is updated to use
  kernfs_create_file_ns_key() with the appropriate key from the
  attribute or NULL if ignore_lockdep is set.

This makes the lockdep annotation properly contained in kernfs while
allowing sysfs to cleanly keep its current behavior.  This patch
doesn't introduce any behavior differences.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 29 insertions, 8 deletions

diff --git a/include/linux/kernfs.h b/include/linux/kernfs.h
index f20796ecc76e..105d09dcb064 100644
--- a/include/linux/kernfs.h
+++ b/include/linux/kernfs.h
@@ -11,6 +11,7 @@
 #include <linux/err.h>
 #include <linux/list.h>
 #include <linux/mutex.h>
+#include <linux/lockdep.h>
 
 struct file;
 struct iattr;
@@ -62,6 +63,10 @@ struct kernfs_ops {
                          loff_t off);
 
         int (*mmap)(struct sysfs_open_file *of, struct vm_area_struct *vma);
+
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+        struct lock_class_key   lockdep_key;
+#endif
 };
 
 #ifdef CONFIG_SYSFS
@@ -69,11 +74,12 @@ struct kernfs_ops {
 struct sysfs_dirent *kernfs_create_dir_ns(struct sysfs_dirent *parent,
                                           const char *name, void *priv,
                                           const void *ns);
-struct sysfs_dirent *kernfs_create_file_ns(struct sysfs_dirent *parent,
-                                           const char *name,
-                                           umode_t mode, loff_t size,
-                                           const struct kernfs_ops *ops,
-                                           void *priv, const void *ns);
+struct sysfs_dirent *kernfs_create_file_ns_key(struct sysfs_dirent *parent,
+                                               const char *name,
+                                               umode_t mode, loff_t size,
+                                               const struct kernfs_ops *ops,
+                                               void *priv, const void *ns,
+                                               struct lock_class_key *key);
 struct sysfs_dirent *kernfs_create_link(struct sysfs_dirent *parent,
                                         const char *name,
                                         struct sysfs_dirent *target);
@@ -94,9 +100,10 @@ kernfs_create_dir_ns(struct sysfs_dirent *parent, const char *name, void *priv,
 { return ERR_PTR(-ENOSYS); }
 
 static inline struct sysfs_dirent *
-kernfs_create_file_ns(struct sysfs_dirent *parent, const char *name,
-                      umode_t mode, loff_t size, const struct kernfs_ops *ops,
-                      void *priv, const void *ns)
+kernfs_create_file_ns_key(struct sysfs_dirent *parent, const char *name,
+                          umode_t mode, loff_t size,
+                          const struct kernfs_ops *ops, void *priv,
+                          const void *ns, struct lock_class_key *key)
 { return ERR_PTR(-ENOSYS); }
 
 static inline struct sysfs_dirent *
@@ -132,6 +139,20 @@ kernfs_create_dir(struct sysfs_dirent *parent, const char *name, void *priv)
 }
 
 static inline struct sysfs_dirent *
+kernfs_create_file_ns(struct sysfs_dirent *parent, const char *name,
+                      umode_t mode, loff_t size, const struct kernfs_ops *ops,
+                      void *priv, const void *ns)
+{
+        struct lock_class_key *key = NULL;
+
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+        key = (struct lock_class_key *)&ops->lockdep_key;
+#endif
+        return kernfs_create_file_ns_key(parent, name, mode, size, ops, priv,
+                                         ns, key);
+}
+
+static inline struct sysfs_dirent *
 kernfs_create_file(struct sysfs_dirent *parent, const char *name, umode_t mode,
                    loff_t size, const struct kernfs_ops *ops, void *priv)
 {