kernfs: mark static names with KERNFS_STATIC_NAME

Because sysfs used struct attribute which are supposed to stay
constant, sysfs didn't copy names when creating regular files.  The
specified string for name was supposed to stay constant.  Such
distinction isn't inherent for kernfs.  kernfs_create_file[_ns]()
should be able to take the same @name as kernfs_create_dir[_ns]()

As there can be huge number of sysfs attributes, we still want to be
able to use static names for sysfs attributes.  This patch renames
kernfs_create_file_ns_key() to __kernfs_create_file() and adds
@name_is_static parameter so that the caller can explicitly indicate
that @name can be used without copying.  kernfs is updated to use
KERNFS_STATIC_NAME to distinguish static and copied names.

This patch doesn't introduce any behavior changes.

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

1 files changed, 14 insertions, 13 deletions

diff --git a/include/linux/kernfs.h b/include/linux/kernfs.h
index 0ca2aedfd31b..321ed84ad4ce 100644
--- a/include/linux/kernfs.h
+++ b/include/linux/kernfs.h
@@ -34,7 +34,6 @@ enum kernfs_node_type {
 };
 
 #define KERNFS_TYPE_MASK        0x000f
-#define KERNFS_COPY_NAME        (KERNFS_DIR | KERNFS_LINK)
 #define KERNFS_ACTIVE_REF       KERNFS_FILE
 #define KERNFS_FLAG_MASK        ~KERNFS_TYPE_MASK
 
@@ -44,6 +43,7 @@ enum kernfs_node_flag {
         KERNFS_HAS_SEQ_SHOW     = 0x0040,
         KERNFS_HAS_MMAP         = 0x0080,
         KERNFS_LOCKDEP          = 0x0100,
+        KERNFS_STATIC_NAME      = 0x0200,
 };
 
 /* type-specific structures for kernfs_node union members */
@@ -212,12 +212,13 @@ void kernfs_destroy_root(struct kernfs_root *root);
 struct kernfs_node *kernfs_create_dir_ns(struct kernfs_node *parent,
                                          const char *name, umode_t mode,
                                          void *priv, const void *ns);
-struct kernfs_node *kernfs_create_file_ns_key(struct kernfs_node *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 kernfs_node *__kernfs_create_file(struct kernfs_node *parent,
+                                         const char *name,
+                                         umode_t mode, loff_t size,
+                                         const struct kernfs_ops *ops,
+                                         void *priv, const void *ns,
+                                         bool name_is_static,
+                                         struct lock_class_key *key);
 struct kernfs_node *kernfs_create_link(struct kernfs_node *parent,
                                        const char *name,
                                        struct kernfs_node *target);
@@ -265,10 +266,10 @@ kernfs_create_dir_ns(struct kernfs_node *parent, const char *name,
 { return ERR_PTR(-ENOSYS); }
 
 static inline struct kernfs_node *
-kernfs_create_file_ns_key(struct kernfs_node *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)
+__kernfs_create_file(struct kernfs_node *parent, const char *name,
+                     umode_t mode, loff_t size, const struct kernfs_ops *ops,
+                     void *priv, const void *ns, bool name_is_static,
+                     struct lock_class_key *key)
 { return ERR_PTR(-ENOSYS); }
 
 static inline struct kernfs_node *
@@ -330,8 +331,8 @@ kernfs_create_file_ns(struct kernfs_node *parent, const char *name,
 #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);
+        return __kernfs_create_file(parent, name, mode, size, ops, priv, ns,
+                                    false, key);
 }
 
 static inline struct kernfs_node *