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, 15 insertions, 8 deletions

diff --git a/fs/kernfs/file.c b/fs/kernfs/file.c
index 053cfd9a6a40..316604cc3a1c 100644
--- a/fs/kernfs/file.c
+++ b/fs/kernfs/file.c
@@ -762,7 +762,7 @@ const struct file_operations kernfs_file_fops = {
 };
 
 /**
- * kernfs_create_file_ns_key - create a file
+ * __kernfs_create_file - kernfs internal function to create a file
  * @parent: directory to create the file in
  * @name: name of the file
  * @mode: mode of the file
@@ -770,23 +770,30 @@ const struct file_operations kernfs_file_fops = {
  * @ops: kernfs operations for the file
  * @priv: private data for the file
  * @ns: optional namespace tag of the file
+ * @static_name: don't copy file name
  * @key: lockdep key for the file's active_ref, %NULL to disable lockdep
  *
  * Returns the created node on success, ERR_PTR() value on error.
  */
-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_addrm_cxt acxt;
         struct kernfs_node *kn;
+        unsigned flags;
         int rc;
 
+        flags = KERNFS_FILE;
+        if (name_is_static)
+                flags |= KERNFS_STATIC_NAME;
+
         kn = kernfs_new_node(kernfs_root(parent), name,
-                             (mode & S_IALLUGO) | S_IFREG, KERNFS_FILE);
+                             (mode & S_IALLUGO) | S_IFREG, flags);
         if (!kn)
                 return ERR_PTR(-ENOMEM);