sysfs, kernfs: introduce kernfs[_find_and]_get() and kernfs_put()

Introduce kernfs interface for finding, getting and putting
sysfs_dirents.

* sysfs_find_dirent() is renamed to kernfs_find_ns() and lockdep
  assertion for sysfs_mutex is added.

* sysfs_get_dirent_ns() is renamed to kernfs_find_and_get().

* Macro inline dancing around __sysfs_get/put() are removed and
  kernfs_get/put() are made proper functions implemented in
  fs/sysfs/dir.c.

While the conversions are mostly equivalent, there's one difference -
kernfs_get() doesn't return the input param as its return value.  This
change is intentional.  While passing through the input increases
writability in some areas, it is unnecessary and has been shown to
cause confusion regarding how the last ref is handled.

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

1 files changed, 19 insertions, 0 deletions

diff --git a/include/linux/kernfs.h b/include/linux/kernfs.h
index 105d09dcb064..fd8f574ef2fe 100644
--- a/include/linux/kernfs.h
+++ b/include/linux/kernfs.h
@@ -71,6 +71,11 @@ struct kernfs_ops {
 
 #ifdef CONFIG_SYSFS
 
+struct sysfs_dirent *kernfs_find_and_get_ns(struct sysfs_dirent *parent,
+					    const char *name, const void *ns);
+void kernfs_get(struct sysfs_dirent *sd);
+void kernfs_put(struct sysfs_dirent *sd);
+
 struct sysfs_dirent *kernfs_create_dir_ns(struct sysfs_dirent *parent,
 					  const char *name, void *priv,
 					  const void *ns);
@@ -95,6 +100,14 @@ void kernfs_notify(struct sysfs_dirent *sd);
 #else	/* CONFIG_SYSFS */
 
 static inline struct sysfs_dirent *
+kernfs_find_and_get_ns(struct sysfs_dirent *parent, const char *name,
+		       const void *ns)
+{ return NULL; }
+
+static inline void kernfs_get(struct sysfs_dirent *sd) { }
+static inline void kernfs_put(struct sysfs_dirent *sd) { }
+
+static inline struct sysfs_dirent *
 kernfs_create_dir_ns(struct sysfs_dirent *parent, const char *name, void *priv,
 		     const void *ns)
 { return ERR_PTR(-ENOSYS); }
@@ -133,6 +146,12 @@ static inline void kernfs_notify(struct sysfs_dirent *sd) { }
 #endif	/* CONFIG_SYSFS */
 
 static inline struct sysfs_dirent *
+kernfs_find_and_get(struct sysfs_dirent *sd, const char *name)
+{
+	return kernfs_find_and_get_ns(sd, name, NULL);
+}
+
+static inline struct sysfs_dirent *
 kernfs_create_dir(struct sysfs_dirent *parent, const char *name, void *priv)
 {
 	return kernfs_create_dir_ns(parent, name, priv, NULL);