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, 9 insertions, 7 deletions

diff --git a/fs/sysfs/symlink.c b/fs/sysfs/symlink.c
index 76efeab6db4e..b137aa3a486c 100644
--- a/fs/sysfs/symlink.c
+++ b/fs/sysfs/symlink.c
@@ -44,7 +44,7 @@ struct sysfs_dirent *kernfs_create_link(struct sysfs_dirent *parent,
 	if (parent->s_flags & SYSFS_FLAG_NS)
 		sd->s_ns = target->s_ns;
 	sd->s_symlink.target_sd = target;
-	sysfs_get(target);	/* ref owned by symlink */
+	kernfs_get(target);	/* ref owned by symlink */
 
 	sysfs_addrm_start(&acxt);
 	error = sysfs_add_one(&acxt, sd, parent);
@@ -53,7 +53,7 @@ struct sysfs_dirent *kernfs_create_link(struct sysfs_dirent *parent,
 	if (!error)
 		return sd;
 
-	sysfs_put(sd);
+	kernfs_put(sd);
 	return ERR_PTR(error);
 }
 
@@ -72,15 +72,17 @@ static int sysfs_do_create_link_sd(struct sysfs_dirent *parent_sd,
 	 * sysfs_remove_dir() for details.
 	 */
 	spin_lock(&sysfs_symlink_target_lock);
-	if (target->sd)
-		target_sd = sysfs_get(target->sd);
+	if (target->sd) {
+		target_sd = target->sd;
+		kernfs_get(target_sd);
+	}
 	spin_unlock(&sysfs_symlink_target_lock);
 
 	if (!target_sd)
 		return -ENOENT;
 
 	sd = kernfs_create_link(parent_sd, name, target_sd);
-	sysfs_put(target_sd);
+	kernfs_put(target_sd);
 
 	if (!IS_ERR(sd))
 		return 0;
@@ -216,7 +218,7 @@ int sysfs_rename_link_ns(struct kobject *kobj, struct kobject *targ,
 		old_ns = targ->sd->s_ns;
 
 	result = -ENOENT;
-	sd = sysfs_get_dirent_ns(parent_sd, old, old_ns);
+	sd = kernfs_find_and_get_ns(parent_sd, old, old_ns);
 	if (!sd)
 		goto out;
 
@@ -229,7 +231,7 @@ int sysfs_rename_link_ns(struct kobject *kobj, struct kobject *targ,
 	result = kernfs_rename_ns(sd, parent_sd, new, new_ns);
 
 out:
-	sysfs_put(sd);
+	kernfs_put(sd);
 	return result;
 }
 EXPORT_SYMBOL_GPL(sysfs_rename_link_ns);