kernfs: remove kernfs_addrm_cxt

kernfs_addrm_cxt and the accompanying kernfs_addrm_start/finish() were
added because there were operations which should be performed outside
kernfs_mutex after adding and removing kernfs_nodes.  The necessary
operations were recorded in kernfs_addrm_cxt and performed by
kernfs_addrm_finish(); however, after the recent changes which
relocated deactivation and unmapping so that they're performed
directly during removal, the only operation kernfs_addrm_finish()
performs is kernfs_put(), which can be moved inside the removal path
too.

This patch moves the kernfs_put() of the base ref to __kernfs_remove()
and remove kernfs_addrm_cxt and kernfs_addrm_start/finish().

* kernfs_add_one() is updated to grab and release the parent's active
  ref and kernfs_mutex itself.  kernfs_get/put_active() and
  kernfs_addrm_start/finish() invocations around it are removed from
  all users.

* __kernfs_remove() puts an unlinked node directly instead of chaining
  it to kernfs_addrm_cxt.  Its callers are updated to grab and release
  kernfs_mutex instead of calling kernfs_addrm_start/finish() around
  it.

v2: Updated to fit the v2 restructuring of removal path.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/fs/kernfs/file.c b/fs/kernfs/file.c
index 404ffd2..ffe1beb 100644
--- a/fs/kernfs/file.c
+++ b/fs/kernfs/file.c
@@ -817,7 +817,6 @@
 					 bool name_is_static,
 					 struct lock_class_key *key)
 {
-	struct kernfs_addrm_cxt acxt;
 	struct kernfs_node *kn;
 	unsigned flags;
 	int rc;
@@ -853,14 +852,7 @@
 	if (ops->mmap)
 		kn->flags |= KERNFS_HAS_MMAP;
 
-	rc = -ENOENT;
-	if (kernfs_get_active(parent)) {
-		kernfs_addrm_start(&acxt);
-		rc = kernfs_add_one(&acxt, kn, parent);
-		kernfs_addrm_finish(&acxt);
-		kernfs_put_active(parent);
-	}
-
+	rc = kernfs_add_one(kn, parent);
 	if (rc) {
 		kernfs_put(kn);
 		return ERR_PTR(rc);