Revert "kernfs: remove KERNFS_ACTIVE_REF and add kernfs_lockdep()"

This reverts commit a69d001cfc712b96ec9d7ba44d6285702a38dabf.

Tejun writes:
        I'm sorry but can you please revert the whole series?
        get_active() waiting while a node is deactivated has potential
        to lead to deadlock and that deactivate/reactivate interface is
        something fundamentally flawed and that cgroup will have to work
        with the remove_self() like everybody else.  IOW, I think the
        first posting was correct.

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

1 files changed, 11 insertions, 20 deletions

diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
index 1c9130a33048..ed62de6cdf8f 100644
--- a/fs/kernfs/dir.c
+++ b/fs/kernfs/dir.c
@@ -22,15 +22,6 @@ DEFINE_MUTEX(kernfs_mutex);
 
 #define rb_to_kn(X) rb_entry((X), struct kernfs_node, rb)
 
-static bool kernfs_lockdep(struct kernfs_node *kn)
-{
-#ifdef CONFIG_DEBUG_LOCK_ALLOC
-        return kn->flags & KERNFS_LOCKDEP;
-#else
-        return false;
-#endif
-}
-
 /**
  *      kernfs_name_hash
  *      @name: Null terminated string to hash
@@ -147,7 +138,7 @@ struct kernfs_node *kernfs_get_active(struct kernfs_node *kn)
         if (!atomic_inc_unless_negative(&kn->active))
                 return NULL;
 
-        if (kernfs_lockdep(kn))
+        if (kn->flags & KERNFS_LOCKDEP)
                 rwsem_acquire_read(&kn->dep_map, 0, 1, _RET_IP_);
         return kn;
 }
@@ -167,7 +158,7 @@ void kernfs_put_active(struct kernfs_node *kn)
         if (unlikely(!kn))
                 return;
 
-        if (kernfs_lockdep(kn))
+        if (kn->flags & KERNFS_LOCKDEP)
                 rwsem_release(&kn->dep_map, 1, _RET_IP_);
         v = atomic_dec_return(&kn->active);
         if (likely(v != KN_DEACTIVATED_BIAS))
@@ -188,21 +179,21 @@ static void kernfs_deactivate(struct kernfs_node *kn)
 
         BUG_ON(!(kn->flags & KERNFS_REMOVED));
 
+        if (!(kernfs_type(kn) & KERNFS_ACTIVE_REF))
+                return;
+
+        rwsem_acquire(&kn->dep_map, 0, 0, _RET_IP_);
+
         atomic_add(KN_DEACTIVATED_BIAS, &kn->active);
 
-        if (kernfs_lockdep(kn)) {
-                rwsem_acquire(&kn->dep_map, 0, 0, _RET_IP_);
-                if (atomic_read(&kn->active) != KN_DEACTIVATED_BIAS)
-                        lock_contended(&kn->dep_map, _RET_IP_);
-        }
+        if (atomic_read(&kn->active) != KN_DEACTIVATED_BIAS)
+                lock_contended(&kn->dep_map, _RET_IP_);
 
         wait_event(root->deactivate_waitq,
                    atomic_read(&kn->active) == KN_DEACTIVATED_BIAS);
 
-        if (kernfs_lockdep(kn)) {
-                lock_acquired(&kn->dep_map, _RET_IP_);
-                rwsem_release(&kn->dep_map, 1, _RET_IP_);
-        }
+        lock_acquired(&kn->dep_map, _RET_IP_);
+        rwsem_release(&kn->dep_map, 1, _RET_IP_);
 }
 
 /**