Revert "kernfs: make kernfs_get_active() block if the node is deactivated but not removed"

This reverts commit 895a068a524e134900b9d98b519309b7aae7bbb1.

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, 4 insertions, 21 deletions

diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
index 37dd6408f5f6..770d687ee9f3 100644
--- a/fs/kernfs/dir.c
+++ b/fs/kernfs/dir.c
@@ -149,25 +149,12 @@ struct kernfs_node *kernfs_get_active(struct kernfs_node *kn)
         if (unlikely(!kn))
                 return NULL;
 
-        if (kernfs_lockdep(kn))
-                rwsem_acquire_read(&kn->dep_map, 0, 1, _RET_IP_);
-
-        /*
-         * Try to obtain an active ref.  If @kn is deactivated, we block
-         * till either it's reactivated or killed.
-         */
-        do {
-                if (atomic_inc_unless_negative(&kn->active))
-                        return kn;
-
-                wait_event(kernfs_root(kn)->deactivate_waitq,
-                           atomic_read(&kn->active) >= 0 ||
-                           RB_EMPTY_NODE(&kn->rb));
-        } while (!RB_EMPTY_NODE(&kn->rb));
+        if (!atomic_inc_unless_negative(&kn->active))
+                return NULL;
 
         if (kernfs_lockdep(kn))
-                rwsem_release(&kn->dep_map, 1, _RET_IP_);
-        return NULL;
+                rwsem_acquire_read(&kn->dep_map, 0, 1, _RET_IP_);
+        return kn;
 }
 
 /**
@@ -799,7 +786,6 @@ static void __kernfs_deactivate(struct kernfs_node *kn)
 
 static void __kernfs_remove(struct kernfs_node *kn)
 {
-        struct kernfs_root *root = kernfs_root(kn);
         struct kernfs_node *pos;
 
         lockdep_assert_held(&kernfs_mutex);
@@ -851,9 +837,6 @@ static void __kernfs_remove(struct kernfs_node *kn)
 
                 kernfs_put(pos);
         } while (pos != kn);
-
-        /* some nodes killed, kick get_active waiters */
-        wake_up_all(&root->deactivate_waitq);
 }
 
 /**