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>

diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
index 1c9130a33048664a099398a6b751765535041496..ed62de6cdf8fd2d1fd2caf0a90a36882fad86d55 100644 (file)
--- 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_);
 }
 
 /**

diff --git a/include/linux/kernfs.h b/include/linux/kernfs.h
index 42ad32ff22f8ef41361e90cd170051f6d2dd32c9..232f1a632383f537363eabda683c851fc0a4c486 100644 (file)
--- a/include/linux/kernfs.h
+++ b/include/linux/kernfs.h
@@ -34,6 +34,7 @@ enum kernfs_node_type {
 };
 
 #define KERNFS_TYPE_MASK       0x000f
+#define KERNFS_ACTIVE_REF      KERNFS_FILE
 #define KERNFS_FLAG_MASK       ~KERNFS_TYPE_MASK
 
 enum kernfs_node_flag {