kernfs: remove KERNFS_ACTIVE_REF and add kernfs_lockdep()

There currently are two mechanisms gating active ref lockdep
annotations - KERNFS_LOCKDEP flag and KERNFS_ACTIVE_REF type mask.
The former disables lockdep annotations in kernfs_get/put_active()
while the latter disables all of kernfs_deactivate().

While KERNFS_ACTIVE_REF also behaves as an optimization to skip the
deactivation step for non-file nodes, the benefit is marginal and it
needlessly diverges code paths.  Let's drop KERNFS_ACTIVE_REF and use
KERNFS_LOCKDEP in kernfs_deactivate() too.

While at it, add a test helper kernfs_lockdep() to test KERNFS_LOCKDEP
flag so that it's more convenient and the related code can be compiled
out when not enabled.

Signed-off-by: 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 ed62de6cdf8fd2d1fd2caf0a90a36882fad86d55..1c9130a33048664a099398a6b751765535041496 100644 (file)
--- a/fs/kernfs/dir.c
+++ b/fs/kernfs/dir.c
@@ -22,6 +22,15 @@ 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
@@ -138,7 +147,7 @@ struct kernfs_node *kernfs_get_active(struct kernfs_node *kn)
        if (!atomic_inc_unless_negative(&kn->active))
                return NULL;
 
-       if (kn->flags & KERNFS_LOCKDEP)
+       if (kernfs_lockdep(kn))
                rwsem_acquire_read(&kn->dep_map, 0, 1, _RET_IP_);
        return kn;
 }
@@ -158,7 +167,7 @@ void kernfs_put_active(struct kernfs_node *kn)
        if (unlikely(!kn))
                return;
 
-       if (kn->flags & KERNFS_LOCKDEP)
+       if (kernfs_lockdep(kn))
                rwsem_release(&kn->dep_map, 1, _RET_IP_);
        v = atomic_dec_return(&kn->active);
        if (likely(v != KN_DEACTIVATED_BIAS))
@@ -179,21 +188,21 @@ 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 (atomic_read(&kn->active) != KN_DEACTIVATED_BIAS)
-               lock_contended(&kn->dep_map, _RET_IP_);
+       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_);
+       }
 
        wait_event(root->deactivate_waitq,
                   atomic_read(&kn->active) == KN_DEACTIVATED_BIAS);
 
-       lock_acquired(&kn->dep_map, _RET_IP_);
-       rwsem_release(&kn->dep_map, 1, _RET_IP_);
+       if (kernfs_lockdep(kn)) {
+               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 232f1a632383f537363eabda683c851fc0a4c486..42ad32ff22f8ef41361e90cd170051f6d2dd32c9 100644 (file)
--- a/include/linux/kernfs.h
+++ b/include/linux/kernfs.h
@@ -34,7 +34,6 @@ 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 {