1 files changed, 68 insertions, 61 deletions

diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
index 2193d30156ef..3ac93737174a 100644
--- a/fs/kernfs/dir.c
+++ b/fs/kernfs/dir.c
@@ -106,18 +106,24 @@ static int kernfs_link_sibling(struct kernfs_node *kn)
  *	kernfs_unlink_sibling - unlink kernfs_node from sibling rbtree
  *	@kn: kernfs_node of interest
  *
- *	Unlink @kn from its sibling rbtree which starts from
- *	kn->parent->dir.children.
+ *	Try to unlink @kn from its sibling rbtree which starts from
+ *	kn->parent->dir.children.  Returns %true if @kn was actually
+ *	removed, %false if @kn wasn't on the rbtree.
  *
  *	Locking:
  *	mutex_lock(kernfs_mutex)
  */
-static void kernfs_unlink_sibling(struct kernfs_node *kn)
+static bool kernfs_unlink_sibling(struct kernfs_node *kn)
 {
+	if (RB_EMPTY_NODE(&kn->rb))
+		return false;
+
 	if (kernfs_type(kn) == KERNFS_DIR)
 		kn->parent->dir.subdirs--;
 
 	rb_erase(&kn->rb, &kn->parent->dir.children);
+	RB_CLEAR_NODE(&kn->rb);
+	return true;
 }
 
 /**
@@ -171,26 +177,34 @@ void kernfs_put_active(struct kernfs_node *kn)
  *	kernfs_deactivate - deactivate kernfs_node
  *	@kn: kernfs_node to deactivate
  *
- *	Deny new active references and drain existing ones.
+ *	Deny new active references and drain existing ones.  Mutiple
+ *	removers may invoke this function concurrently on @kn and all will
+ *	return after deactivation and draining are complete.
  */
 static void kernfs_deactivate(struct kernfs_node *kn)
+	__releases(&kernfs_mutex) __acquires(&kernfs_mutex)
 {
 	struct kernfs_root *root = kernfs_root(kn);
 
+	lockdep_assert_held(&kernfs_mutex);
 	BUG_ON(!(kn->flags & KERNFS_REMOVED));
 
 	if (!(kernfs_type(kn) & KERNFS_ACTIVE_REF))
 		return;
 
-	if (kn->flags & KERNFS_LOCKDEP)
-		rwsem_acquire(&kn->dep_map, 0, 0, _RET_IP_);
+	/* only the first invocation on @kn should deactivate it */
+	if (atomic_read(&kn->active) >= 0)
+		atomic_add(KN_DEACTIVATED_BIAS, &kn->active);
 
-	atomic_add(KN_DEACTIVATED_BIAS, &kn->active);
+	mutex_unlock(&kernfs_mutex);
 
-	if ((kn->flags & KERNFS_LOCKDEP) &&
-	    atomic_read(&kn->active) != KN_DEACTIVATED_BIAS)
-		lock_contended(&kn->dep_map, _RET_IP_);
+	if (kn->flags & KERNFS_LOCKDEP) {
+		rwsem_acquire(&kn->dep_map, 0, 0, _RET_IP_);
+		if (atomic_read(&kn->active) != KN_DEACTIVATED_BIAS)
+			lock_contended(&kn->dep_map, _RET_IP_);
+	}
 
+	/* but everyone should wait for draining */
 	wait_event(root->deactivate_waitq,
 		   atomic_read(&kn->active) == KN_DEACTIVATED_BIAS);
 
@@ -198,6 +212,8 @@ static void kernfs_deactivate(struct kernfs_node *kn)
 		lock_acquired(&kn->dep_map, _RET_IP_);
 		rwsem_release(&kn->dep_map, 1, _RET_IP_);
 	}
+
+	mutex_lock(&kernfs_mutex);
 }
 
 /**
@@ -347,6 +363,7 @@ static struct kernfs_node *__kernfs_new_node(struct kernfs_root *root,
 
 	atomic_set(&kn->count, 1);
 	atomic_set(&kn->active, 0);
+	RB_CLEAR_NODE(&kn->rb);
 
 	kn->name = name;
 	kn->mode = mode;
@@ -454,49 +471,6 @@ int kernfs_add_one(struct kernfs_addrm_cxt *acxt, struct kernfs_node *kn)
 }
 
 /**
- *	kernfs_remove_one - remove kernfs_node from parent
- *	@acxt: addrm context to use
- *	@kn: kernfs_node to be removed
- *
- *	Mark @kn removed and drop nlink of parent inode if @kn is a
- *	directory.  @kn is unlinked from the children list.
- *
- *	This function should be called between calls to
- *	kernfs_addrm_start() and kernfs_addrm_finish() and should be
- *	passed the same @acxt as passed to kernfs_addrm_start().
- *
- *	LOCKING:
- *	Determined by kernfs_addrm_start().
- */
-static void kernfs_remove_one(struct kernfs_addrm_cxt *acxt,
-			      struct kernfs_node *kn)
-{
-	struct kernfs_iattrs *ps_iattr;
-
-	/*
-	 * Removal can be called multiple times on the same node.  Only the
-	 * first invocation is effective and puts the base ref.
-	 */
-	if (kn->flags & KERNFS_REMOVED)
-		return;
-
-	if (kn->parent) {
-		kernfs_unlink_sibling(kn);
-
-		/* Update timestamps on the parent */
-		ps_iattr = kn->parent->iattr;
-		if (ps_iattr) {
-			ps_iattr->ia_iattr.ia_ctime = CURRENT_TIME;
-			ps_iattr->ia_iattr.ia_mtime = CURRENT_TIME;
-		}
-	}
-
-	kn->flags |= KERNFS_REMOVED;
-	kn->u.removed_list = acxt->removed;
-	acxt->removed = kn;
-}
-
-/**
  *	kernfs_addrm_finish - finish up kernfs_node add/remove
  *	@acxt: addrm context to finish up
  *
@@ -519,7 +493,6 @@ void kernfs_addrm_finish(struct kernfs_addrm_cxt *acxt)
 
 		acxt->removed = kn->u.removed_list;
 
-		kernfs_deactivate(kn);
 		kernfs_unmap_bin_file(kn);
 		kernfs_put(kn);
 	}
@@ -828,20 +801,54 @@ static struct kernfs_node *kernfs_next_descendant_post(struct kernfs_node *pos,
 static void __kernfs_remove(struct kernfs_addrm_cxt *acxt,
 			    struct kernfs_node *kn)
 {
-	struct kernfs_node *pos, *next;
+	struct kernfs_node *pos;
+
+	lockdep_assert_held(&kernfs_mutex);
 
 	if (!kn)
 		return;
 
 	pr_debug("kernfs %s: removing\n", kn->name);
 
-	next = NULL;
+	/* disable lookup and node creation under @kn */
+	pos = NULL;
+	while ((pos = kernfs_next_descendant_post(pos, kn)))
+		pos->flags |= KERNFS_REMOVED;
+
+	/* deactivate and unlink the subtree node-by-node */
 	do {
-		pos = next;
-		next = kernfs_next_descendant_post(pos, kn);
-		if (pos)
-			kernfs_remove_one(acxt, pos);
-	} while (next);
+		pos = kernfs_leftmost_descendant(kn);
+
+		/*
+		 * kernfs_deactivate() drops kernfs_mutex temporarily and
+		 * @pos's base ref could have been put by someone else by
+		 * the time the function returns.  Make sure it doesn't go
+		 * away underneath us.
+		 */
+		kernfs_get(pos);
+
+		kernfs_deactivate(pos);
+
+		/*
+		 * kernfs_unlink_sibling() succeeds once per node.  Use it
+		 * to decide who's responsible for cleanups.
+		 */
+		if (!pos->parent || kernfs_unlink_sibling(pos)) {
+			struct kernfs_iattrs *ps_iattr =
+				pos->parent ? pos->parent->iattr : NULL;
+
+			/* update timestamps on the parent */
+			if (ps_iattr) {
+				ps_iattr->ia_iattr.ia_ctime = CURRENT_TIME;
+				ps_iattr->ia_iattr.ia_mtime = CURRENT_TIME;
+			}
+
+			pos->u.removed_list = acxt->removed;
+			acxt->removed = pos;
+		}
+
+		kernfs_put(pos);
+	} while (pos != kn);
 }
 
 /**