Revert "fsnotify: clear PARENT_WATCHED flags lazily"

This reverts commit 887fdf24d2.

fs/notify/fsnotify.c

@@ -103,13 +103,17 @@ void fsnotify_sb_delete(struct super_block *sb)
  * parent cares.  Thus when an event happens on a child it can quickly tell
  * if there is a need to find a parent and send the event to the parent.
  */
-void fsnotify_set_children_dentry_flags(struct inode *inode)
+void __fsnotify_update_child_dentry_flags(struct inode *inode)
 {
 	struct dentry *alias;
+	int watched;
 
 	if (!S_ISDIR(inode->i_mode))
 		return;
 
+	/* determine if the children should tell inode about their events */
+	watched = fsnotify_inode_watches_children(inode);
+
 	spin_lock(&inode->i_lock);
 	/* run all of the dentries associated with this inode.  Since this is a
 	 * directory, there damn well better only be one item on this list */
@@ -125,7 +129,10 @@ void fsnotify_set_children_dentry_flags(struct inode *inode)
 				continue;
 
 			spin_lock_nested(&child->d_lock, DENTRY_D_LOCK_NESTED);
+			if (watched)
 				child->d_flags |= DCACHE_FSNOTIFY_PARENT_WATCHED;
+			else
+				child->d_flags &= ~DCACHE_FSNOTIFY_PARENT_WATCHED;
 			spin_unlock(&child->d_lock);
 		}
 		spin_unlock(&alias->d_lock);
@@ -133,24 +140,6 @@ void fsnotify_set_children_dentry_flags(struct inode *inode)
 	spin_unlock(&inode->i_lock);
 }
 
-/*
- * Lazily clear false positive PARENT_WATCHED flag for child whose parent had
- * stopped watching children.
- */
-static void fsnotify_clear_child_dentry_flag(struct inode *pinode,
-					     struct dentry *dentry)
-{
-	spin_lock(&dentry->d_lock);
-	/*
-	 * d_lock is a sufficient barrier to prevent observing a non-watched
-	 * parent state from before the fsnotify_set_children_dentry_flags()
-	 * or fsnotify_update_flags() call that had set PARENT_WATCHED.
-	 */
-	if (!fsnotify_inode_watches_children(pinode))
-		dentry->d_flags &= ~DCACHE_FSNOTIFY_PARENT_WATCHED;
-	spin_unlock(&dentry->d_lock);
-}
-
 /* Are inode/sb/mount interested in parent and name info with this event? */
 static bool fsnotify_event_needs_parent(struct inode *inode, struct mount *mnt,
 					__u32 mask)
@@ -219,7 +208,7 @@ int __fsnotify_parent(struct dentry *dentry, __u32 mask, const void *data,
 	p_inode = parent->d_inode;
 	p_mask = fsnotify_inode_watches_children(p_inode);
 	if (unlikely(parent_watched && !p_mask))
-		fsnotify_clear_child_dentry_flag(p_inode, dentry);
+		__fsnotify_update_child_dentry_flags(p_inode);
 
 	/*
 	 * Include parent/name in notification either if some notification

fs/notify/fsnotify.h

@@ -74,7 +74,7 @@ static inline void fsnotify_clear_marks_by_sb(struct super_block *sb)
  * update the dentry->d_flags of all of inode's children to indicate if inode cares
  * about events that happen to its children.
  */
-extern void fsnotify_set_children_dentry_flags(struct inode *inode);
+extern void __fsnotify_update_child_dentry_flags(struct inode *inode);
 
 extern struct kmem_cache *fsnotify_mark_connector_cachep;
 

fs/notify/mark.c

@@ -176,24 +176,6 @@ static void *__fsnotify_recalc_mask(struct fsnotify_mark_connector *conn)
 	return fsnotify_update_iref(conn, want_iref);
 }
 
-static bool fsnotify_conn_watches_children(
-					struct fsnotify_mark_connector *conn)
-{
-	if (conn->type != FSNOTIFY_OBJ_TYPE_INODE)
-		return false;
-
-	return fsnotify_inode_watches_children(fsnotify_conn_inode(conn));
-}
-
-static void fsnotify_conn_set_children_dentry_flags(
-					struct fsnotify_mark_connector *conn)
-{
-	if (conn->type != FSNOTIFY_OBJ_TYPE_INODE)
-		return;
-
-	fsnotify_set_children_dentry_flags(fsnotify_conn_inode(conn));
-}
-
 /*
  * Calculate mask of events for a list of marks. The caller must make sure
  * connector and connector->obj cannot disappear under us.  Callers achieve
@@ -202,23 +184,15 @@ static void fsnotify_conn_set_children_dentry_flags(
  */
 void fsnotify_recalc_mask(struct fsnotify_mark_connector *conn)
 {
-	bool update_children;
-
 	if (!conn)
 		return;
 
 	spin_lock(&conn->lock);
-	update_children = !fsnotify_conn_watches_children(conn);
 	__fsnotify_recalc_mask(conn);
-	update_children &= fsnotify_conn_watches_children(conn);
 	spin_unlock(&conn->lock);
-	/*
+	if (conn->type == FSNOTIFY_OBJ_TYPE_INODE)
-	 * Set children's PARENT_WATCHED flags only if parent started watching.
+		__fsnotify_update_child_dentry_flags(
-	 * When parent stops watching, we clear false positive PARENT_WATCHED
+					fsnotify_conn_inode(conn));
-	 * flags lazily in __fsnotify_parent().
-	 */
-	if (update_children)
-		fsnotify_conn_set_children_dentry_flags(conn);
 }
 
 /* Free all connectors queued for freeing once SRCU period ends */

include/linux/fsnotify_backend.h

@@ -563,14 +563,12 @@ static inline __u32 fsnotify_parent_needed_mask(__u32 mask)
 
 static inline int fsnotify_inode_watches_children(struct inode *inode)
 {
-	__u32 parent_mask = READ_ONCE(inode->i_fsnotify_mask);
-
 	/* FS_EVENT_ON_CHILD is set if the inode may care */
-	if (!(parent_mask & FS_EVENT_ON_CHILD))
+	if (!(inode->i_fsnotify_mask & FS_EVENT_ON_CHILD))
 		return 0;
 	/* this inode might care about child events, does it care about the
 	 * specific set of events that can happen on a child? */
-	return parent_mask & FS_EVENTS_POSS_ON_CHILD;
+	return inode->i_fsnotify_mask & FS_EVENTS_POSS_ON_CHILD;
 }
 
 /*
@@ -584,7 +582,7 @@ static inline void fsnotify_update_flags(struct dentry *dentry)
 	/*
 	 * Serialisation of setting PARENT_WATCHED on the dentries is provided
 	 * by d_lock. If inotify_inode_watched changes after we have taken
-	 * d_lock, the following fsnotify_set_children_dentry_flags call will
+	 * d_lock, the following __fsnotify_update_child_dentry_flags call will
 	 * find our entry, so it will spin until we complete here, and update
 	 * us with the new state.
 	 */