NodeMonitor: Resolve mount points for B_WATCH_CHILDREN.

* When a watched directory contains a mount point, we need to resolve
  the actual parent directory of the mount point in the file system to
  serve the monitor.

headers/private/kernel/vfs.h

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2015, Axel Dörfler, [email protected].
+ * Copyright 2002-2016, Axel Dörfler, [email protected].
  * Distributed under the terms of the MIT License.
  *
  * Copyright 2001-2002, Travis Geiselbrecht. All rights reserved.
@@ -126,6 +126,8 @@ status_t	vfs_get_cwd(dev_t *_mountID, ino_t *_vnodeID);
 void		vfs_unlock_vnode_if_locked(struct file_descriptor *descriptor);
 status_t	vfs_unmount(dev_t mountID, uint32 flags);
 status_t	vfs_disconnect_vnode(dev_t mountID, ino_t vnodeID);
+status_t	vfs_resolve_parent(struct vnode* parent, dev_t* device,
+				ino_t* node);
 void		vfs_free_unused_vnodes(int32 level);
 
 status_t	vfs_read_stat(int fd, const char *path, bool traverseLeafLink,

src/system/kernel/fs/node_monitor.cpp

@@ -26,6 +26,7 @@
 #include <util/list.h>
 
 #include "node_monitor_private.h"
+#include "Vnode.h"
 
 
 //#define TRACE_MONITOR
@@ -153,6 +154,8 @@ class NodeMonitorService : public NotificationService {
 		status_t _SendNotificationMessage(KMessage &message,
 			interested_monitor_listener_list *interestedListeners,
 			int32 interestedListenerCount);
+		void _ResolveMountPoint(dev_t device, ino_t directory,
+			dev_t& parentDevice, ino_t& parentDirectory);
 
 		struct monitor_hash_key {
 			dev_t	device;
@@ -623,6 +626,25 @@ NodeMonitorService::_SendNotificationMessage(KMessage &message,
 }
 
 
+/*!	\brief Resolves the device/directory node pair to the node it's covered
+	by, if any.
+*/
+void
+NodeMonitorService::_ResolveMountPoint(dev_t device, ino_t directory,
+	dev_t& parentDevice, ino_t& parentDirectory)
+{
+	struct vnode* vnode;
+	status_t status = vfs_get_vnode(device, directory, true, &vnode);
+	if (status == B_OK) {
+		if (vnode->covers != NULL)
+			status = vfs_resolve_parent(vnode, &parentDevice, &parentDirectory);
+		vfs_put_vnode(vnode);
+	}
+	if (status != B_OK)
+		dprintf("Resolving mount point %ld:%lld failed!\n", device, directory);
+}
+
+
 /*!	\brief Notifies all interested listeners that an entry has been created
 		   or removed.
 	\param opcode \c B_ENTRY_CREATED or \c B_ENTRY_REMOVED.
@@ -747,8 +769,15 @@ NodeMonitorService::NotifyStatChanged(dev_t device, ino_t directory, ino_t node,
 	_GetInterestedVolumeListeners(device, watchFlag, interestedListeners,
 		interestedListenerCount);
 	// ... for the directory
-	if (directory >= 0) {
+	if (directory > 0) {
-		_GetInterestedMonitorListeners(device, directory,
+		dev_t parentDevice = device;
+		ino_t parentDirectory = directory;
+		if (directory == node) {
+			// This is a mount point -- get its file system parent
+			_ResolveMountPoint(device, directory, parentDevice,
+				parentDirectory);
+		}
+		_GetInterestedMonitorListeners(parentDevice, parentDirectory,
 			B_WATCH_CHILDREN | watchFlag,
 			interestedListeners, interestedListenerCount);
 	}
@@ -799,8 +828,15 @@ NodeMonitorService::NotifyAttributeChanged(dev_t device, ino_t directory,
 	_GetInterestedVolumeListeners(device, B_WATCH_ATTR,
 		interestedListeners, interestedListenerCount);
 	// ... for the directory
-	if (directory >= 0) {
+	if (directory > 0) {
-		_GetInterestedMonitorListeners(device, directory,
+		dev_t parentDevice = device;
+		ino_t parentDirectory = directory;
+		if (directory == node) {
+			// This is a mount point -- get its file system parent
+			_ResolveMountPoint(device, directory, parentDevice,
+				parentDirectory);
+		}
+		_GetInterestedMonitorListeners(parentDevice, parentDirectory,
 			B_WATCH_CHILDREN | B_WATCH_ATTR,
 			interestedListeners, interestedListenerCount);
 	}

src/system/kernel/fs/vfs.cpp

@@ -1,6 +1,6 @@
 /*
  * Copyright 2005-2013, Ingo Weinhold, ingo_weinhold@gmx.de.
- * Copyright 2002-2015, Axel Dörfler, axeld@pinc-software.de.
+ * Copyright 2002-2016, Axel Dörfler, axeld@pinc-software.de.
  * Distributed under the terms of the MIT License.
  *
  * Copyright 2001-2002, Travis Geiselbrecht. All rights reserved.
@@ -2914,6 +2914,34 @@ normalize_path(char* path, size_t pathSize, bool traverseLink, bool kernel)
 }
 
 
+static status_t
+resolve_covered_parent(struct vnode* parent, dev_t* _device, ino_t* _node,
+	struct io_context* ioContext)
+{
+	// Make sure the IO context root is not bypassed.
+	if (parent == ioContext->root) {
+		*_device = parent->device;
+		*_node = parent->id;
+		return B_OK;
+	}
+
+	inc_vnode_ref_count(parent);
+		// vnode_path_to_vnode() puts the node
+
+	// ".." is guaranteed not to be clobbered by this call
+	struct vnode* vnode;
+	status_t status = vnode_path_to_vnode(parent, (char*)"..", false, 0,
+		ioContext, &vnode, NULL);
+	if (status == B_OK) {
+		*_device = vnode->device;
+		*_node = vnode->id;
+		put_vnode(vnode);
+	}
+
+	return status;
+}
+
+
 #ifdef ADD_DEBUGGER_COMMANDS
 
 
@@ -4425,6 +4453,19 @@ vfs_normalize_path(const char* path, char* buffer, size_t bufferSize,
 }
 
 
+/*!	\brief Gets the parent of the passed in node.
+
+	Gets the parent of the passed in node, and correctly resolves covered
+	nodes.
+*/
+extern "C" status_t
+vfs_resolve_parent(struct vnode* parent, dev_t* device, ino_t* node)
+{
+	return resolve_covered_parent(parent, device, node,
+		get_current_io_context(true));
+}
+
+
 /*!	\brief Creates a special node in the file system.
 
 	The caller gets a reference to the newly created node (which is passed
@@ -5863,26 +5904,10 @@ fix_dirent(struct vnode* parent, struct dirent* entry,
 	// If this is the ".." entry and the directory covering another vnode,
 	// we need to replace d_dev and d_ino with the actual values.
 	if (strcmp(entry->d_name, "..") == 0 && parent->IsCovering()) {
-		// Make sure the IO context root is not bypassed.
+		return resolve_covered_parent(parent, &entry->d_dev, &entry->d_ino,
-		if (parent == ioContext->root) {
+			ioContext);
-			entry->d_dev = parent->device;
-			entry->d_ino = parent->id;
-		} else {
-			inc_vnode_ref_count(parent);
-				// vnode_path_to_vnode() puts the node
-
-			// ".." is guaranteed not to be clobbered by this call
-			struct vnode* vnode;
-			status_t status = vnode_path_to_vnode(parent, (char*)"..", false, 0,
-				ioContext, &vnode, NULL);
-
-			if (status == B_OK) {
-				entry->d_dev = vnode->device;
-				entry->d_ino = vnode->id;
-				put_vnode(vnode);
 	}
-		}
+
-	} else {
 	// resolve covered vnodes
 	ReadLocker _(&sVnodeLock);
 
@@ -5895,7 +5920,6 @@ fix_dirent(struct vnode* parent, struct dirent* entry,
 		entry->d_dev = vnode->device;
 		entry->d_ino = vnode->id;
 	}
-	}
 
 	return B_OK;
 }