fsnotify: store struct file not struct path

Al explains that calling dentry_open() with a mnt/dentry pair is only
garunteed to be safe if they are already used in an open struct file.  To
make sure this is the case don't store and use a struct path in fsnotify,
always use a struct file.

Signed-off-by: Eric Paris <eparis@redhat.com>
diff --git a/fs/notify/fsnotify.c b/fs/notify/fsnotify.c
index 72aae40..4788c86 100644
--- a/fs/notify/fsnotify.c
+++ b/fs/notify/fsnotify.c
@@ -84,7 +84,7 @@
 }
 
 /* Notify this dentry's parent about a child's events. */
-void __fsnotify_parent(struct path *path, struct dentry *dentry, __u32 mask)
+void __fsnotify_parent(struct file *file, struct dentry *dentry, __u32 mask)
 {
 	struct dentry *parent;
 	struct inode *p_inode;
@@ -92,7 +92,7 @@
 	bool should_update_children = false;
 
 	if (!dentry)
-		dentry = path->dentry;
+		dentry = file->f_path.dentry;
 
 	if (!(dentry->d_flags & DCACHE_FSNOTIFY_PARENT_WATCHED))
 		return;
@@ -124,8 +124,8 @@
 		 * specifies these are events which came from a child. */
 		mask |= FS_EVENT_ON_CHILD;
 
-		if (path)
-			fsnotify(p_inode, mask, path, FSNOTIFY_EVENT_PATH,
+		if (file)
+			fsnotify(p_inode, mask, file, FSNOTIFY_EVENT_FILE,
 				 dentry->d_name.name, 0);
 		else
 			fsnotify(p_inode, mask, dentry->d_inode, FSNOTIFY_EVENT_INODE,
@@ -154,10 +154,10 @@
 		spin_unlock(&inode->i_lock);
 	}
 
-	if (data_is == FSNOTIFY_EVENT_PATH) {
+	if (data_is == FSNOTIFY_EVENT_FILE) {
 		struct vfsmount *mnt;
 
-		mnt = ((struct path *)data)->mnt;
+		mnt = ((struct file *)data)->f_path.mnt;
 		if (mnt && !hlist_empty(&mnt->mnt_fsnotify_marks)) {
 			spin_lock(&mnt->mnt_root->d_lock);
 			hlist_for_each_entry(mark, node, &mnt->mnt_fsnotify_marks, m.m_list) {
@@ -228,8 +228,8 @@
 	    !(test_mask & fsnotify_vfsmount_mask))
 		return 0;
  
-	if (data_is == FSNOTIFY_EVENT_PATH)
-		mnt = ((struct path *)data)->mnt;
+	if (data_is == FSNOTIFY_EVENT_FILE)
+		mnt = ((struct file *)data)->f_path.mnt;
 
 	/* if this inode's directed listeners don't care and nothing on the vfsmount
 	 * listeners list cares, nothing to do */