Update Linux to v5.4.2

Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/fs/kernfs/file.c b/fs/kernfs/file.c
index dbf5bc2..e8c792b 100644
--- a/fs/kernfs/file.c
+++ b/fs/kernfs/file.c
@@ -1,11 +1,10 @@
+// SPDX-License-Identifier: GPL-2.0-only
 /*
  * fs/kernfs/file.c - kernfs file implementation
  *
  * Copyright (c) 2001-3 Patrick Mochel
  * Copyright (c) 2007 SUSE Linux Products GmbH
  * Copyright (c) 2007, 2013 Tejun Heo <tj@kernel.org>
- *
- * This file is released under the GPLv2.
  */
 
 #include <linux/fs.h>
@@ -832,32 +831,40 @@
  * to see if it supports poll (Neither 'poll' nor 'select' return
  * an appropriate error code).  When in doubt, set a suitable timeout value.
  */
+__poll_t kernfs_generic_poll(struct kernfs_open_file *of, poll_table *wait)
+{
+	struct kernfs_node *kn = kernfs_dentry_node(of->file->f_path.dentry);
+	struct kernfs_open_node *on = kn->attr.open;
+
+	poll_wait(of->file, &on->poll, wait);
+
+	if (of->event != atomic_read(&on->event))
+		return DEFAULT_POLLMASK|EPOLLERR|EPOLLPRI;
+
+	return DEFAULT_POLLMASK;
+}
+
 static __poll_t kernfs_fop_poll(struct file *filp, poll_table *wait)
 {
 	struct kernfs_open_file *of = kernfs_of(filp);
 	struct kernfs_node *kn = kernfs_dentry_node(filp->f_path.dentry);
-	struct kernfs_open_node *on = kn->attr.open;
+	__poll_t ret;
 
 	if (!kernfs_get_active(kn))
-		goto trigger;
+		return DEFAULT_POLLMASK|EPOLLERR|EPOLLPRI;
 
-	poll_wait(filp, &on->poll, wait);
+	if (kn->attr.ops->poll)
+		ret = kn->attr.ops->poll(of, wait);
+	else
+		ret = kernfs_generic_poll(of, wait);
 
 	kernfs_put_active(kn);
-
-	if (of->event != atomic_read(&on->event))
-		goto trigger;
-
-	return DEFAULT_POLLMASK;
-
- trigger:
-	return DEFAULT_POLLMASK|EPOLLERR|EPOLLPRI;
+	return ret;
 }
 
 static void kernfs_notify_workfn(struct work_struct *work)
 {
 	struct kernfs_node *kn;
-	struct kernfs_open_node *on;
 	struct kernfs_super_info *info;
 repeat:
 	/* pop one off the notify_list */
@@ -871,23 +878,13 @@
 	kn->attr.notify_next = NULL;
 	spin_unlock_irq(&kernfs_notify_lock);
 
-	/* kick poll */
-	spin_lock_irq(&kernfs_open_node_lock);
-
-	on = kn->attr.open;
-	if (on) {
-		atomic_inc(&on->event);
-		wake_up_interruptible(&on->poll);
-	}
-
-	spin_unlock_irq(&kernfs_open_node_lock);
-
 	/* kick fsnotify */
 	mutex_lock(&kernfs_mutex);
 
 	list_for_each_entry(info, &kernfs_root(kn)->supers, node) {
 		struct kernfs_node *parent;
 		struct inode *inode;
+		struct qstr name;
 
 		/*
 		 * We want fsnotify_modify() on @kn but as the
@@ -899,6 +896,7 @@
 		if (!inode)
 			continue;
 
+		name = (struct qstr)QSTR_INIT(kn->name, strlen(kn->name));
 		parent = kernfs_get_parent(kn);
 		if (parent) {
 			struct inode *p_inode;
@@ -906,7 +904,7 @@
 			p_inode = ilookup(info->sb, parent->id.ino);
 			if (p_inode) {
 				fsnotify(p_inode, FS_MODIFY | FS_EVENT_ON_CHILD,
-					 inode, FSNOTIFY_EVENT_INODE, kn->name, 0);
+					 inode, FSNOTIFY_EVENT_INODE, &name, 0);
 				iput(p_inode);
 			}
 
@@ -914,7 +912,7 @@
 		}
 
 		fsnotify(inode, FS_MODIFY, inode, FSNOTIFY_EVENT_INODE,
-			 kn->name, 0);
+			 &name, 0);
 		iput(inode);
 	}
 
@@ -934,10 +932,21 @@
 {
 	static DECLARE_WORK(kernfs_notify_work, kernfs_notify_workfn);
 	unsigned long flags;
+	struct kernfs_open_node *on;
 
 	if (WARN_ON(kernfs_type(kn) != KERNFS_FILE))
 		return;
 
+	/* kick poll immediately */
+	spin_lock_irqsave(&kernfs_open_node_lock, flags);
+	on = kn->attr.open;
+	if (on) {
+		atomic_inc(&on->event);
+		wake_up_interruptible(&on->poll);
+	}
+	spin_unlock_irqrestore(&kernfs_open_node_lock, flags);
+
+	/* schedule work to kick fsnotify */
 	spin_lock_irqsave(&kernfs_notify_lock, flags);
 	if (!kn->attr.notify_next) {
 		kernfs_get(kn);