Update Linux to v5.4.2

Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/include/linux/sunrpc/cache.h b/include/linux/sunrpc/cache.h
index 40d2822..f860372 100644
--- a/include/linux/sunrpc/cache.h
+++ b/include/linux/sunrpc/cache.h
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
 /*
  * include/linux/sunrpc/cache.h
  *
@@ -5,9 +6,6 @@
  * used by sunrpc clients and servers.
  *
  * Copyright (C) 2002 Neil Brown <neilb@cse.unsw.edu.au>
- *
- * Released under terms in GPL version 2.  See COPYING.
- *
  */
 
 #ifndef _LINUX_SUNRPC_CACHE_H_
@@ -67,7 +65,7 @@
 	struct module *		owner;
 	int			hash_size;
 	struct hlist_head *	hash_table;
-	rwlock_t		hash_lock;
+	spinlock_t		hash_lock;
 
 	char			*name;
 	void			(*cache_put)(struct kref *);
@@ -89,6 +87,7 @@
 					      int has_died);
 
 	struct cache_head *	(*alloc)(void);
+	void			(*flush)(void);
 	int			(*match)(struct cache_head *orig, struct cache_head *new);
 	void			(*init)(struct cache_head *orig, struct cache_head *new);
 	void			(*update)(struct cache_head *orig, struct cache_head *new);
@@ -109,9 +108,9 @@
 	/* fields for communication over channel */
 	struct list_head	queue;
 
-	atomic_t		readers;		/* how many time is /chennel open */
-	time_t			last_close;		/* if no readers, when did last close */
-	time_t			last_warn;		/* when we last warned about no readers */
+	atomic_t		writers;		/* how many time is /channel open */
+	time_t			last_close;		/* if no writers, when did last close */
+	time_t			last_warn;		/* when we last warned about no writers */
 
 	union {
 		struct proc_dir_entry	*procfs;
@@ -168,8 +167,8 @@
 extern const struct file_operations cache_flush_operations_pipefs;
 
 extern struct cache_head *
-sunrpc_cache_lookup(struct cache_detail *detail,
-		    struct cache_head *key, int hash);
+sunrpc_cache_lookup_rcu(struct cache_detail *detail,
+			struct cache_head *key, int hash);
 extern struct cache_head *
 sunrpc_cache_update(struct cache_detail *detail,
 		    struct cache_head *new, struct cache_head *old, int hash);
@@ -186,6 +185,12 @@
 	return h;
 }
 
+static inline struct cache_head  *cache_get_rcu(struct cache_head *h)
+{
+	if (kref_get_unless_zero(&h->ref))
+		return h;
+	return NULL;
+}
 
 static inline void cache_put(struct cache_head *h, struct cache_detail *cd)
 {
@@ -224,9 +229,9 @@
 extern void sunrpc_cache_unhash(struct cache_detail *, struct cache_head *);
 
 /* Must store cache_detail in seq_file->private if using next three functions */
-extern void *cache_seq_start(struct seq_file *file, loff_t *pos);
-extern void *cache_seq_next(struct seq_file *file, void *p, loff_t *pos);
-extern void cache_seq_stop(struct seq_file *file, void *p);
+extern void *cache_seq_start_rcu(struct seq_file *file, loff_t *pos);
+extern void *cache_seq_next_rcu(struct seq_file *file, void *p, loff_t *pos);
+extern void cache_seq_stop_rcu(struct seq_file *file, void *p);
 
 extern void qword_add(char **bpp, int *lp, char *str);
 extern void qword_addhex(char **bpp, int *lp, char *buf, int blen);