btrfs: add forward declarations and headers, part 1

Do a cleanup in the short headers:

- add forward declarations for types referenced by pointers
- add includes when types need them

This fixes potential compilation problems if the headers are reordered
or the missing includes are not provided indirectly.

Signed-off-by: David Sterba <dsterba@suse.com>

1 files changed, 6 insertions, 0 deletions

diff --git a/fs/btrfs/rcu-string.h b/fs/btrfs/rcu-string.h
index 5c2b66d155ef..1c2d7cb1fe6f 100644
--- a/fs/btrfs/rcu-string.h
+++ b/fs/btrfs/rcu-string.h
@@ -6,6 +6,12 @@
 #ifndef BTRFS_RCU_STRING_H
 #define BTRFS_RCU_STRING_H
 
+#include <linux/types.h>
+#include <linux/string.h>
+#include <linux/slab.h>
+#include <linux/rcupdate.h>
+#include <linux/printk.h>
+
 struct rcu_string {
 	struct rcu_head rcu;
 	char str[];