btrfs: make btrfs_assert_tree_locked static inline

The function btrfs_assert_tree_locked is used outside of the locking
code so it is exported, however we can make it static inine as it's
fairly trivial.

This is the only locking assertion used in release builds, inlining
improves the text size by 174 bytes and reduces stack consumption in the
callers.
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/locking.c

@@ -67,11 +67,6 @@ static inline void btrfs_assert_tree_write_locks_put(struct extent_buffer *eb)
 	eb->write_locks--;
 }
 
-void btrfs_assert_tree_locked(struct extent_buffer *eb)
-{
-	BUG_ON(!eb->write_locks);
-}
-
 #else
 static void btrfs_assert_spinning_writers_get(struct extent_buffer *eb) { }
 static void btrfs_assert_spinning_writers_put(struct extent_buffer *eb) { }
@@ -81,7 +76,6 @@ static void btrfs_assert_spinning_readers_get(struct extent_buffer *eb) { }
 static void btrfs_assert_tree_read_locked(struct extent_buffer *eb) { }
 static void btrfs_assert_tree_read_locks_get(struct extent_buffer *eb) { }
 static void btrfs_assert_tree_read_locks_put(struct extent_buffer *eb) { }
-void btrfs_assert_tree_locked(struct extent_buffer *eb) { }
 static void btrfs_assert_tree_write_locks_get(struct extent_buffer *eb) { }
 static void btrfs_assert_tree_write_locks_put(struct extent_buffer *eb) { }
 #endif

fs/btrfs/locking.h

@@ -6,6 +6,8 @@
 #ifndef BTRFS_LOCKING_H
 #define BTRFS_LOCKING_H
 
+#include "extent_io.h"
+
 #define BTRFS_WRITE_LOCK 1
 #define BTRFS_READ_LOCK 2
 #define BTRFS_WRITE_LOCK_BLOCKING 3
@@ -19,11 +21,17 @@ void btrfs_tree_read_unlock(struct extent_buffer *eb);
 void btrfs_tree_read_unlock_blocking(struct extent_buffer *eb);
 void btrfs_set_lock_blocking_read(struct extent_buffer *eb);
 void btrfs_set_lock_blocking_write(struct extent_buffer *eb);
-void btrfs_assert_tree_locked(struct extent_buffer *eb);
 int btrfs_try_tree_read_lock(struct extent_buffer *eb);
 int btrfs_try_tree_write_lock(struct extent_buffer *eb);
 int btrfs_tree_read_lock_atomic(struct extent_buffer *eb);
 
+#ifdef CONFIG_BTRFS_DEBUG
+static inline void btrfs_assert_tree_locked(struct extent_buffer *eb) {
+	BUG_ON(!eb->write_locks);
+}
+#else
+static inline void btrfs_assert_tree_locked(struct extent_buffer *eb) { }
+#endif
 
 static inline void btrfs_tree_unlock_rw(struct extent_buffer *eb, int rw)
 {