btrfs: export wait_extent_bit

This is used by the subpage code in addition to lock_extent_bits, so
export it so we can move it out of extent_io.c
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/extent-io-tree.h

@@ -253,6 +253,7 @@ int extent_invalidate_folio(struct extent_io_tree *tree,
 bool btrfs_find_delalloc_range(struct extent_io_tree *tree, u64 *start,
 			       u64 *end, u64 max_bytes,
 			       struct extent_state **cached_state);
+void wait_extent_bit(struct extent_io_tree *tree, u64 start, u64 end, u32 bits);
 
 /* This should be reworked in the future and put elsewhere. */
 void btrfs_free_io_failure_record(struct btrfs_inode *inode, u64 start,

fs/btrfs/extent_io.c

@@ -753,8 +753,7 @@ static void wait_on_state(struct extent_io_tree *tree,
  * The range [start, end] is inclusive.
  * The tree lock is taken by this function
  */
-static void wait_extent_bit(struct extent_io_tree *tree, u64 start, u64 end,
-			    u32 bits)
+void wait_extent_bit(struct extent_io_tree *tree, u64 start, u64 end, u32 bits)
 {
 	struct extent_state *state;
 	struct rb_node *node;