btrfs: rename and export __btrfs_cow_block()

Rename and export __btrfs_cow_block() as btrfs_force_cow_block(). This is
to allow to move defrag specific code out of ctree.c and into defrag.c in
one of the next patches.
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/ctree.c

@@ -510,7 +510,7 @@ static noinline int update_ref_for_cow(struct btrfs_trans_handle *trans,
  * bytes the allocator should try to find free next to the block it returns.
  * This is just a hint and may be ignored by the allocator.
  */
-static noinline int __btrfs_cow_block(struct btrfs_trans_handle *trans,
+int btrfs_force_cow_block(struct btrfs_trans_handle *trans,
 			  struct btrfs_root *root,
 			  struct extent_buffer *buf,
 			  struct extent_buffer *parent, int parent_slot,
@@ -674,7 +674,7 @@ static inline int should_cow_block(struct btrfs_trans_handle *trans,
 }
 
 /*
- * cows a single block, see __btrfs_cow_block for the real work.
+ * COWs a single block, see btrfs_force_cow_block() for the real work.
  * This version of it has extra checks so that a block isn't COWed more than
  * once per transaction, as long as it hasn't been written yet
  */
@@ -727,8 +727,8 @@ int btrfs_cow_block(struct btrfs_trans_handle *trans,
 	 * Also We don't care about the error, as it's handled internally.
 	 */
 	btrfs_qgroup_trace_subtree_after_cow(trans, root, buf);
-	ret = __btrfs_cow_block(trans, root, buf, parent,
-				 parent_slot, cow_ret, search_start, 0, nest);
+	ret = btrfs_force_cow_block(trans, root, buf, parent, parent_slot,
+				    cow_ret, search_start, 0, nest);
 
 	trace_btrfs_cow_block(root, buf, *cow_ret);
 
@@ -879,7 +879,7 @@ int btrfs_realloc_node(struct btrfs_trans_handle *trans,
 			search_start = last_block;
 
 		btrfs_tree_lock(cur);
-		err = __btrfs_cow_block(trans, root, cur, parent, i,
+		err = btrfs_force_cow_block(trans, root, cur, parent, i,
 					    &cur, search_start,
 					    min(16 * blocksize,
 						(end_slot - i) * blocksize),

fs/btrfs/ctree.h

@@ -487,6 +487,13 @@ int btrfs_cow_block(struct btrfs_trans_handle *trans,
 		    struct extent_buffer *parent, int parent_slot,
 		    struct extent_buffer **cow_ret,
 		    enum btrfs_lock_nesting nest);
+int btrfs_force_cow_block(struct btrfs_trans_handle *trans,
+			  struct btrfs_root *root,
+			  struct extent_buffer *buf,
+			  struct extent_buffer *parent, int parent_slot,
+			  struct extent_buffer **cow_ret,
+			  u64 search_start, u64 empty_size,
+			  enum btrfs_lock_nesting nest);
 int btrfs_copy_root(struct btrfs_trans_handle *trans,
 		      struct btrfs_root *root,
 		      struct extent_buffer *buf,