ocfs2: Add functions for extents refcounted.

Add function ocfs2_mark_extent_refcounted which can mark
an extent refcounted.
Signed-off-by: Tao Ma <tao.ma@oracle.com>

fs/ocfs2/alloc.c

@@ -5169,7 +5169,7 @@ int ocfs2_split_extent(handle_t *handle,
  *
  * The caller is responsible for passing down meta_ac if we'll need it.
  */
-static int ocfs2_change_extent_flag(handle_t *handle,
+int ocfs2_change_extent_flag(handle_t *handle,
 			     struct ocfs2_extent_tree *et,
 			     u32 cpos, u32 len, u32 phys,
 			     struct ocfs2_alloc_context *meta_ac,

fs/ocfs2/alloc.h

@@ -128,6 +128,12 @@ int ocfs2_mark_extent_written(struct inode *inode,
 			      handle_t *handle, u32 cpos, u32 len, u32 phys,
 			      struct ocfs2_alloc_context *meta_ac,
 			      struct ocfs2_cached_dealloc_ctxt *dealloc);
+int ocfs2_change_extent_flag(handle_t *handle,
+			     struct ocfs2_extent_tree *et,
+			     u32 cpos, u32 len, u32 phys,
+			     struct ocfs2_alloc_context *meta_ac,
+			     struct ocfs2_cached_dealloc_ctxt *dealloc,
+			     int new_flags, int clear_flags);
 int ocfs2_remove_extent(handle_t *handle, struct ocfs2_extent_tree *et,
 			u32 cpos, u32 len,
 			struct ocfs2_alloc_context *meta_ac,

fs/ocfs2/ocfs2.h

@@ -516,6 +516,13 @@ static inline void ocfs2_add_links_count(struct ocfs2_dinode *di, int n)
 	ocfs2_set_links_count(di, links);
 }
 
+static inline int ocfs2_refcount_tree(struct ocfs2_super *osb)
+{
+	if (osb->s_feature_incompat & OCFS2_FEATURE_INCOMPAT_REFCOUNT_TREE)
+		return 1;
+	return 0;
+}
+
 /* set / clear functions because cluster events can make these happen
  * in parallel so we want the transitions to be atomic. this also
  * means that any future flags osb_flags must be protected by spinlock

fs/ocfs2/refcounttree.c

@@ -2153,3 +2153,42 @@ int ocfs2_decrease_refcount(struct inode *inode,
 	brelse(ref_root_bh);
 	return ret;
 }
+
+/*
+ * Mark the already-existing extent at cpos as refcounted for len clusters.
+ * This adds the refcount extent flag.
+ *
+ * If the existing extent is larger than the request, initiate a
+ * split. An attempt will be made at merging with adjacent extents.
+ *
+ * The caller is responsible for passing down meta_ac if we'll need it.
+ */
+static int ocfs2_mark_extent_refcounted(struct inode *inode,
+				struct ocfs2_extent_tree *et,
+				handle_t *handle, u32 cpos,
+				u32 len, u32 phys,
+				struct ocfs2_alloc_context *meta_ac,
+				struct ocfs2_cached_dealloc_ctxt *dealloc)
+{
+	int ret;
+
+	mlog(0, "Inode %lu refcount tree cpos %u, len %u, phys cluster %u\n",
+	     inode->i_ino, cpos, len, phys);
+
+	if (!ocfs2_refcount_tree(OCFS2_SB(inode->i_sb))) {
+		ocfs2_error(inode->i_sb, "Inode %lu want to use refcount "
+			    "tree, but the feature bit is not set in the "
+			    "super block.", inode->i_ino);
+		ret = -EROFS;
+		goto out;
+	}
+
+	ret = ocfs2_change_extent_flag(handle, et, cpos,
+				       len, phys, meta_ac, dealloc,
+				       OCFS2_EXT_REFCOUNTED, 0);
+	if (ret)
+		mlog_errno(ret);
+
+out:
+	return ret;
+}