btrfs: backref: rename and move should_ignore_root()

This function is mostly single purpose to relocation backref cache, but
since we're moving the main part of backref cache to backref.c, we need
to export such function.

And to avoid confusion, rename the function to
btrfs_should_ignore_reloc_root() make the name a little more clear.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/ctree.h

@@ -3383,6 +3383,7 @@ int btrfs_reloc_post_snapshot(struct btrfs_trans_handle *trans,
 int btrfs_should_cancel_balance(struct btrfs_fs_info *fs_info);
 struct btrfs_root *find_reloc_root(struct btrfs_fs_info *fs_info,
 				   u64 bytenr);
+int btrfs_should_ignore_reloc_root(struct btrfs_root *root);
 
 /* scrub.c */
 int btrfs_scrub_dev(struct btrfs_fs_info *fs_info, u64 devid, u64 start,

fs/btrfs/relocation.c

@@ -305,7 +305,8 @@ static bool reloc_root_is_dead(struct btrfs_root *root)
  *
  * Reloc tree after swap is considered dead, thus not considered as valid.
  * This is enough for most callers, as they don't distinguish dead reloc root
- * from no reloc root.  But should_ignore_root() below is a special case.
+ * from no reloc root.  But btrfs_should_ignore_reloc_root() below is a
+ * special case.
  */
 static bool have_reloc_root(struct btrfs_root *root)
 {
@@ -316,7 +317,7 @@ static bool have_reloc_root(struct btrfs_root *root)
 	return true;
 }
 
-static int should_ignore_root(struct btrfs_root *root)
+int btrfs_should_ignore_reloc_root(struct btrfs_root *root)
 {
 	struct btrfs_root *reloc_root;
 
@@ -342,6 +343,7 @@ static int should_ignore_root(struct btrfs_root *root)
 	 */
 	return 1;
 }
+
 /*
  * find reloc tree by address of tree root
  */
@@ -485,7 +487,7 @@ static int handle_indirect_tree_backref(struct btrfs_backref_cache *cache,
 	if (btrfs_root_level(&root->root_item) == cur->level) {
 		/* Tree root */
 		ASSERT(btrfs_root_bytenr(&root->root_item) == cur->bytenr);
-		if (should_ignore_root(root)) {
+		if (btrfs_should_ignore_reloc_root(root)) {
 			btrfs_put_root(root);
 			list_add(&cur->list, &cache->useless_node);
 		} else {
@@ -526,7 +528,7 @@ static int handle_indirect_tree_backref(struct btrfs_backref_cache *cache,
 		if (!path->nodes[level]) {
 			ASSERT(btrfs_root_bytenr(&root->root_item) ==
 			       lower->bytenr);
-			if (should_ignore_root(root)) {
+			if (btrfs_should_ignore_reloc_root(root)) {
 				btrfs_put_root(root);
 				list_add(&lower->list, &cache->useless_node);
 			} else {