btrfs: zoned: factor out prepare_allocation_zoned()

Factor out prepare_allocation_zoned() for further extension. While at
it, optimize the if-branch a bit.
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/extent-tree.c

@@ -4298,29 +4298,35 @@ static int prepare_allocation_clustered(struct btrfs_fs_info *fs_info,
 	return 0;
 }
 
-static int prepare_allocation(struct btrfs_fs_info *fs_info,
-			      struct find_free_extent_ctl *ffe_ctl,
-			      struct btrfs_space_info *space_info,
-			      struct btrfs_key *ins)
+static int prepare_allocation_zoned(struct btrfs_fs_info *fs_info,
+				    struct find_free_extent_ctl *ffe_ctl)
 {
-	switch (ffe_ctl->policy) {
-	case BTRFS_EXTENT_ALLOC_CLUSTERED:
-		return prepare_allocation_clustered(fs_info, ffe_ctl,
-						    space_info, ins);
-	case BTRFS_EXTENT_ALLOC_ZONED:
 	if (ffe_ctl->for_treelog) {
 		spin_lock(&fs_info->treelog_bg_lock);
 		if (fs_info->treelog_bg)
 			ffe_ctl->hint_byte = fs_info->treelog_bg;
 		spin_unlock(&fs_info->treelog_bg_lock);
-		}
-		if (ffe_ctl->for_data_reloc) {
+	} else if (ffe_ctl->for_data_reloc) {
 		spin_lock(&fs_info->relocation_bg_lock);
 		if (fs_info->data_reloc_bg)
 			ffe_ctl->hint_byte = fs_info->data_reloc_bg;
 		spin_unlock(&fs_info->relocation_bg_lock);
 	}
+
 	return 0;
+}
+
+static int prepare_allocation(struct btrfs_fs_info *fs_info,
+			      struct find_free_extent_ctl *ffe_ctl,
+			      struct btrfs_space_info *space_info,
+			      struct btrfs_key *ins)
+{
+	switch (ffe_ctl->policy) {
+	case BTRFS_EXTENT_ALLOC_CLUSTERED:
+		return prepare_allocation_clustered(fs_info, ffe_ctl,
+						    space_info, ins);
+	case BTRFS_EXTENT_ALLOC_ZONED:
+		return prepare_allocation_zoned(fs_info, ffe_ctl);
 	default:
 		BUG();
 	}