erofs: clean up z_erofs_collector_begin()

Rearrange the code and get rid of all gotos.

Reviewed-by: Yue Hu <huyue2@coolpad.com>
Acked-by: Chao Yu <chao@kernel.org>
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Link: https://lore.kernel.org/r/20220715154203.48093-3-hsiangkao@linux.alibaba.com

fs/erofs/zdata.c

@@ -521,7 +521,7 @@ err_out:
 static int z_erofs_collector_begin(struct z_erofs_decompress_frontend *fe)
 {
 	struct erofs_map_blocks *map = &fe->map;
-	struct erofs_workgroup *grp;
+	struct erofs_workgroup *grp = NULL;
 	int ret;
 
 	DBG_BUGON(fe->pcl);
@@ -530,33 +530,31 @@ static int z_erofs_collector_begin(struct z_erofs_decompress_frontend *fe)
 	DBG_BUGON(fe->owned_head == Z_EROFS_PCLUSTER_NIL);
 	DBG_BUGON(fe->owned_head == Z_EROFS_PCLUSTER_TAIL_CLOSED);
 
-	if (map->m_flags & EROFS_MAP_META) {
-		if ((map->m_pa & ~PAGE_MASK) + map->m_plen > PAGE_SIZE) {
-			DBG_BUGON(1);
-			return -EFSCORRUPTED;
-		}
-		goto tailpacking;
+	if (!(map->m_flags & EROFS_MAP_META)) {
+		grp = erofs_find_workgroup(fe->inode->i_sb,
+					   map->m_pa >> PAGE_SHIFT);
+	} else if ((map->m_pa & ~PAGE_MASK) + map->m_plen > PAGE_SIZE) {
+		DBG_BUGON(1);
+		return -EFSCORRUPTED;
 	}
 
-	grp = erofs_find_workgroup(fe->inode->i_sb, map->m_pa >> PAGE_SHIFT);
 	if (grp) {
 		fe->pcl = container_of(grp, struct z_erofs_pcluster, obj);
+		ret = -EEXIST;
 	} else {
-tailpacking:
 		ret = z_erofs_register_pcluster(fe);
-		if (!ret)
-			goto out;
-		if (ret != -EEXIST)
-			return ret;
 	}
 
-	ret = z_erofs_lookup_pcluster(fe);
-	if (ret) {
-		erofs_workgroup_put(&fe->pcl->obj);
+	if (ret == -EEXIST) {
+		ret = z_erofs_lookup_pcluster(fe);
+		if (ret) {
+			erofs_workgroup_put(&fe->pcl->obj);
+			return ret;
+		}
+	} else if (ret) {
 		return ret;
 	}
 
-out:
 	z_erofs_pagevec_ctor_init(&fe->vector, Z_EROFS_NR_INLINE_PAGEVECS,
 				  fe->pcl->pagevec, fe->pcl->vcnt);
 	/* since file-backed online pages are traversed in reverse order */