252 /* Sync real dirty inodes in upper filesystem (if it exists) */
287  * Get the filesystem statistics.  As writes always target the upper layer
288  * filesystem pass the statfs to the upper filesystem (if it exists)
568 	/* Workdir is useless in non-upper mount */  in ovl_parse_opt()
570 		pr_info("overlayfs: option \"workdir=%s\" is useless in a non-upper mount, ignore\n",  in ovl_parse_opt()
582 	 * difference, since config->redirect_dir is only used for upper.  in ovl_parse_opt()
665 		 * allowed as upper are limited to "normal" ones, where checking  in ovl_workdir_create()
1036 	/* Upper fs should not be r/o */  in ovl_get_upper()
1038 		pr_err("overlayfs: upper fs is r/o, try multi-lower layers mount\n");  in ovl_get_upper()
1097 	 * Upper should support d_type, else whiteouts are visible.  Given  in ovl_make_workdir()
1098 	 * workdir and upper are on same fs, we can do iterate_dir() on  in ovl_make_workdir()
1111 		pr_warn("overlayfs: upper fs needs to support d_type.\n");  in ovl_make_workdir()
1113 	/* Check if upper/work fs supports O_TMPFILE */  in ovl_make_workdir()
1119 		pr_warn("overlayfs: upper fs does not support tmpfile.\n");  in ovl_make_workdir()
1122 	 * Check if upper/work fs supports trusted.overlay.* xattr  in ovl_make_workdir()
1129 …pr_warn("overlayfs: upper fs does not support xattr, falling back to index=off and metacopy=off.\n…  in ovl_make_workdir()
1135 	/* Check if upper/work fs supports file handles */  in ovl_make_workdir()
1139 		pr_warn("overlayfs: upper fs does not support file handles, falling back to index=off.\n");  in ovl_make_workdir()
1142 	/* Check if upper fs has 32bit inode numbers */  in ovl_make_workdir()
1209 	/* Verify lower root is upper root origin */  in ovl_get_indexdir()
1213 		pr_err("overlayfs: failed to verify upper root origin\n");  in ovl_get_indexdir()
1225 		 * Verify upper root is exclusively associated with index dir.  in ovl_get_indexdir()
1226 		 * Older kernels stored upper fh in "trusted.overlay.origin"  in ovl_get_indexdir()
1228 		 * upper dir file handle. In any case, verify or set xattr  in ovl_get_indexdir()
1229 		 * "trusted.overlay.upper" to indicate that index may have  in ovl_get_indexdir()
1240 			pr_err("overlayfs: failed to verify index dir 'upper' xattr\n");  in ovl_get_indexdir()
1281 	/* fsid 0 is reserved for upper fs even with non upper overlay */  in ovl_get_fsid()
1387 		 * upper fs even with non upper overlay.  in ovl_get_lower_layers()
1394 		pr_info("overlayfs: \"xino\" feature enabled using %d upper inode bits.\n",  in ovl_get_lower_layers()
1429 …pr_warn("overlayfs: NFS export requires \"redirect_dir=nofollow\" on non-upper mount, falling back…  in ovl_get_lowerstack()
1491  * - upper/work dir of any overlayfs instance
1627 	/* If the upper fs is nonexistent, we mark overlayfs r/o too */  in ovl_fill_super()