Hi, now i'm interested in mount lenght of max mount option. I anaylsis ksys_mount() function in /fs/namespace.c. and find out the length of max mount option is a page size (4096 bytes). I know that almost mount option short and page size is enough to contain almost mount options. but because of options for unionfs(overlay, aufs), lenght of mount option could be exceed it and cut. I suffer this problem with aufs. aufs's branch option is cut and fail to aufs mount. I know that aufs is not offical fs in linux, but overlay fs now support multi layer mount option and could be suffer the same problem. I think the best is dynamic allocate mount option's kernel memory. but I'm only have shallow knowlege of kernel, I can't guess it. And I think If the length of mount option cannot exceed a page size, kernel must leave warning messsage about lenght and return err. copy_mount_options() function seems to done this.
