A memory leak problem for aufs/squashfs/tmpfs

I find a possible memory leak problem for aufs or tmpfs.

I use Linux kernel 2.6.16. It's old but I have to use it. To save memory and disk space, I use aufs+squashfs. Lots of files are stored in squashfs, which is mounted as /ro. The changed files are stored in tmpfs, which is mounted as /rw.

There is a strange thing after the system runs for two weeks. Because some files are modified, there are several files in /rw. The total file size in /rw is about 10MB. But from df, I find the used size of /rw is about 200MB. (Tmpfs files are all stored in Linux Page cache, so the increased cache size is also about 200MB.) I don't know where is the remaining 190MB memory space.

Are there any memory leaks for aufs, squashfs or tmpfs? Because of the old kernel, I开发者_运维问答 use latest code of aufs1, not aufs2.x. Also because of the old kernel, I use stable version of squashfs 3.4, not 4.x. There versions of code are not maintained. Does anyone know there are some memory leak bugs for them? Of does tempfs code have problems in kernel 2.6.16?

You can try

sync && echo 3 >/proc/sys/vm/drop_caches

and see if you still have the same figures in df