Linux kernel: log all file access

Question

On a very constrained embedded Linux system, I wish to log all files that are opened/mapped/whatever for read and or write. In other words, all files that are accessed at least once. What would be the best approach? Because of "some" constraints, I would prefer NOT to modify/hack the file system, init scripts and the user-space level... I think that I would prefer to do things in the kernel. Even an insertion of printk in the right functions would be acceptable. If that matters, I'm using an ext3 filesystem.

Answer 1

Answering my own question. Patching the kernel file system driver is a working solution:

char *buf = (char*)__get_free_page(GFP_USER);
char *name = dentry_path_raw(file->f_dentry, buf, PAGE_SIZE);
printk("FILE OPEN read: %d write: %d %s\n", file->f_mode & FMODE_READ, file->f_mode & FMODE_WRITE, name);
free_page((unsigned long)buf);