Gerhard Jaeger writes:

The facts:
- mmap the last page @ 0xFFFFF000, len 4K
- result: mmap says EOVERFLOW...
- the function that failed was do_mmap_pgoff()

Here's the pice of code

/* offset overflow? */
if ((pgoff + (len >> PAGE_SHIFT)) < pgoff)
    return -EOVERFLOW;

It's quite clear why it fails in my case:
pgoff + (len >> PAGE_SHIFT) will be 0

No, pgoff will be 0xfffff, len will be 1, the sum is 0x100000.  You
need to look elsewhere for the problem.

Paul.