On Sun, 26 Apr 2026 11:08:22 +0000 fujunjie <[email protected]> wrote:
> process_madvise() validates the advice while walking the imported iovec. Seems inefficient to be checking `behavior' repeatedly. I wonder if your change will permit us to remove that madvise_behavior_valid() check from is_valid_madvise(). > If the iovec has zero total length, vector_madvise() never enters the > loop and returns 0 without checking whether the advice value is valid. > > For a local mm, such as process_madvise(PIDFD_SELF, ...), the remote-only > process_madvise_remote_valid() check is skipped. As a result, an invalid > advice can be reported as success when the vector has zero total length. > This differs from madvise(), which rejects an invalid advice before > returning success for a zero-length range. > > Reject invalid advice before walking the vector. Valid zero-length > requests remain no-ops and continue to return 0. > > Add a selftest that covers invalid advice with a zero-length iovec and an > empty vector, while also checking that a valid zero-length request still > succeeds. lgtm, thanks. Slightly non-backward-compatible but I think we can live with that. My process_madvise manpage doesn't even anticipate bogus `advice' parameters. And grr, the manpage calls it `advice' but the kernel calls it `behavior'.
