On Tue, 15 Aug 2023, David Hildenbrand wrote:
> On 15.08.23 08:34, Hugh Dickins wrote:
> > On Mon, 14 Aug 2023, Jann Horn wrote:
> >>
> >> /* step 4: remove page table */
> >> + if (strcmp(current->comm, "DELAYME") == 0) {
> >> + pr_warn("%s: BEGIN DELAY INJECTION\n", __func__);
> >> + mdelay(5000);
> >> + pr_warn("%s: END DELAY INJECTION\n", __func__);
> >> + }
> >>
> >> /* Huge page lock is still held, so page table must remain empty
> >> */
> >> pml = pmd_lock(mm, pmd);
> >>
> >>
> >> And then run the attached reproducer against mm/mm-everything. You
> >> should get this in dmesg:
> >>
> >> [ 206.578096] BUG: Bad rss-counter state mm:000000000942ebea
> >> type:MM_ANONPAGES val:1
> >
> > Thanks a lot, Jann. I haven't thought about it at all yet; and just
> > tried to reproduce, but haven't yet got the "BUG: Bad rss-counter":
> > just see "Invalid argument" on the UFFDIO_COPY ioctl.
> > Will investigate tomorrow.
>
> Maybe you're missing a fixup:
>
> https://lkml.kernel.org/r/20230810192128.1855570-1-axelrasmussen@xxxxxxxxxx
>
> When the src address is not page aligned, UFFDIO_COPY in mm-unstable would
> erroneously fail.
You got it, many thanks David: I had assumed that my next-20230808 tree
would be up-to-date enough, but it wasn't. Reproduced now.
Hugh
