Hi, Andrew,
On Wed, Mar 24, 2021 at 04:20:27PM -0700, Andrew Morton wrote:
> On Mon, 22 Mar 2021 13:48:35 -0700 Axel Rasmussen <axelrasmussen@xxxxxxxxxx> wrote:
>
> > This fix is analogous to Peter Xu's fix for hugetlb [0]. If we don't
> > put_page() after getting the page out of the page cache, we leak the
> > reference.
> >
> > The fix can be verified by checking /proc/meminfo and running the
> > userfaultfd selftest in shmem mode. Without the fix, we see MemFree /
> > MemAvailable steadily decreasing with each run of the test. With the
> > fix, memory is correctly freed after the test program exits.
> >
> > Fixes: 00da60b9d0a0 ("userfaultfd: support minor fault handling for shmem")
>
> Confused. The affected code:
>
> > --- a/mm/shmem.c
> > +++ b/mm/shmem.c
> > @@ -1831,6 +1831,7 @@ static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
> >
> > if (page && vma && userfaultfd_minor(vma)) {
> > unlock_page(page);
> > + put_page(page);
> > *fault_type = handle_userfault(vmf, VM_UFFD_MINOR);
> > return 0;
> > }
>
> Is added by Peter's "page && vma && userfaultfd_minor". I assume that
> "Fixes:" is incorrect?
>
It seems to me the commit is correct as pointed to in "Fixes", but I do have a
different commit ID here:
commit 63c826b1372c4930f89b8a55092699fa7f0d6f4e
Author: Axel Rasmussen <axelrasmussen@xxxxxxxxxx>
Date: Thu Mar 18 10:20:43 2021 -0400
userfaultfd: support minor fault handling for shmem
Axel, did you fetched the commit ID from your local tree, perhaps? Since I
should have fetched from hnaz/linux-mm and I can see Andrew's sign-off too.
Thanks,
--
Peter Xu
