On Tue, Jan 08, 2019 at 09:02:03PM -0500, Andrea Arcangeli wrote:
> hugetlb needs the same fix as faultin_nopage (which was applied in
> 96312e61282ae3f6537a562625706498cbc75594) or KVM hangs because it
> thinks the mmap_sem was already released by hugetlb_fault() if it
> returned VM_FAULT_RETRY, but it wasn't in the FOLL_NOWAIT case.
>
> Fixes: ce53053ce378 ("kvm: switch get_user_page_nowait() to get_user_pages_unlocked()")
> Signed-off-by: Andrea Arcangeli <aarcange@xxxxxxxxxx>
> Tested-by: "Dr. David Alan Gilbert" <dgilbert@xxxxxxxxxx>
> Reported-by: "Dr. David Alan Gilbert" <dgilbert@xxxxxxxxxx>
FWIW:
Reviewed-by: Peter Xu <peterx@xxxxxxxxxx>
> ---
> mm/hugetlb.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index e37efd5d8318..b3622d7888c8 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -4301,7 +4301,8 @@ long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
> break;
> }
> if (ret & VM_FAULT_RETRY) {
> - if (nonblocking)
> + if (nonblocking &&
> + !(fault_flags & FAULT_FLAG_RETRY_NOWAIT))
> *nonblocking = 0;
> *nr_pages = 0;
> /*
Regards,
--
Peter Xu
