Re: [PATCH v3 3/3] mm: use vma_start_write_killable() in process_vma_walk_lock()

[Suren Baghdasaryan <surenb@google.com>]

On Thu, Feb 26, 2026 at 10:10 AM Claudio Imbrenda
<imbrenda@linux.ibm.com> wrote:
>
> On Wed, 25 Feb 2026 23:06:09 -0800
> Suren Baghdasaryan <surenb@google.com> wrote:
>
> > Replace vma_start_write() with vma_start_write_killable() when
> > process_vma_walk_lock() is used with PGWALK_WRLOCK option.
> > Adjust its direct and indirect users to check for a possible error
> > and handle it. Ensure users handle EINTR correctly and do not ignore
> > it.
> >
> > Signed-off-by: Suren Baghdasaryan <surenb@google.com>
> > ---
> >  arch/s390/kvm/kvm-s390.c |  2 +-
> >  fs/proc/task_mmu.c       |  5 ++++-
> >  mm/mempolicy.c           | 14 +++++++++++---
> >  mm/pagewalk.c            | 20 ++++++++++++++------
> >  mm/vma.c                 | 22 ++++++++++++++--------
> >  mm/vma.h                 |  6 ++++++
> >  6 files changed, 50 insertions(+), 19 deletions(-)
> >
> > diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
> > index 7a175d86cef0..337e4f7db63a 100644
> > --- a/arch/s390/kvm/kvm-s390.c
> > +++ b/arch/s390/kvm/kvm-s390.c
> > @@ -2948,7 +2948,7 @@ int kvm_arch_vm_ioctl(struct file *filp, unsigned int ioctl, unsigned long arg)
> >               }
> >               /* must be called without kvm->lock */
> >               r = kvm_s390_handle_pv(kvm, &args);
> > -             if (copy_to_user(argp, &args, sizeof(args))) {
> > +             if (r != -EINTR && copy_to_user(argp, &args, sizeof(args))) {
> >                       r = -EFAULT;
> >                       break;
> >               }
>
> can you very briefly explain how we can end up with -EINTR here?
>
> do I understand correctly that -EINTR is possible here only if the
> process is being killed?

Correct, it would happen if the process has a pending fatal signal
(like SIGKILL) in its signal queue.

>
> [...]