linux-kernel - Re: [PATCH v4 26/26] mm/gup: Remove task

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Date:   Thu, 2 Jul 2020 20:52:55 -0400
From:   Peter Xu <peterx@...hat.com>
To:     John Hubbard <jhubbard@...dia.com>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Gerald Schaefer <gerald.schaefer@...ibm.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Will Deacon <will@...nel.org>
Subject: Re: [PATCH v4 26/26] mm/gup: Remove task_struct pointer for all gup
 code

On Wed, Jul 01, 2020 at 02:55:40PM -0700, John Hubbard wrote:
> On 2020-06-30 13:46, Peter Xu wrote:
> > After the cleanup of page fault accounting, gup does not need to pass
> > task_struct around any more.  Remove that parameter in the whole gup stack.
> > 
> > Signed-off-by: Peter Xu <peterx@...hat.com>
> > ---
> >   arch/arc/kernel/process.c                   |  2 +-
> >   arch/s390/kvm/interrupt.c                   |  2 +-
> >   arch/s390/kvm/kvm-s390.c                    |  2 +-
> >   arch/s390/kvm/priv.c                        |  8 +-
> >   arch/s390/mm/gmap.c                         |  4 +-
> >   drivers/gpu/drm/i915/gem/i915_gem_userptr.c |  2 +-
> >   drivers/infiniband/core/umem_odp.c          |  2 +-
> >   drivers/vfio/vfio_iommu_type1.c             |  4 +-
> >   fs/exec.c                                   |  2 +-
> >   include/linux/mm.h                          |  9 +-
> >   kernel/events/uprobes.c                     |  6 +-
> >   kernel/futex.c                              |  2 +-
> >   mm/gup.c                                    | 92 +++++++++------------
> >   mm/memory.c                                 |  2 +-
> >   mm/process_vm_access.c                      |  2 +-
> >   security/tomoyo/domain.c                    |  2 +-
> >   virt/kvm/async_pf.c                         |  2 +-
> >   virt/kvm/kvm_main.c                         |  2 +-
> >   18 files changed, 65 insertions(+), 82 deletions(-)
> > 
> 
> Looks good:
> 
>     Reviewed-by: John Hubbard <jhubbard@...dia.com>
> 
> One minor refinement: in gup.c, if you add the following hunk on top of your
> changes, that will eradicate the last reference to struct task, in that file:
> 
> 
> diff --git a/mm/gup.c b/mm/gup.c
> index 8ddc48022d74..75c4b305828b 100644
> --- a/mm/gup.c
> +++ b/mm/gup.c
> @@ -1902,10 +1902,9 @@ static long __get_user_pages_remote(struct mm_struct *mm,
>   *              Or NULL if the caller does not require them.
>   *
>   * This is the same as get_user_pages_remote(), just with a
> - * less-flexible calling convention where we assume that the task
> - * and mm being operated on are the current task's and don't allow
> - * passing of a locked parameter.  We also obviously don't pass
> - * FOLL_REMOTE in here.
> + * less-flexible calling convention where we assume that the mm being operated
> + * on belongs to the current task, and doesn't allow passing of a locked
> + * parameter. We also obviously don't pass FOLL_REMOTE in here.
>   */
>  long get_user_pages(unsigned long start, unsigned long nr_pages,
>                 unsigned int gup_flags, struct page **pages,

Right.  Fixed it up, and with the r-b kept.  Thanks!

-- 
Peter Xu