linux-kernel - Re: [PATCH v2 05/26] mm: gup: allow VM_FAULT

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Date:   Fri, 22 Feb 2019 10:13:22 -0500
From:   Jerome Glisse <jglisse@...hat.com>
To:     Peter Xu <peterx@...hat.com>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        David Hildenbrand <david@...hat.com>,
        Hugh Dickins <hughd@...gle.com>,
        Maya Gokhale <gokhale2@...l.gov>,
        Pavel Emelyanov <xemul@...tuozzo.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Martin Cracauer <cracauer@...s.org>, Shaohua Li <shli@...com>,
        Marty McFadden <mcfadden8@...l.gov>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Denis Plotnikov <dplotnikov@...tuozzo.com>,
        Mike Rapoport <rppt@...ux.vnet.ibm.com>,
        Mel Gorman <mgorman@...e.de>,
        "Kirill A . Shutemov" <kirill@...temov.name>,
        "Dr . David Alan Gilbert" <dgilbert@...hat.com>
Subject: Re: [PATCH v2 05/26] mm: gup: allow VM_FAULT_RETRY for multiple times

On Fri, Feb 22, 2019 at 12:41:05PM +0800, Peter Xu wrote:
> On Thu, Feb 21, 2019 at 11:06:55AM -0500, Jerome Glisse wrote:
> > On Tue, Feb 12, 2019 at 10:56:11AM +0800, Peter Xu wrote:
> > > This is the gup counterpart of the change that allows the VM_FAULT_RETRY
> > > to happen for more than once.
> > > 
> > > Signed-off-by: Peter Xu <peterx@...hat.com>
> > 
> > Reviewed-by: Jérôme Glisse <jglisse@...hat.com>
> 
> Thanks for the r-b, Jerome!
> 
> Though I plan to change this patch a bit because I just noticed that I
> didn't touch up the hugetlbfs path for GUP.  Though it was not needed
> for now because hugetlbfs is not yet supported but I think maybe I'd
> better do that as well in this same patch to make follow up works
> easier on hugetlb, and the patch will be more self contained.  The new
> version will simply squash below change into current patch:
> 
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index e3c738bde72e..a8eace2d5296 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -4257,8 +4257,10 @@ long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
>                                 fault_flags |= FAULT_FLAG_ALLOW_RETRY |
>                                         FAULT_FLAG_RETRY_NOWAIT;
>                         if (flags & FOLL_TRIED) {
> -                               VM_WARN_ON_ONCE(fault_flags &
> -                                               FAULT_FLAG_ALLOW_RETRY);
> +                               /*
> +                                * Note: FAULT_FLAG_ALLOW_RETRY and
> +                                * FAULT_FLAG_TRIED can co-exist
> +                                */
>                                 fault_flags |= FAULT_FLAG_TRIED;
>                         }
>                         ret = hugetlb_fault(mm, vma, vaddr, fault_flags);
> 
> I'd say this change is straightforward (it's the same as the
> faultin_page below but just for hugetlbfs).  Please let me know if you
> still want to offer the r-b with above change squashed (I'll be more
> than glad to take it!), or I'll just wait for your review comment when
> I post the next version.

Looks good i should have thought of hugetlbfs. You can keep my r-b.

Cheers,
Jérôme