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Date:   Wed, 16 Nov 2022 20:45:21 -0400
From:   Jason Gunthorpe <jgg@ziepe.ca>
To:     David Hildenbrand <david@redhat.com>
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        Alex Williamson <alex.williamson@redhat.com>,
        Leon Romanovsky <leonro@nvidia.com>,
        Leon Romanovsky <leon@kernel.org>
Subject: Re: [PATCH mm-unstable v1 10/20] RDMA/umem: remove FOLL_FORCE usage
Message-ID: <Y3WEIVROhUPTtaeQ@ziepe.ca>
References: <20221116102659.70287-1-david@redhat.com>
 <20221116102659.70287-11-david@redhat.com>
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On Wed, Nov 16, 2022 at 11:26:49AM +0100, David Hildenbrand wrote:
> GUP now supports reliable R/O long-term pinning in COW mappings, such
> that we break COW early. MAP_SHARED VMAs only use the shared zeropage so
> far in one corner case (DAXFS file with holes), which can be ignored
> because GUP does not support long-term pinning in fsdax (see
> check_vma_flags()).
> 
> Consequently, FOLL_FORCE | FOLL_WRITE | FOLL_LONGTERM is no longer required
> for reliable R/O long-term pinning: FOLL_LONGTERM is sufficient. So stop
> using FOLL_FORCE, which is really only for ptrace access.
> 
> Tested-by: Leon Romanovsky <leonro@nvidia.com> # Over mlx4 and mlx5.
> Cc: Jason Gunthorpe <jgg@ziepe.ca>
> Cc: Leon Romanovsky <leon@kernel.org>
> Signed-off-by: David Hildenbrand <david@redhat.com>
> ---
>  drivers/infiniband/core/umem.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)

Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>

Jason