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Date:   Mon, 31 Jan 2022 09:36:49 -0400
From:   Jason Gunthorpe <jgg@ziepe.ca>
To:     John Hubbard <jhubbard@nvidia.com>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Peter Xu <peterx@redhat.com>, Jan Kara <jack@suse.cz>,
        Claudio Imbrenda <imbrenda@linux.ibm.com>,
        "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
        Alex Williamson <alex.williamson@redhat.com>,
        Andrea Arcangeli <aarcange@redhat.com>,
        =?utf-8?B?SsOpcsO0bWU=?= Glisse <jglisse@redhat.com>,
        LKML <linux-kernel@vger.kernel.org>, linux-mm@kvack.org
Subject: Re: [PATCH 2/4] mm/gup: clean up follow_pfn_pte() slightly
Message-ID: <20220131133649.GX8034@ziepe.ca>
References: <20220131051752.447699-1-jhubbard@nvidia.com>
 <20220131051752.447699-3-jhubbard@nvidia.com>
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On Sun, Jan 30, 2022 at 09:17:50PM -0800, John Hubbard wrote:
> Regardless of any FOLL_* flags, get_user_pages() and its variants should
> handle PFN-only entries by stopping early, if the caller expected
> **pages to be filled in.
> 
> This makes for a more reliable API, as compared to the previous approach
> of skipping over such entries (and thus leaving them silently
> unwritten).
> 
> Cc: Peter Xu <peterx@redhat.com>
> Suggested-by: Jason Gunthorpe <jgg@ziepe.ca>
> Signed-off-by: John Hubbard <jhubbard@nvidia.com>
> ---
>  mm/gup.c | 12 +++++++-----
>  1 file changed, 7 insertions(+), 5 deletions(-)

I still think it should be squashed into the previous path, but
otherwise

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

Jason