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    SubjectRe: [PATCH] staging: gasket: Convert get_user_pages*() --> pin_user_pages*()
    On Thu, May 28, 2020 at 4:34 PM Dan Carpenter <dan.carpenter@oracle.com> wrote:
    >
    > On Thu, May 28, 2020 at 02:32:42AM +0530, Souptick Joarder wrote:
    > > This code was using get_user_pages_fast(), in a "Case 2" scenario
    > > (DMA/RDMA), using the categorization from [1]. That means that it's
    > > time to convert the get_user_pages_fast() + put_page() calls to
    > > pin_user_pages_fast() + unpin_user_page() calls.
    >
    > You are saying that the page is used for DIO and not DMA, but it sure
    > looks to me like it is used for DMA.

    No, I was referring to "Case 2" scenario in change log which means it is
    used for DMA, not DIO.

    >
    > 503 /* Map the page into DMA space. */
    > 504 ptes[i].dma_addr =
    > 505 dma_map_page(pg_tbl->device, page, 0, PAGE_SIZE,
    > 506 DMA_BIDIRECTIONAL);
    >
    > To be honest, that starting paragraph was confusing. At first I thought
    > you were saying gasket was an RDMA driver. :P I shouldn't have to read
    > a different document to understand the commit message. It should be
    > summarized enough and the other documentation is supplemental.
    >
    > "In 2019 we introduced pin_user_pages() and now we are converting
    > get_user_pages() to the new API as appropriate".

    As all other similar conversion have similar change logs, so I was trying
    to maintain the same. John might have a different opinion on this.

    John, Any further opinion ??

    >
    > >
    > > There is some helpful background in [2]: basically, this is a small
    > > part of fixing a long-standing disconnect between pinning pages, and
    > > file systems' use of those pages.
    >
    > What is the impact of this patch on runtime?

    I don't have the hardware to validate the runtime impact and will
    wait if someone is going to validate it for runtime impact.

    >
    > >
    > > [1] Documentation/core-api/pin_user_pages.rst
    > >
    > > [2] "Explicit pinning of user-space pages":
    > > https://lwn.net/Articles/807108/
    > >
    > > Signed-off-by: Souptick Joarder <jrdr.linux@gmail.com>
    > > Cc: John Hubbard <jhubbard@nvidia.com>
    > >
    > > Hi,
    > >
    > > I'm compile tested this, but unable to run-time test, so any testing
    > > help is much appriciated.
    > > ---
    >
    > The "Hi" part of patch should have been under the "---" cut off line so
    > this will definitely need to be resent.

    Sorry about it.
    Will wait for feedback from John before resend it :)

    >
    > regards,
    > dan carpenter
    >

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