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    Subject[PATCH v9 11/25] goldish_pipe: convert to pin_user_pages() and put_user_page()
    Date
    1. Call the new global pin_user_pages_fast(), from pin_goldfish_pages().

    2. As required by pin_user_pages(), release these pages via
    put_user_page(). In this case, do so via put_user_pages_dirty_lock().

    That has the side effect of calling set_page_dirty_lock(), instead
    of set_page_dirty(). This is probably more accurate.

    As Christoph Hellwig put it, "set_page_dirty() is only safe if we are
    dealing with a file backed page where we have reference on the inode it
    hangs off." [1]

    Another side effect is that the release code is simplified because
    the page[] loop is now in gup.c instead of here, so just delete the
    local release_user_pages() entirely, and call
    put_user_pages_dirty_lock() directly, instead.

    [1] https://lore.kernel.org/r/20190723153640.GB720@lst.de

    Reviewed-by: Jan Kara <jack@suse.cz>
    Reviewed-by: Ira Weiny <ira.weiny@intel.com>
    Signed-off-by: John Hubbard <jhubbard@nvidia.com>
    ---
    drivers/platform/goldfish/goldfish_pipe.c | 17 +++--------------
    1 file changed, 3 insertions(+), 14 deletions(-)

    diff --git a/drivers/platform/goldfish/goldfish_pipe.c b/drivers/platform/goldfish/goldfish_pipe.c
    index ef50c264db71..2a5901efecde 100644
    --- a/drivers/platform/goldfish/goldfish_pipe.c
    +++ b/drivers/platform/goldfish/goldfish_pipe.c
    @@ -274,7 +274,7 @@ static int goldfish_pin_pages(unsigned long first_page,
    *iter_last_page_size = last_page_size;
    }

    - ret = get_user_pages_fast(first_page, requested_pages,
    + ret = pin_user_pages_fast(first_page, requested_pages,
    !is_write ? FOLL_WRITE : 0,
    pages);
    if (ret <= 0)
    @@ -285,18 +285,6 @@ static int goldfish_pin_pages(unsigned long first_page,
    return ret;
    }

    -static void release_user_pages(struct page **pages, int pages_count,
    - int is_write, s32 consumed_size)
    -{
    - int i;
    -
    - for (i = 0; i < pages_count; i++) {
    - if (!is_write && consumed_size > 0)
    - set_page_dirty(pages[i]);
    - put_page(pages[i]);
    - }
    -}
    -
    /* Populate the call parameters, merging adjacent pages together */
    static void populate_rw_params(struct page **pages,
    int pages_count,
    @@ -372,7 +360,8 @@ static int transfer_max_buffers(struct goldfish_pipe *pipe,

    *consumed_size = pipe->command_buffer->rw_params.consumed_size;

    - release_user_pages(pipe->pages, pages_count, is_write, *consumed_size);
    + put_user_pages_dirty_lock(pipe->pages, pages_count,
    + !is_write && *consumed_size > 0);

    mutex_unlock(&pipe->lock);
    return 0;
    --
    2.24.0
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