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SubjectRe: [PATCH] drm/radeon: Convert get_user_pages() --> pin_user_pages()
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On 2020-05-26 14:00, Souptick Joarder wrote:
> This code was using get_user_pages(), in a "Case 2" scenario
> (DMA/RDMA), using the categorization from [1]. That means that it's
> time to convert the get_user_pages() + release_pages() calls to
> pin_user_pages() + unpin_user_pages() calls.
>
> 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.
>
> [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.
> ---
> drivers/gpu/drm/radeon/radeon_ttm.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/radeon/radeon_ttm.c b/drivers/gpu/drm/radeon/radeon_ttm.c
> index 5d50c9e..e927de2 100644
> --- a/drivers/gpu/drm/radeon/radeon_ttm.c
> +++ b/drivers/gpu/drm/radeon/radeon_ttm.c
> @@ -506,7 +506,7 @@ static int radeon_ttm_tt_pin_userptr(struct ttm_tt *ttm)
> uint64_t userptr = gtt->userptr + pinned * PAGE_SIZE;
> struct page **pages = ttm->pages + pinned;
>
> - r = get_user_pages(userptr, num_pages, write ? FOLL_WRITE : 0,
> + r = pin_user_pages(userptr, num_pages, write ? FOLL_WRITE : 0,
> pages, NULL);
> if (r < 0)
> goto release_pages;
> @@ -535,7 +535,7 @@ static int radeon_ttm_tt_pin_userptr(struct ttm_tt *ttm)
> kfree(ttm->sg);
>
> release_pages:
> - release_pages(ttm->pages, pinned);
> + unpin_user_pages(ttm->pages, pinned);
> return r;
> }
>
> @@ -562,7 +562,7 @@ static void radeon_ttm_tt_unpin_userptr(struct ttm_tt *ttm)
> set_page_dirty(page);


Maybe we also need a preceding patch, to fix the above? It should be
set_page_dirty_lock(), rather than set_page_dirty(), unless I'm overlooking
something (which is very possible!).

Either way, from a tunnel vision perspective of changing gup to pup, this
looks good to me, so

Acked-by: John Hubbard <jhubbard@nvidia.com>


thanks,
--
John Hubbard
NVIDIA

>
> mark_page_accessed(page);
> - put_page(page);
> + unpin_user_page(page);
> }
>
> sg_free_table(ttm->sg);
>

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