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SubjectRE: [PATCH v3] fpga: dfl: afu: convert get_user_pages() --> pin_user_pages()
Date
> -----Original Message-----
> From: John Hubbard <jhubbard@nvidia.com>
> Sent: Tuesday, May 26, 2020 6:18 AM
> To: LKML <linux-kernel@vger.kernel.org>
> Cc: John Hubbard <jhubbard@nvidia.com>; Xu, Yilun <yilun.xu@intel.com>;
> Wu, Hao <hao.wu@intel.com>; Moritz Fischer <mdf@kernel.org>; linux-
> fpga@vger.kernel.org
> Subject: [PATCH v3] fpga: dfl: afu: convert get_user_pages() -->
> pin_user_pages()
>
> 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_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/
>
> Cc: Xu Yilun <yilun.xu@intel.com>
> Cc: Wu Hao <hao.wu@intel.com>
> Cc: Moritz Fischer <mdf@kernel.org>
> Cc: linux-fpga@vger.kernel.org
> Signed-off-by: John Hubbard <jhubbard@nvidia.com>
> ---
>
> Hi,
>
> This is the same logical change as in v2, but it is applied to
> char-misc-next, in order to avoid a merge problem with Souptick's
> commit c9d7e3da1f3c ("fpga: dfl: afu: Corrected error handling levels
> <Souptick Joarder>")

Thanks a lot!

Acked-by: Wu Hao <hao.wu@intel.com>

Thanks
Hao

>
> thanks,
> John Hubbard
> NVIDIA
>
>
> drivers/fpga/dfl-afu-dma-region.c | 19 +++++--------------
> 1 file changed, 5 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/fpga/dfl-afu-dma-region.c b/drivers/fpga/dfl-afu-dma-
> region.c
> index 5942343a5d6e..0b817b722920 100644
> --- a/drivers/fpga/dfl-afu-dma-region.c
> +++ b/drivers/fpga/dfl-afu-dma-region.c
> @@ -16,15 +16,6 @@
>
> #include "dfl-afu.h"
>
> -static void put_all_pages(struct page **pages, int npages)
> -{
> - int i;
> -
> - for (i = 0; i < npages; i++)
> - if (pages[i])
> - put_page(pages[i]);
> -}
> -
> void afu_dma_region_init(struct dfl_feature_platform_data *pdata)
> {
> struct dfl_afu *afu = dfl_fpga_pdata_get_private(pdata);
> @@ -57,22 +48,22 @@ static int afu_dma_pin_pages(struct
> dfl_feature_platform_data *pdata,
> goto unlock_vm;
> }
>
> - pinned = get_user_pages_fast(region->user_addr, npages,
> FOLL_WRITE,
> + pinned = pin_user_pages_fast(region->user_addr, npages,
> FOLL_WRITE,
> region->pages);
> if (pinned < 0) {
> ret = pinned;
> goto free_pages;
> } else if (pinned != npages) {
> ret = -EFAULT;
> - goto put_pages;
> + goto unpin_pages;
> }
>
> dev_dbg(dev, "%d pages pinned\n", pinned);
>
> return 0;
>
> -put_pages:
> - put_all_pages(region->pages, pinned);
> +unpin_pages:
> + unpin_user_pages(region->pages, pinned);
> free_pages:
> kfree(region->pages);
> unlock_vm:
> @@ -94,7 +85,7 @@ static void afu_dma_unpin_pages(struct
> dfl_feature_platform_data *pdata,
> long npages = region->length >> PAGE_SHIFT;
> struct device *dev = &pdata->dev->dev;
>
> - put_all_pages(region->pages, npages);
> + unpin_user_pages(region->pages, npages);
> kfree(region->pages);
> account_locked_vm(current->mm, npages, false);
>
> --
> 2.26.2

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