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fpga: dfl: afu: convert get_user_pages() --> pin_user_pages()

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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>
Acked-by: Wu Hao <hao.wu@intel.com>
Signed-off-by: Moritz Fischer <mdf@kernel.org>
This commit is contained in:
John Hubbard 2020-05-25 15:17:54 -07:00 committed by Moritz Fischer
parent b3a9e3b962
commit 55dc9b87e4
1 changed files with 5 additions and 14 deletions
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19
drivers/fpga/dfl-afu-dma-region.c
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@ -16,15 +16,6 @@
#include "dfl-afu.h" #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) void afu_dma_region_init(struct dfl_feature_platform_data *pdata)
{ {
struct dfl_afu *afu = dfl_fpga_pdata_get_private(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; 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); region->pages);
if (pinned < 0) { if (pinned < 0) {
ret = pinned; ret = pinned;
goto free_pages; goto free_pages;
} else if (pinned != npages) { } else if (pinned != npages) {
ret = -EFAULT; ret = -EFAULT;
goto put_pages; goto unpin_pages;
} }
dev_dbg(dev, "%d pages pinned\n", pinned); dev_dbg(dev, "%d pages pinned\n", pinned);
return 0; return 0;
put_pages: unpin_pages:
put_all_pages(region->pages, pinned); unpin_user_pages(region->pages, pinned);
free_pages: free_pages:
kfree(region->pages); kfree(region->pages);
unlock_vm: unlock_vm:
@ -94,7 +85,7 @@ static void afu_dma_unpin_pages(struct dfl_feature_platform_data *pdata,
long npages = region->length >> PAGE_SHIFT; long npages = region->length >> PAGE_SHIFT;
struct device *dev = &pdata->dev->dev; struct device *dev = &pdata->dev->dev;
put_all_pages(region->pages, npages); unpin_user_pages(region->pages, npages);
kfree(region->pages); kfree(region->pages);
account_locked_vm(current->mm, npages, false); account_locked_vm(current->mm, npages, false);