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: Wu Hao <[email protected]>
Cc: Moritz Fischer <[email protected]>
Cc: [email protected]
Signed-off-by: John Hubbard <[email protected]>
---
drivers/fpga/dfl-afu-dma-region.c | 15 +++------------
1 file changed, 3 insertions(+), 12 deletions(-)
diff --git a/drivers/fpga/dfl-afu-dma-region.c b/drivers/fpga/dfl-afu-dma-region.c
index 62f924489db5..84f696d5ba82 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);
@@ -57,7 +48,7 @@ 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;
@@ -72,7 +63,7 @@ static int afu_dma_pin_pages(struct dfl_feature_platform_data *pdata,
return 0;
put_pages:
- put_all_pages(region->pages, pinned);
+ 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);
base-commit: 3d1c1e5931ce45b3a3f309385bbc00c78e9951c6
--
2.26.2
On Sat, May 16, 2020 at 06:18:37PM -0700, John Hubbard 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_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: Wu Hao <[email protected]>
> Cc: Moritz Fischer <[email protected]>
> Cc: [email protected]
> Signed-off-by: John Hubbard <[email protected]>
> ---
> drivers/fpga/dfl-afu-dma-region.c | 15 +++------------
> 1 file changed, 3 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/fpga/dfl-afu-dma-region.c b/drivers/fpga/dfl-afu-dma-region.c
> index 62f924489db5..84f696d5ba82 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);
> @@ -57,7 +48,7 @@ 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;
> @@ -72,7 +63,7 @@ static int afu_dma_pin_pages(struct dfl_feature_platform_data *pdata,
> return 0;
>
> put_pages:
How about we also change the tag to "unpin_pages"?
Others look good to me.
Thanks,
Yilun.
> - put_all_pages(region->pages, pinned);
> + 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);
>
>
> base-commit: 3d1c1e5931ce45b3a3f309385bbc00c78e9951c6
> --
> 2.26.2
On 2020-05-19 08:10, Xu Yilun wrote:
...
>> @@ -72,7 +63,7 @@ static int afu_dma_pin_pages(struct dfl_feature_platform_data *pdata,
>> return 0;
>>
>> put_pages:
>
> How about we also change the tag to "unpin_pages"?
>
> Others look good to me.
>
Sure, I'll send a v2 with that.
thanks,
--
John Hubbard
NVIDIA