[PATCH] orangefs: convert get_user_pages() --> pin_user_pages()

[PATCH] orangefs: convert get_user_pages() --> pin_user_pages()

[John Hubbard]

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*() + put_page() 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: John Hubbard <jhubbard@nvidia.com>
---

 fs/orangefs/orangefs-bufmap.c | 9 +++------
 1 file changed, 3 insertions(+), 6 deletions(-)

diff --git a/fs/orangefs/orangefs-bufmap.c b/fs/orangefs/orangefs-bufmap.c
index 2bb916d68576..538e839590ef 100644
--- a/fs/orangefs/orangefs-bufmap.c
+++ b/fs/orangefs/orangefs-bufmap.c
@@ -168,10 +168,7 @@ static DEFINE_SPINLOCK(orangefs_bufmap_lock);
 static void
 orangefs_bufmap_unmap(struct orangefs_bufmap *bufmap)
 {
-	int i;
-
-	for (i = 0; i < bufmap->page_count; i++)
-		put_page(bufmap->page_array[i]);
+	unpin_user_pages(bufmap->page_array, bufmap->page_count);
 }
 
 static void
@@ -268,7 +265,7 @@ orangefs_bufmap_map(struct orangefs_bufmap *bufmap,
 	int offset = 0, ret, i;
 
 	/* map the pages */
-	ret = get_user_pages_fast((unsigned long)user_desc->ptr,
+	ret = pin_user_pages_fast((unsigned long)user_desc->ptr,
 			     bufmap->page_count, FOLL_WRITE, bufmap->page_array);
 
 	if (ret < 0)
@@ -280,7 +277,7 @@ orangefs_bufmap_map(struct orangefs_bufmap *bufmap,
 
 		for (i = 0; i < ret; i++) {
 			SetPageError(bufmap->page_array[i]);
-			put_page(bufmap->page_array[i]);
+			unpin_user_page(bufmap->page_array[i]);
 		}
 		return -ENOMEM;
 	}
-- 
2.26.2

Re: [PATCH] orangefs: convert get_user_pages() --> pin_user_pages()

[John Hubbard]

On 2020-05-17 23:01, John Hubbard 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*() + put_page() calls to
> pin_user_pages*() + unpin_user_pages() calls.

Oops, actually, maybe that description is wrong. This is probably
closer to "Case 1: Direct IO"...right? I don't see an O_DIRECT
anywhere, but there is an ioctl to do ORANGEFS_DEV_MAP, which seems
like effectively it's doing Direct IO.

(I got lulled into commit log complacency, due to sending quite a few
non-filesystem patches that were Case 2.)


thanks,
-- 
John Hubbard
NVIDIA

> 
> 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: John Hubbard <jhubbard@nvidia.com>
> ---
> 
>   fs/orangefs/orangefs-bufmap.c | 9 +++------
>   1 file changed, 3 insertions(+), 6 deletions(-)
> 
> diff --git a/fs/orangefs/orangefs-bufmap.c b/fs/orangefs/orangefs-bufmap.c
> index 2bb916d68576..538e839590ef 100644
> --- a/fs/orangefs/orangefs-bufmap.c
> +++ b/fs/orangefs/orangefs-bufmap.c
> @@ -168,10 +168,7 @@ static DEFINE_SPINLOCK(orangefs_bufmap_lock);
>   static void
>   orangefs_bufmap_unmap(struct orangefs_bufmap *bufmap)
>   {
> -	int i;
> -
> -	for (i = 0; i < bufmap->page_count; i++)
> -		put_page(bufmap->page_array[i]);
> +	unpin_user_pages(bufmap->page_array, bufmap->page_count);
>   }
>   
>   static void
> @@ -268,7 +265,7 @@ orangefs_bufmap_map(struct orangefs_bufmap *bufmap,
>   	int offset = 0, ret, i;
>   
>   	/* map the pages */
> -	ret = get_user_pages_fast((unsigned long)user_desc->ptr,
> +	ret = pin_user_pages_fast((unsigned long)user_desc->ptr,
>   			     bufmap->page_count, FOLL_WRITE, bufmap->page_array);
>   
>   	if (ret < 0)
> @@ -280,7 +277,7 @@ orangefs_bufmap_map(struct orangefs_bufmap *bufmap,
>   
>   		for (i = 0; i < ret; i++) {
>   			SetPageError(bufmap->page_array[i]);
> -			put_page(bufmap->page_array[i]);
> +			unpin_user_page(bufmap->page_array[i]);
>   		}
>   		return -ENOMEM;
>   	}
>