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SubjectRe: [PATCH v2] orangefs: convert get_user_pages() --> pin_user_pages()
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On 2020-05-22 20:59, John Hubbard wrote:
> This code was using get_user_pages*(), in a "Case 1" scenario
> (Direct IO), 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/
>
> Cc: Mike Marshall <hubcap@omnibond.com>
> Cc: Martin Brandenburg <martin@omnibond.com>
> Cc: devel@lists.orangefs.org
> Cc: linux-fsdevel@vger.kernel.org
> Signed-off-by: John Hubbard <jhubbard@nvidia.com>
> ---
>
> Hi,
>
> Note that I have only compile-tested this patch, although that does
> also include cross-compiling for a few other arches.

An update on the run-time testing: Just now, I got basic orangefs tests
running in xfstests, with this patch applied, and it all looks normal.

thanks,
--
John Hubbard
NVIDIA

>
> Changes since v1 [3]: correct the commit description, so that
> it refers to "Case 1" instead of "Case 2".
>
>
> [3] https://lore.kernel.org/r/20200518060139.2828423-1-jhubbard@nvidia.com
>
> thanks,
> John Hubbard
> NVIDIA
>
> 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;
> }
>

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