[RFC PATCH] xen/gntdev.c: Convert get_user_pages*() to pin_user_pages*()

From: Souptick Joarder
Date: Tue Aug 18 2020 - 00:23:58 EST


In 2019, we introduced pin_user_pages*() and now we are converting
get_user_pages*() to the new API as appropriate. [1] & [2] could
be referred for more information. This is case 5 as per document [1].

[1] Documentation/core-api/pin_user_pages.rst

[2] "Explicit pinning of user-space pages":
https://lwn.net/Articles/807108/

Signed-off-by: Souptick Joarder <jrdr.linux@xxxxxxxxx>
Cc: John Hubbard <jhubbard@xxxxxxxxxx>
---
drivers/xen/gntdev.c | 7 ++-----
1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c
index 64a9025a..e480509 100644
--- a/drivers/xen/gntdev.c
+++ b/drivers/xen/gntdev.c
@@ -730,7 +730,7 @@ static int gntdev_get_page(struct gntdev_copy_batch *batch, void __user *virt,
unsigned long xen_pfn;
int ret;

- ret = get_user_pages_fast(addr, 1, writeable ? FOLL_WRITE : 0, &page);
+ ret = pin_user_pages_fast(addr, 1, writeable ? FOLL_WRITE : 0, &page);
if (ret < 0)
return ret;

@@ -744,10 +744,7 @@ static int gntdev_get_page(struct gntdev_copy_batch *batch, void __user *virt,

static void gntdev_put_pages(struct gntdev_copy_batch *batch)
{
- unsigned int i;
-
- for (i = 0; i < batch->nr_pages; i++)
- put_page(batch->pages[i]);
+ unpin_user_pages(batch->pages, batch->nr_pages);
batch->nr_pages = 0;
}

--
1.9.1