[RFC PATCH] xen/privcmd: Convert get_user_pages*() to pin_user_pages*()

[Souptick Joarder <jrdr.linux@xxxxxxxxx>]

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.

[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>
---
Hi,

I have compile tested this patch but unable to run-time test,
so any testing help is much appriciated.

Also have a question, why the existing code is not marking the
pages dirty (since it did FOLL_WRITE) ?

 drivers/xen/privcmd.c | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/drivers/xen/privcmd.c b/drivers/xen/privcmd.c
index a250d11..543739e 100644
--- a/drivers/xen/privcmd.c
+++ b/drivers/xen/privcmd.c
@@ -594,7 +594,7 @@ static int lock_pages(
                if (requested > nr_pages)
                        return -ENOSPC;
 
-               pinned = get_user_pages_fast(
+               pinned = pin_user_pages_fast(
                        (unsigned long) kbufs[i].uptr,
                        requested, FOLL_WRITE, pages);
                if (pinned < 0)
@@ -614,10 +614,7 @@ static void unlock_pages(struct page *pages[], unsigned 
int nr_pages)
        if (!pages)
                return;
 
-       for (i = 0; i < nr_pages; i++) {
-               if (pages[i])
-                       put_page(pages[i]);
-       }
+       unpin_user_pages(pages, nr_pages);
 }
 
 static long privcmd_ioctl_dm_op(struct file *file, void __user *udata)
-- 
1.9.1