[PATCH v2 20/34] xen: convert put_page() to put_user_page*()

john.hubbard
2019-08-04T22:53:10Z

This also handles pages[i] == NULL cases, thanks to an approach
that is actually written by Juergen Gross.

Signed-off-by: Juergen Gross <jgross@suse.com>
Signed-off-by: John Hubbard <jhubbard@nvidia.com>

Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: xen-devel@lists.xenproject.org
---

Hi Juergen,

Say, this is *exactly* what you proposed in your gup.patch, so
I've speculatively added your Signed-off-by above, but need your
approval before that's final. Let me know please...

thanks,
John Hubbard

drivers/xen/privcmd.c | 32 +++++++++++---------------------
1 file changed, 11 insertions(+), 21 deletions(-)

diff --git a/drivers/xen/privcmd.c b/drivers/xen/privcmd.c
index c6070e70dd73..c7d0763ca8c2 100644
--- a/drivers/xen/privcmd.c
+++ b/drivers/xen/privcmd.c
@@ -582,10 +582,11 @@ static long privcmd_ioctl_mmap_batch(

static int lock_pages(
struct privcmd_dm_op_buf kbufs[], unsigned int num,
- struct page *pages[], unsigned int nr_pages)
+ struct page *pages[], unsigned int *nr_pages)
{
- unsigned int i;
+ unsigned int i, free = *nr_pages;

+ *nr_pages = 0;
for (i = 0; i < num; i++) {
unsigned int requested;
int pinned;
@@ -593,35 +594,22 @@ static int lock_pages(
requested = DIV_ROUND_UP(
offset_in_page(kbufs[i].uptr) + kbufs[i].size,
PAGE_SIZE);
- if (requested > nr_pages)
+ if (requested > free)
return -ENOSPC;

pinned = get_user_pages_fast(
(unsigned long) kbufs[i].uptr,
- requested, FOLL_WRITE, pages);
+ requested, FOLL_WRITE, pages + *nr_pages);
if (pinned < 0)
return pinned;

- nr_pages -= pinned;
- pages += pinned;
+ free -= pinned;
+ *nr_pages += pinned;
}

return 0;
}

-static void unlock_pages(struct page *pages[], unsigned int nr_pages)
-{
- unsigned int i;
-
- if (!pages)
- return;
-
- for (i = 0; i < nr_pages; i++) {
- if (pages[i])
- put_page(pages[i]);
- }
-}
-
static long privcmd_ioctl_dm_op(struct file *file, void __user *udata)
{
struct privcmd_data *data = file->private_data;
@@ -681,11 +669,12 @@ static long privcmd_ioctl_dm_op(struct file *file, void __user *udata)

xbufs = kcalloc(kdata.num, sizeof(*xbufs), GFP_KERNEL);
if (!xbufs) {
+ nr_pages = 0;
rc = -ENOMEM;
goto out;
}

- rc = lock_pages(kbufs, kdata.num, pages, nr_pages);
+ rc = lock_pages(kbufs, kdata.num, pages, &nr_pages);
if (rc)
goto out;

@@ -699,7 +688,8 @@ static long privcmd_ioctl_dm_op(struct file *file, void __user *udata)
xen_preemptible_hcall_end();

out:
- unlock_pages(pages, nr_pages);
+ if (pages)
+ put_user_pages(pages, nr_pages);
kfree(xbufs);
kfree(pages);
kfree(kbufs);
--
2.22.0