This code was using get_user_pages_fast(), in a "Case 2" scenario
(DMA/RDMA), using the categorization from [1]. That means that it's
time to convert the get_user_pages_fast() + put_page() calls to
pin_user_pages_fast() + 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: David S. Miller <davem@xxxxxxxxxxxxx>
Cc: Jakub Kicinski <kuba@xxxxxxxxxx>
Cc: netdev@xxxxxxxxxxxxxxx
Cc: linux-rdma@xxxxxxxxxxxxxxx
Cc: rds-devel@xxxxxxxxxxxxxx
Signed-off-by: John Hubbard <jhubbard@xxxxxxxxxx>
---
net/rds/info.c | 6 ++----
1 file changed, 2 insertions(+), 4 deletions(-)
diff --git a/net/rds/info.c b/net/rds/info.c
index 03f6fd56d237..e1d63563e81c 100644
--- a/net/rds/info.c
+++ b/net/rds/info.c
@@ -162,7 +162,6 @@ int rds_info_getsockopt(struct socket *sock, int optname, char __user *optval,
struct rds_info_lengths lens;
unsigned long nr_pages = 0;
unsigned long start;
- unsigned long i;
rds_info_func func;
struct page **pages = NULL;
int ret;
@@ -193,7 +192,7 @@ int rds_info_getsockopt(struct socket *sock, int optname, char __user *optval,
ret = -ENOMEM;
goto out;
}
- ret = get_user_pages_fast(start, nr_pages, FOLL_WRITE, pages);
+ ret = pin_user_pages_fast(start, nr_pages, FOLL_WRITE, pages);
if (ret != nr_pages) {
if (ret > 0)
nr_pages = ret;
@@ -235,8 +234,7 @@ int rds_info_getsockopt(struct socket *sock, int optname, char __user *optval,
ret = -EFAULT;
out:
- for (i = 0; pages && i < nr_pages; i++)
- put_page(pages[i]);
+ unpin_user_pages(pages, nr_pages);
kfree(pages);
return ret;
base-commit: 3d1c1e5931ce45b3a3f309385bbc00c78e9951c6
--
2.26.2
