[net-next][PATCH v2 1/2] rds: handle unsupported rdma request to fs dax memory

[Santosh Shilimkar <santosh.shilimkar@oracle.com>]

From: Hans Westgaard Ry <hans.westgaard.ry@oracle.com>

RDS doesn't support RDMA on memory apertures that require On Demand
Paging (ODP), such as FS DAX memory. User applications can try to use
RDS to perform RDMA over such memories and since it doesn't report any
failure, it can lead to unexpected issues like memory corruption when
a couple of out of sync file system operations like ftruncate etc. are
performed.

The patch adds a check so that such an attempt to RDMA to/from memory
apertures requiring ODP will fail.

Reviewed-by: Håkon Bugge <haakon.bugge@oracle.com>
Reviewed-tested-by: Zhu Yanjun <yanjun.zhu@oracle.com>
Signed-off-by: Hans Westgaard Ry <hans.westgaard.ry@oracle.com>
Signed-off-by: Santosh Shilimkar <santosh.shilimkar@oracle.com>
---
 net/rds/rdma.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/net/rds/rdma.c b/net/rds/rdma.c
index 182ab84..e0a6b72 100644
--- a/net/rds/rdma.c
+++ b/net/rds/rdma.c
@@ -158,8 +158,9 @@ static int rds_pin_pages(unsigned long user_addr, unsigned int nr_pages,
 {
 	int ret;
 
-	ret = get_user_pages_fast(user_addr, nr_pages, write, pages);
-
+	/* get_user_pages return -EOPNOTSUPP for fs_dax memory */
+	ret = get_user_pages_longterm(user_addr, nr_pages,
+				      write, pages, NULL);
 	if (ret >= 0 && ret < nr_pages) {
 		while (ret--)
 			put_page(pages[ret]);
-- 
1.9.1