[PATCH] shmem_swapin_page(): fix error processing for get_swap_device()

[Huang Ying]

Firstly, "-" is missing before the error code.  Secondly, EINVAL isn't
the proper error code for the race condition.  EEXIST is used in
shmem_swapin_page() for that.  So the error code is changed to EEXIST
too.

Link: https://lkml.kernel.org/r/20210723080000.93953-1-ying.huang@xxxxxxxxx
Fixes: 2efa33fc7f6e ("mm/shmem: fix shmem_swapin() race with swapoff")
Signed-off-by: "Huang, Ying" <ying.huang@xxxxxxxxx>
Cc: Miaohe Lin <linmiaohe@xxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Minchan Kim <minchan@xxxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
---
 mm/shmem.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/mm/shmem.c b/mm/shmem.c
index dcc07d14162e..ba925baa4404 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1711,8 +1711,8 @@ static int shmem_swapin_page(struct inode *inode, pgoff_t index,
 	/* Prevent swapoff from happening to us. */
 	si = get_swap_device(swap);
 	if (!si) {
-		error = EINVAL;
-		goto failed;
+		error = -EEXIST;
+		goto unlock;
 	}
 	/* Look it up and read it in.. */
 	page = lookup_swap_cache(swap, NULL, 0);
-- 
2.30.2