From: Huang Ying <[email protected]>

Mike reported the following warning messages

  get_swap_device: Bad swap file entry 1400000000000001

This is produced by

- total_swapcache_pages()
  - get_swap_device()

Where get_swap_device() is used to check whether the swap device is
valid and prevent it from being swapoff if so.  But get_swap_device()
may produce warning message as above for some invalid swap devices.
This is fixed via calling swp_swap_info() before get_swap_device() to
filter out the swap devices that may cause warning messages.

Fixes: 6a946753dbe6 ("mm/swap_state.c: simplify total_swapcache_pages() with 
get_swap_device()")
Signed-off-by: "Huang, Ying" <[email protected]>
Cc: Mike Kravetz <[email protected]>
Cc: Andrea Parri <[email protected]>
Cc: Paul E. McKenney <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Minchan Kim <[email protected]>
Cc: Hugh Dickins <[email protected]>
---
 mm/swap_state.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/mm/swap_state.c b/mm/swap_state.c
index b84c58b572ca..62da25b7f2ed 100644
--- a/mm/swap_state.c
+++ b/mm/swap_state.c
@@ -76,8 +76,13 @@ unsigned long total_swapcache_pages(void)
        struct swap_info_struct *si;
 
        for (i = 0; i < MAX_SWAPFILES; i++) {
+               swp_entry_t entry = swp_entry(i, 1);
+
+               /* Avoid get_swap_device() to warn for bad swap entry */
+               if (!swp_swap_info(entry))
+                       continue;
                /* Prevent swapoff to free swapper_spaces */
-               si = get_swap_device(swp_entry(i, 1));
+               si = get_swap_device(entry);
                if (!si)
                        continue;
                nr = nr_swapper_spaces[i];
-- 
2.20.1

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