Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
From:   "Huang, Ying" <ying.huang@intel.com>
To:     Andrew Morton <akpm@linux-foundation.org>
Cc:     linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        Huang Ying <ying.huang@intel.com>,
        Mike Kravetz <mike.kravetz@oracle.com>,
        Andrea Parri <andrea.parri@amarulasolutions.com>,
        "Paul E . McKenney" <paulmck@linux.vnet.ibm.com>,
        Michal Hocko <mhocko@suse.com>,
        Minchan Kim <minchan@kernel.org>,
        Hugh Dickins <hughd@google.com>
Subject: [PATCH -mm] mm, swap: Fix bad swap file entry warning
Date:   Fri, 31 May 2019 10:41:02 +0800
Message-Id: <20190531024102.21723-1-ying.huang@intel.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

From: Huang Ying <ying.huang@intel.com>

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" <ying.huang@intel.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Andrea Parri <andrea.parri@amarulasolutions.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Hugh Dickins <hughd@google.com>
---
 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