mm/swap_slots.c: add warning if swap slots cache failed to initialize

Add a warning diagnostics to user if we failed to allocate swap slots
cache and use it.

[akpm@linux-foundation.org: use WARN_ONCE return value, fix grammar in message]
Link: http://lkml.kernel.org/r/20170328234827.GA10107@linux.intel.com
Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 3 insertions, 1 deletions

diff --git a/mm/swap_slots.c b/mm/swap_slots.c
index b1ccb58ad397..aa1c415f4abd 100644
--- a/mm/swap_slots.c
+++ b/mm/swap_slots.c
@@ -241,8 +241,10 @@ int enable_swap_slots_cache(void)
 
         ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "swap_slots_cache",
                                 alloc_swap_slot_cache, free_slot_cache);
-        if (ret < 0)
+        if (WARN_ONCE(ret < 0, "Cache allocation failed (%s), operating "
+                               "without swap slots cache.\n", __func__))
                 goto out_unlock;
+
         swap_slot_cache_initialized = true;
         __reenable_swap_slots_cache();
 out_unlock: