mm: showmem: make the notifiers atomic

There are places in kernel like the lowmemorykiller which
invokes show_mem_call_notifiers from an atomic context.
So move from a blocking notifier to atomic. At present
the notifier callbacks does not call sleeping functions,
but it should be made sure, it does not happen in future also.

Change-Id: I9668e67463ab8a6a60be55dbc86b88f45be8b041
Signed-off-by: Vinayak Menon <vinmenon@codeaurora.org>
Signed-off-by: Patrick Daly <pdaly@codeaurora.org>
[swatsrid@codeaurora.org: Fix merge conflicts]
Signed-off-by: Swathi Sridhar <swatsrid@codeaurora.org>
diff --git a/mm/showmem.c b/mm/showmem.c
index a7e3caf..62bea47 100644
--- a/mm/showmem.c
+++ b/mm/showmem.c
@@ -9,21 +9,21 @@
 #include <linux/fs.h>
 #include <linux/init.h>
 
-BLOCKING_NOTIFIER_HEAD(show_mem_notifier);
+ATOMIC_NOTIFIER_HEAD(show_mem_notifier);
 
 int show_mem_notifier_register(struct notifier_block *nb)
 {
-	return blocking_notifier_chain_register(&show_mem_notifier, nb);
+	return atomic_notifier_chain_register(&show_mem_notifier, nb);
 }
 
 int show_mem_notifier_unregister(struct notifier_block *nb)
 {
-	return blocking_notifier_chain_unregister(&show_mem_notifier, nb);
+	return  atomic_notifier_chain_unregister(&show_mem_notifier, nb);
 }
 
 void show_mem_call_notifiers(void)
 {
-	blocking_notifier_call_chain(&show_mem_notifier, 0, NULL);
+	atomic_notifier_call_chain(&show_mem_notifier, 0, NULL);
 }
 
 static int show_mem_notifier_get(void *dat, u64 *val)