f2fs: catch up to v4.14-rc1

Cherry-picked from upstream-f2fs-stable-linux-4.9.y

Changes include:

commit 30da3a4de96733 ("f2fs: hurry up to issue discard after io interruption")
commit d1c363b48398d4 ("f2fs: fix to show correct discard_granularity in sysfs")
...

commit e6b120d4d01ab0 ("f2fs/fscrypt: catch up to v4.12")
commit 4d7931d72758db ("KEYS: Differentiate uses of rcu_dereference_key() and user_key_payload()")

Signed-off-by: Hyojun Kim <hyojun@google.com>
diff --git a/Documentation/security/keys.txt b/Documentation/security/keys.txt
index 3849814..0e03baf 100644
--- a/Documentation/security/keys.txt
+++ b/Documentation/security/keys.txt
@@ -1151,8 +1151,21 @@
      usage.  This is called key->payload.rcu_data0.  The following accessors
      wrap the RCU calls to this element:
 
-	rcu_assign_keypointer(struct key *key, void *data);
-	void *rcu_dereference_key(struct key *key);
+     (a) Set or change the first payload pointer:
+
+		rcu_assign_keypointer(struct key *key, void *data);
+
+     (b) Read the first payload pointer with the key semaphore held:
+
+		[const] void *dereference_key_locked([const] struct key *key);
+
+	 Note that the return value will inherit its constness from the key
+	 parameter.  Static analysis will give an error if it things the lock
+	 isn't held.
+
+     (c) Read the first payload pointer with the RCU read lock held:
+
+		const void *dereference_key_rcu(const struct key *key);
 
 
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