net: allow GFP_HIGHMEM in __vmalloc()

We forgot to use __GFP_HIGHMEM in several __vmalloc() calls.

In ceph, add the missing flag.

In fib_trie.c, xfrm_hash.c and request_sock.c, using vzalloc() is
cleaner and allows using HIGHMEM pages as well.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/core/request_sock.c b/net/core/request_sock.c
index 7552495..fceeb37 100644
--- a/net/core/request_sock.c
+++ b/net/core/request_sock.c
@@ -45,9 +45,7 @@
 	nr_table_entries = roundup_pow_of_two(nr_table_entries + 1);
 	lopt_size += nr_table_entries * sizeof(struct request_sock *);
 	if (lopt_size > PAGE_SIZE)
-		lopt = __vmalloc(lopt_size,
-			GFP_KERNEL | __GFP_HIGHMEM | __GFP_ZERO,
-			PAGE_KERNEL);
+		lopt = vzalloc(lopt_size);
 	else
 		lopt = kzalloc(lopt_size, GFP_KERNEL);
 	if (lopt == NULL)