mempool: add @gfp_mask to mempool_create_node()

mempool_create_node() currently assumes %GFP_KERNEL.  Its only user,
blk_init_free_list(), is about to be updated to use other allocation
flags - add @gfp_mask argument to the function.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/block/blk-core.c b/block/blk-core.c
index 93eb3e4..64f9a86 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -531,8 +531,8 @@
 	init_waitqueue_head(&rl->wait[BLK_RW_ASYNC]);
 
 	rl->rq_pool = mempool_create_node(BLKDEV_MIN_RQ, mempool_alloc_slab,
-				mempool_free_slab, request_cachep, q->node);
-
+					  mempool_free_slab, request_cachep,
+					  GFP_KERNEL, q->node);
 	if (!rl->rq_pool)
 		return -ENOMEM;