blk-mq: change gfp flags to GFP_NOIO in blk_mq_realloc_hw_ctxs

blk_mq_realloc_hw_ctxs could be invoked during update hw queues.
At the momemt, IO is blocked. Change the gfp flags from GFP_KERNEL
to GFP_NOIO to avoid forever hang during memory allocation in
blk_mq_realloc_hw_ctxs.

Signed-off-by: Jianchao Wang <jianchao.w.wang@oracle.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/block/blk-flush.c b/block/blk-flush.c
index ce41f66..8b44b86 100644
--- a/block/blk-flush.c
+++ b/block/blk-flush.c
@@ -566,12 +566,12 @@ int blkdev_issue_flush(struct block_device *bdev, gfp_t gfp_mask,
 EXPORT_SYMBOL(blkdev_issue_flush);
 
 struct blk_flush_queue *blk_alloc_flush_queue(struct request_queue *q,
-		int node, int cmd_size)
+		int node, int cmd_size, gfp_t flags)
 {
 	struct blk_flush_queue *fq;
 	int rq_sz = sizeof(struct request);
 
-	fq = kzalloc_node(sizeof(*fq), GFP_KERNEL, node);
+	fq = kzalloc_node(sizeof(*fq), flags, node);
 	if (!fq)
 		goto fail;
 
@@ -579,7 +579,7 @@ struct blk_flush_queue *blk_alloc_flush_queue(struct request_queue *q,
 		spin_lock_init(&fq->mq_flush_lock);
 
 	rq_sz = round_up(rq_sz + cmd_size, cache_line_size());
-	fq->flush_rq = kzalloc_node(rq_sz, GFP_KERNEL, node);
+	fq->flush_rq = kzalloc_node(rq_sz, flags, node);
 	if (!fq->flush_rq)
 		goto fail_rq;