blk-mq: simplify reallocation of hw ctxs a bit

blk_mq_alloc_and_init_hctx() has already taken reuse into account, so
no need to do it outside, then we can simplify blk_mq_realloc_hw_ctxs().

Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20220308073219.91173-3-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Author: Ming Lei

block/blk-mq.c

@@ -3966,29 +3966,24 @@ static void blk_mq_realloc_hw_ctxs(struct blk_mq_tag_set *set,
 	/* protect against switching io scheduler  */
 	mutex_lock(&q->sysfs_lock);
 	for (i = 0; i < set->nr_hw_queues; i++) {
+		int old_node;
 		int node = blk_mq_get_hctx_node(set, i);
-		struct blk_mq_hw_ctx *hctx;
+		struct blk_mq_hw_ctx *old_hctx = hctxs[i];
 
-		/*
-		 * If the hw queue has been mapped to another numa node,
-		 * we need to realloc the hctx. If allocation fails, fallback
-		 * to use the previous one.
-		 */
-		if (hctxs[i] && (hctxs[i]->numa_node == node))
-			continue;
+		if (old_hctx) {
+			old_node = old_hctx->numa_node;
+			blk_mq_exit_hctx(q, set, old_hctx, i);
+		}
 
-		hctx = blk_mq_alloc_and_init_hctx(set, q, i, node);
-		if (hctx) {
-			if (hctxs[i])
-				blk_mq_exit_hctx(q, set, hctxs[i], i);
-			hctxs[i] = hctx;
-		} else {
-			if (hctxs[i])
-				pr_warn("Allocate new hctx on node %d fails,\
-						fallback to previous one on node %d\n",
-						node, hctxs[i]->numa_node);
-			else
+		hctxs[i] = blk_mq_alloc_and_init_hctx(set, q, i, node);
+		if (!hctxs[i]) {
+			if (!old_hctx)
 				break;
+			pr_warn("Allocate new hctx on node %d fails, fallback to previous one on node %d\n",
+					node, old_node);
+			hctxs[i] = blk_mq_alloc_and_init_hctx(set, q, i,
+					old_node);
+			WARN_ON_ONCE(!hctxs[i]);
 		}
 	}
 	/*