blk-mq: split tag ->rqs[] into two

This is in preparation for having two sets of tags available. For
that we need a static index, and a dynamically assignable one.
Signed-off-by: Jens Axboe <axboe@fb.com>
Reviewed-by: Omar Sandoval <osandov@fb.com>

block/blk-mq-tag.c

@@ -290,11 +290,11 @@ int blk_mq_reinit_tagset(struct blk_mq_tag_set *set)
 		struct blk_mq_tags *tags = set->tags[i];
 
 		for (j = 0; j < tags->nr_tags; j++) {
-			if (!tags->rqs[j])
+			if (!tags->static_rqs[j])
 				continue;
 
 			ret = set->ops->reinit_request(set->driver_data,
-						tags->rqs[j]);
+						tags->static_rqs[j]);
 			if (ret)
 				goto out;
 		}

block/blk-mq-tag.h

@@ -16,6 +16,7 @@ struct blk_mq_tags {
 	struct sbitmap_queue breserved_tags;
 
 	struct request **rqs;
+	struct request **static_rqs;
 	struct list_head page_list;
 };
 

block/blk-mq.c

@@ -223,7 +223,7 @@ struct request *__blk_mq_alloc_request(struct blk_mq_alloc_data *data,
 
 	tag = blk_mq_get_tag(data);
 	if (tag != BLK_MQ_TAG_FAIL) {
-		rq = data->hctx->tags->rqs[tag];
+		rq = data->hctx->tags->static_rqs[tag];
 
 		if (blk_mq_tag_busy(data->hctx)) {
 			rq->rq_flags = RQF_MQ_INFLIGHT;
@@ -231,6 +231,7 @@ struct request *__blk_mq_alloc_request(struct blk_mq_alloc_data *data,
 		}
 
 		rq->tag = tag;
+		data->hctx->tags->rqs[tag] = rq;
 		blk_mq_rq_ctx_init(data->q, data->ctx, rq, op);
 		return rq;
 	}
@@ -1567,11 +1568,13 @@ void blk_mq_free_rqs(struct blk_mq_tag_set *set, struct blk_mq_tags *tags,
 		int i;
 
 		for (i = 0; i < tags->nr_tags; i++) {
-			if (!tags->rqs[i])
+			struct request *rq = tags->static_rqs[i];
+
+			if (!rq)
 				continue;
-			set->ops->exit_request(set->driver_data, tags->rqs[i],
+			set->ops->exit_request(set->driver_data, rq,
 						hctx_idx, i);
-			tags->rqs[i] = NULL;
+			tags->static_rqs[i] = NULL;
 		}
 	}
 
@@ -1591,6 +1594,8 @@ void blk_mq_free_rq_map(struct blk_mq_tags *tags)
 {
 	kfree(tags->rqs);
 	tags->rqs = NULL;
+	kfree(tags->static_rqs);
+	tags->static_rqs = NULL;
 
 	blk_mq_free_tags(tags);
 }
@@ -1616,6 +1621,15 @@ struct blk_mq_tags *blk_mq_alloc_rq_map(struct blk_mq_tag_set *set,
 		return NULL;
 	}
 
+	tags->static_rqs = kzalloc_node(nr_tags * sizeof(struct request *),
+				 GFP_NOIO | __GFP_NOWARN | __GFP_NORETRY,
+				 set->numa_node);
+	if (!tags->static_rqs) {
+		kfree(tags->rqs);
+		blk_mq_free_tags(tags);
+		return NULL;
+	}
+
 	return tags;
 }
 
@@ -1677,12 +1691,14 @@ int blk_mq_alloc_rqs(struct blk_mq_tag_set *set, struct blk_mq_tags *tags,
 		to_do = min(entries_per_page, depth - i);
 		left -= to_do * rq_size;
 		for (j = 0; j < to_do; j++) {
-			tags->rqs[i] = p;
+			struct request *rq = p;
+
+			tags->static_rqs[i] = rq;
 			if (set->ops->init_request) {
 				if (set->ops->init_request(set->driver_data,
-						tags->rqs[i], hctx_idx, i,
+						rq, hctx_idx, i,
 						set->numa_node)) {
-					tags->rqs[i] = NULL;
+					tags->static_rqs[i] = NULL;
 					goto fail;
 				}
 			}