block: don't allow writing to the poll queue attribute

The poll attribute is a historic artefact from before when we had
explicit poll queues that require driver specific configuration.
Just print a warning when writing to the attribute.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Tested-by: Mark Wunderlich <mark.wunderlich@intel.com>
Link: https://lore.kernel.org/r/20211012111226.760968-16-hch@lst.deSigned-off-by: Jens Axboe <axboe@kernel.dk>

block/blk-sysfs.c

@@ -433,26 +433,11 @@ static ssize_t queue_poll_show(struct request_queue *q, char *page)
 static ssize_t queue_poll_store(struct request_queue *q, const char *page,
 				size_t count)
 {
-	unsigned long poll_on;
-	ssize_t ret;
-
-	if (!q->tag_set || q->tag_set->nr_maps <= HCTX_TYPE_POLL ||
-	    !q->tag_set->map[HCTX_TYPE_POLL].nr_queues)
+	if (!test_bit(QUEUE_FLAG_POLL, &q->queue_flags))
 		return -EINVAL;
-
-	ret = queue_var_store(&poll_on, page, count);
-	if (ret < 0)
-		return ret;
-
-	if (poll_on) {
-		blk_queue_flag_set(QUEUE_FLAG_POLL, q);
-	} else {
-		blk_mq_freeze_queue(q);
-		blk_queue_flag_clear(QUEUE_FLAG_POLL, q);
-		blk_mq_unfreeze_queue(q);
-	}
-
-	return ret;
+	pr_info_ratelimited("writes to the poll attribute are ignored.\n");
+	pr_info_ratelimited("please use driver specific parameters instead.\n");
+	return count;
 }
 
 static ssize_t queue_io_timeout_show(struct request_queue *q, char *page)