block: remove BLK_MQ_F_SHOULD_MERGE

BLK_MQ_F_SHOULD_MERGE is set for all tag_sets except those that purely
process passthrough commands (bsg-lib, ufs tmf, various nvme admin
queues) and thus don't even check the flag. Remove it to simplify the
driver interface.

Signed-off-by: Christoph Hellwig <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Jens Axboe <[e-mail]>

arch/um/drivers/ubd_kern.c

···
 	ubd_dev->tag_set.ops = &ubd_mq_ops;
 	ubd_dev->tag_set.queue_depth = 64;
 	ubd_dev->tag_set.numa_node = NUMA_NO_NODE;
-	ubd_dev->tag_set.flags = BLK_MQ_F_SHOULD_MERGE;
 	ubd_dev->tag_set.driver_data = ubd_dev;
 	ubd_dev->tag_set.nr_hw_queues = 1;
 

block/blk-mq-debugfs.c

···
 
 #define HCTX_FLAG_NAME(name) [ilog2(BLK_MQ_F_##name)] = #name
 static const char *const hctx_flag_name[] = {
-	HCTX_FLAG_NAME(SHOULD_MERGE),
 	HCTX_FLAG_NAME(TAG_QUEUE_SHARED),
 	HCTX_FLAG_NAME(STACKING),
 	HCTX_FLAG_NAME(TAG_HCTX_SHARED),

block/blk-mq-sched.c

···
 	ctx = blk_mq_get_ctx(q);
 	hctx = blk_mq_map_queue(q, bio->bi_opf, ctx);
 	type = hctx->type;
-	if (!(hctx->flags & BLK_MQ_F_SHOULD_MERGE) ||
-	    list_empty_careful(&ctx->rq_lists[type]))
+	if (list_empty_careful(&ctx->rq_lists[type]))
 		goto out_put;
 
 	/* default per sw-queue merge */

drivers/block/amiflop.c

···
 	unit[drive].tag_set.nr_maps = 1;
 	unit[drive].tag_set.queue_depth = 2;
 	unit[drive].tag_set.numa_node = NUMA_NO_NODE;
-	unit[drive].tag_set.flags = BLK_MQ_F_SHOULD_MERGE;
 	if (blk_mq_alloc_tag_set(&unit[drive].tag_set))
 		goto out_cleanup_trackbuf;
 

drivers/block/aoe/aoeblk.c

···
 	set->nr_hw_queues = 1;
 	set->queue_depth = 128;
 	set->numa_node = NUMA_NO_NODE;
-	set->flags = BLK_MQ_F_SHOULD_MERGE;
 	err = blk_mq_alloc_tag_set(set);
 	if (err) {
 		pr_err("aoe: cannot allocate tag set for %ld.%d\n",

drivers/block/ataflop.c

···
 		unit[i].tag_set.nr_maps = 1;
 		unit[i].tag_set.queue_depth = 2;
 		unit[i].tag_set.numa_node = NUMA_NO_NODE;
-		unit[i].tag_set.flags = BLK_MQ_F_SHOULD_MERGE;
 		ret = blk_mq_alloc_tag_set(&unit[i].tag_set);
 		if (ret)
 			goto err;

drivers/block/floppy.c

···
 		tag_sets[drive].nr_maps = 1;
 		tag_sets[drive].queue_depth = 2;
 		tag_sets[drive].numa_node = NUMA_NO_NODE;
-		tag_sets[drive].flags = BLK_MQ_F_SHOULD_MERGE;
 		err = blk_mq_alloc_tag_set(&tag_sets[drive]);
 		if (err)
 			goto out_put_disk;

drivers/block/loop.c

···
 	lo->tag_set.queue_depth = hw_queue_depth;
 	lo->tag_set.numa_node = NUMA_NO_NODE;
 	lo->tag_set.cmd_size = sizeof(struct loop_cmd);
-	lo->tag_set.flags = BLK_MQ_F_SHOULD_MERGE | BLK_MQ_F_STACKING |
-		BLK_MQ_F_NO_SCHED_BY_DEFAULT;
+	lo->tag_set.flags = BLK_MQ_F_STACKING | BLK_MQ_F_NO_SCHED_BY_DEFAULT;
 	lo->tag_set.driver_data = lo;
 
 	err = blk_mq_alloc_tag_set(&lo->tag_set);

drivers/block/mtip32xx/mtip32xx.c

···
 	dd->tags.reserved_tags = 1;
 	dd->tags.cmd_size = sizeof(struct mtip_cmd);
 	dd->tags.numa_node = dd->numa_node;
-	dd->tags.flags = BLK_MQ_F_SHOULD_MERGE;
 	dd->tags.driver_data = dd;
 	dd->tags.timeout = MTIP_NCQ_CMD_TIMEOUT_MS;
 

drivers/block/nbd.c

···
 	nbd->tag_set.queue_depth = 128;
 	nbd->tag_set.numa_node = NUMA_NO_NODE;
 	nbd->tag_set.cmd_size = sizeof(struct nbd_cmd);
-	nbd->tag_set.flags = BLK_MQ_F_SHOULD_MERGE |
-		BLK_MQ_F_BLOCKING;
+	nbd->tag_set.flags = BLK_MQ_F_BLOCKING;
 	nbd->tag_set.driver_data = nbd;
 	INIT_WORK(&nbd->remove_work, nbd_dev_remove_work);
 	nbd->backend = NULL;

drivers/block/null_blk/main.c

···
 	tag_set.nr_hw_queues = g_submit_queues;
 	tag_set.queue_depth = g_hw_queue_depth;
 	tag_set.numa_node = g_home_node;
-	tag_set.flags = BLK_MQ_F_SHOULD_MERGE;
 	if (g_no_sched)
 		tag_set.flags |= BLK_MQ_F_NO_SCHED;
 	if (g_shared_tag_bitmap)
···
 	nullb->tag_set->nr_hw_queues = nullb->dev->submit_queues;
 	nullb->tag_set->queue_depth = nullb->dev->hw_queue_depth;
 	nullb->tag_set->numa_node = nullb->dev->home_node;
-	nullb->tag_set->flags = BLK_MQ_F_SHOULD_MERGE;
 	if (nullb->dev->no_sched)
 		nullb->tag_set->flags |= BLK_MQ_F_NO_SCHED;
 	if (nullb->dev->shared_tag_bitmap)

drivers/block/ps3disk.c

···
 
 	ps3disk_identify(dev);
 
-	error = blk_mq_alloc_sq_tag_set(&priv->tag_set, &ps3disk_mq_ops, 1,
-					BLK_MQ_F_SHOULD_MERGE);
+	error = blk_mq_alloc_sq_tag_set(&priv->tag_set, &ps3disk_mq_ops, 1, 0);
 	if (error)
 		goto fail_teardown;
 

drivers/block/rbd.c

···
 	rbd_dev->tag_set.ops = &rbd_mq_ops;
 	rbd_dev->tag_set.queue_depth = rbd_dev->opts->queue_depth;
 	rbd_dev->tag_set.numa_node = NUMA_NO_NODE;
-	rbd_dev->tag_set.flags = BLK_MQ_F_SHOULD_MERGE;
 	rbd_dev->tag_set.nr_hw_queues = num_present_cpus();
 	rbd_dev->tag_set.cmd_size = sizeof(struct rbd_img_request);
 

drivers/block/rnbd/rnbd-clt.c

···
 	tag_set->ops		= &rnbd_mq_ops;
 	tag_set->queue_depth	= sess->queue_depth;
 	tag_set->numa_node		= NUMA_NO_NODE;
-	tag_set->flags		= BLK_MQ_F_SHOULD_MERGE |
-				  BLK_MQ_F_TAG_QUEUE_SHARED;
+	tag_set->flags		= BLK_MQ_F_TAG_QUEUE_SHARED;
 	tag_set->cmd_size	= sizeof(struct rnbd_iu) + RNBD_RDMA_SGL_SIZE;
 
 	/* for HCTX_TYPE_DEFAULT, HCTX_TYPE_READ, HCTX_TYPE_POLL */

drivers/block/sunvdc.c

···
 	}
 
 	err = blk_mq_alloc_sq_tag_set(&port->tag_set, &vdc_mq_ops,
-			VDC_TX_RING_SIZE, BLK_MQ_F_SHOULD_MERGE);
+			VDC_TX_RING_SIZE, 0);
 	if (err)
 		return err;
 

drivers/block/swim.c

···
 
 	for (drive = 0; drive < swd->floppy_count; drive++) {
 		err = blk_mq_alloc_sq_tag_set(&swd->unit[drive].tag_set,
-				&swim_mq_ops, 2, BLK_MQ_F_SHOULD_MERGE);
+				&swim_mq_ops, 2, 0);
 		if (err)
 			goto exit_put_disks;
 

drivers/block/swim3.c

···
 	fs = &floppy_states[floppy_count];
 	memset(fs, 0, sizeof(*fs));
 
-	rc = blk_mq_alloc_sq_tag_set(&fs->tag_set, &swim3_mq_ops, 2,
-			BLK_MQ_F_SHOULD_MERGE);
+	rc = blk_mq_alloc_sq_tag_set(&fs->tag_set, &swim3_mq_ops, 2, 0);
 	if (rc)
 		goto out_unregister;
 

drivers/block/ublk_drv.c

···
 	ub->tag_set.queue_depth = ub->dev_info.queue_depth;
 	ub->tag_set.numa_node = NUMA_NO_NODE;
 	ub->tag_set.cmd_size = sizeof(struct ublk_rq_data);
-	ub->tag_set.flags = BLK_MQ_F_SHOULD_MERGE;
 	ub->tag_set.driver_data = ub;
 	return blk_mq_alloc_tag_set(&ub->tag_set);
 }

drivers/block/virtio_blk.c

···
 	vblk->tag_set.ops = &virtio_mq_ops;
 	vblk->tag_set.queue_depth = queue_depth;
 	vblk->tag_set.numa_node = NUMA_NO_NODE;
-	vblk->tag_set.flags = BLK_MQ_F_SHOULD_MERGE;
 	vblk->tag_set.cmd_size =
 		sizeof(struct virtblk_req) +
 		sizeof(struct scatterlist) * VIRTIO_BLK_INLINE_SG_CNT;

drivers/block/xen-blkfront.c

···
 	} else
 		info->tag_set.queue_depth = BLK_RING_SIZE(info);
 	info->tag_set.numa_node = NUMA_NO_NODE;
-	info->tag_set.flags = BLK_MQ_F_SHOULD_MERGE;
 	info->tag_set.cmd_size = sizeof(struct blkif_req);
 	info->tag_set.driver_data = info;
 

drivers/block/z2ram.c

···
 	tag_set.nr_maps = 1;
 	tag_set.queue_depth = 16;
 	tag_set.numa_node = NUMA_NO_NODE;
-	tag_set.flags = BLK_MQ_F_SHOULD_MERGE;
 	ret = blk_mq_alloc_tag_set(&tag_set);
 	if (ret)
 		goto out_unregister_blkdev;

drivers/cdrom/gdrom.c

···
 	probe_gdrom_setupcd();
 
 	err = blk_mq_alloc_sq_tag_set(&gd.tag_set, &gdrom_mq_ops, 1,
-				BLK_MQ_F_SHOULD_MERGE | BLK_MQ_F_BLOCKING);
+				BLK_MQ_F_BLOCKING);
 	if (err)
 		goto probe_fail_free_cd_info;
 

drivers/md/dm-rq.c

···
 	md->tag_set->ops = &dm_mq_ops;
 	md->tag_set->queue_depth = dm_get_blk_mq_queue_depth();
 	md->tag_set->numa_node = md->numa_node_id;
-	md->tag_set->flags = BLK_MQ_F_SHOULD_MERGE | BLK_MQ_F_STACKING;
+	md->tag_set->flags = BLK_MQ_F_STACKING;
 	md->tag_set->nr_hw_queues = dm_get_blk_mq_nr_hw_queues();
 	md->tag_set->driver_data = md;
 

drivers/memstick/core/ms_block.c

···
 	if (msb->disk_id  < 0)
 		return msb->disk_id;
 
-	rc = blk_mq_alloc_sq_tag_set(&msb->tag_set, &msb_mq_ops, 2,
-				     BLK_MQ_F_SHOULD_MERGE);
+	rc = blk_mq_alloc_sq_tag_set(&msb->tag_set, &msb_mq_ops, 2, 0);
 	if (rc)
 		goto out_release_id;
 

drivers/memstick/core/mspro_block.c

···
 	if (disk_id < 0)
 		return disk_id;
 
-	rc = blk_mq_alloc_sq_tag_set(&msb->tag_set, &mspro_mq_ops, 2,
-				     BLK_MQ_F_SHOULD_MERGE);
+	rc = blk_mq_alloc_sq_tag_set(&msb->tag_set, &mspro_mq_ops, 2, 0);
 	if (rc)
 		goto out_release_id;
 

drivers/mmc/core/queue.c

···
 	else
 		mq->tag_set.queue_depth = MMC_QUEUE_DEPTH;
 	mq->tag_set.numa_node = NUMA_NO_NODE;
-	mq->tag_set.flags = BLK_MQ_F_SHOULD_MERGE | BLK_MQ_F_BLOCKING;
+	mq->tag_set.flags = BLK_MQ_F_BLOCKING;
 	mq->tag_set.nr_hw_queues = 1;
 	mq->tag_set.cmd_size = sizeof(struct mmc_queue_req);
 	mq->tag_set.driver_data = mq;

drivers/mtd/mtd_blkdevs.c

···
 		goto out_list_del;
 
 	ret = blk_mq_alloc_sq_tag_set(new->tag_set, &mtd_mq_ops, 2,
-			BLK_MQ_F_SHOULD_MERGE | BLK_MQ_F_BLOCKING);
+			BLK_MQ_F_BLOCKING);
 	if (ret)
 		goto out_kfree_tag_set;
 	

drivers/mtd/ubi/block.c

···
 	dev->tag_set.ops = &ubiblock_mq_ops;
 	dev->tag_set.queue_depth = 64;
 	dev->tag_set.numa_node = NUMA_NO_NODE;
-	dev->tag_set.flags = BLK_MQ_F_SHOULD_MERGE | BLK_MQ_F_BLOCKING;
+	dev->tag_set.flags = BLK_MQ_F_BLOCKING;
 	dev->tag_set.cmd_size = sizeof(struct ubiblock_pdu);
 	dev->tag_set.driver_data = dev;
 	dev->tag_set.nr_hw_queues = 1;

drivers/nvme/host/apple.c

···
 	anv->tagset.timeout = NVME_IO_TIMEOUT;
 	anv->tagset.numa_node = NUMA_NO_NODE;
 	anv->tagset.cmd_size = sizeof(struct apple_nvme_iod);
-	anv->tagset.flags = BLK_MQ_F_SHOULD_MERGE;
 	anv->tagset.driver_data = &anv->ioq;
 
 	ret = blk_mq_alloc_tag_set(&anv->tagset);

drivers/nvme/host/core.c

···
 		/* Reserved for fabric connect */
 		set->reserved_tags = 1;
 	set->numa_node = ctrl->numa_node;
-	set->flags = BLK_MQ_F_SHOULD_MERGE;
 	if (ctrl->ops->flags & NVME_F_BLOCKING)
 		set->flags |= BLK_MQ_F_BLOCKING;
 	set->cmd_size = cmd_size;

drivers/s390/block/dasd_genhd.c

···
 	block->tag_set.cmd_size = sizeof(struct dasd_ccw_req);
 	block->tag_set.nr_hw_queues = nr_hw_queues;
 	block->tag_set.queue_depth = queue_depth;
-	block->tag_set.flags = BLK_MQ_F_SHOULD_MERGE;
 	block->tag_set.numa_node = NUMA_NO_NODE;
 	rc = blk_mq_alloc_tag_set(&block->tag_set);
 	if (rc)

drivers/s390/block/scm_blk.c

···
 	bdev->tag_set.cmd_size = sizeof(blk_status_t);
 	bdev->tag_set.nr_hw_queues = nr_requests;
 	bdev->tag_set.queue_depth = nr_requests_per_io * nr_requests;
-	bdev->tag_set.flags = BLK_MQ_F_SHOULD_MERGE;
 	bdev->tag_set.numa_node = NUMA_NO_NODE;
 
 	ret = blk_mq_alloc_tag_set(&bdev->tag_set);

drivers/scsi/scsi_lib.c

···
 	tag_set->queue_depth = shost->can_queue;
 	tag_set->cmd_size = cmd_size;
 	tag_set->numa_node = dev_to_node(shost->dma_dev);
-	tag_set->flags = BLK_MQ_F_SHOULD_MERGE;
 	tag_set->flags |=
 		BLK_ALLOC_POLICY_TO_MQ_FLAG(shost->hostt->tag_alloc_policy);
 	if (shost->queuecommand_may_block)

include/linux/blk-mq.h

···
 
 /* Keep hctx_flag_name[] in sync with the definitions below */
 enum {
-	BLK_MQ_F_SHOULD_MERGE	= 1 << 0,
 	BLK_MQ_F_TAG_QUEUE_SHARED = 1 << 1,
 	/*
 	 * Set when this device requires underlying blk-mq device for