Commit 28d949bc authored by Bob Liu's avatar Bob Liu Committed by Konrad Rzeszutek Wilk
Browse files

xen/blkfront: negotiate number of queues/rings to be used with backend 



The max number of hardware queues for xen/blkfront is set by parameter
'max_queues'(default 4), while it is also capped by the max value that the
xen/blkback exposes through XenStore key 'multi-queue-max-queues'.

The negotiated number is the smaller one and would be written back to xenstore
as "multi-queue-num-queues", blkback needs to read this negotiated number.

Signed-off-by: default avatarBob Liu <bob.liu@oracle.com>
Signed-off-by: default avatarKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>
parent 11659569

drivers/block/xen-blkfront.c

+119 −41
Original line number Diff line number Diff line
@@ -99,6 +99,10 @@ static unsigned int xen_blkif_max_segments = 32; 
module_param_named(max, xen_blkif_max_segments, int, S_IRUGO);

MODULE_PARM_DESC(max, "Maximum amount of segments in indirect requests (default is 32)");



static unsigned int xen_blkif_max_queues = 4;

module_param_named(max_queues, xen_blkif_max_queues, uint, S_IRUGO);

MODULE_PARM_DESC(max_queues, "Maximum number of hardware queues/rings used per virtual disk");



/*

 * Maximum order of pages to be used for the shared ring between front and

 * backend, 4KB page granularity is used.
@@ -118,6 +122,10 @@ MODULE_PARM_DESC(max_ring_page_order, "Maximum order of pages to be used for the 
 * characters are enough. Define to 20 to keep consist with backend.

 */

#define RINGREF_NAME_LEN (20)

/*

 * queue-%u would take 7 + 10(UINT_MAX) = 17 characters.

 */

#define QUEUE_NAME_LEN (17)



/*

 *  Per-ring info.
@@ -823,7 +831,7 @@ static int xlvbd_init_blk_queue(struct gendisk *gd, u16 sector_size, 


	memset(&info->tag_set, 0, sizeof(info->tag_set));

	info->tag_set.ops = &blkfront_mq_ops;

	info->tag_set.nr_hw_queues = 1;

	info->tag_set.nr_hw_queues = info->nr_rings;

	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 | BLK_MQ_F_SG_MERGE;
@@ -1522,6 +1530,53 @@ fail: 
	return err;

}



/*

 * Write out per-ring/queue nodes including ring-ref and event-channel, and each

 * ring buffer may have multi pages depending on ->nr_ring_pages.

 */

static int write_per_ring_nodes(struct xenbus_transaction xbt,

				struct blkfront_ring_info *rinfo, const char *dir)

{

	int err;

	unsigned int i;

	const char *message = NULL;

	struct blkfront_info *info = rinfo->dev_info;



	if (info->nr_ring_pages == 1) {

		err = xenbus_printf(xbt, dir, "ring-ref", "%u", rinfo->ring_ref[0]);

		if (err) {

			message = "writing ring-ref";

			goto abort_transaction;

		}

	} else {

		for (i = 0; i < info->nr_ring_pages; i++) {

			char ring_ref_name[RINGREF_NAME_LEN];



			snprintf(ring_ref_name, RINGREF_NAME_LEN, "ring-ref%u", i);

			err = xenbus_printf(xbt, dir, ring_ref_name,

					    "%u", rinfo->ring_ref[i]);

			if (err) {

				message = "writing ring-ref";

				goto abort_transaction;

			}

		}

	}



	err = xenbus_printf(xbt, dir, "event-channel", "%u", rinfo->evtchn);

	if (err) {

		message = "writing event-channel";

		goto abort_transaction;

	}



	return 0;



abort_transaction:

	xenbus_transaction_end(xbt, 1);

	if (message)

		xenbus_dev_fatal(info->xbdev, err, "%s", message);



	return err;

}



/* Common code used when first setting up, and when resuming. */

static int talk_to_blkback(struct xenbus_device *dev,
@@ -1529,10 +1584,9 @@ static int talk_to_blkback(struct xenbus_device *dev, 
{

	const char *message = NULL;

	struct xenbus_transaction xbt;

	int err, i;

	unsigned int max_page_order = 0;

	int err;

	unsigned int i, max_page_order = 0;

	unsigned int ring_page_order = 0;

	struct blkfront_ring_info *rinfo;



	err = xenbus_scanf(XBT_NIL, info->xbdev->otherend,

			   "max-ring-page-order", "%u", &max_page_order);
@@ -1544,7 +1598,8 @@ static int talk_to_blkback(struct xenbus_device *dev, 
	}



	for (i = 0; i < info->nr_rings; i++) {

		rinfo = &info->rinfo[i];

		struct blkfront_ring_info *rinfo = &info->rinfo[i];



		/* Create shared ring, alloc event channel. */

		err = setup_blkring(dev, rinfo);

		if (err)
@@ -1558,44 +1613,49 @@ again: 
		goto destroy_blkring;

	}



	if (info->nr_rings == 1) {

		rinfo = &info->rinfo[0];

		if (info->nr_ring_pages == 1) {

			err = xenbus_printf(xbt, dev->nodename,

					    "ring-ref", "%u", rinfo->ring_ref[0]);

			if (err) {

				message = "writing ring-ref";

				goto abort_transaction;

			}

		} else {

			err = xenbus_printf(xbt, dev->nodename,

					    "ring-page-order", "%u", ring_page_order);

	if (info->nr_ring_pages > 1) {

		err = xenbus_printf(xbt, dev->nodename, "ring-page-order", "%u",

				    ring_page_order);

		if (err) {

			message = "writing ring-page-order";

			goto abort_transaction;

		}

	}



			for (i = 0; i < info->nr_ring_pages; i++) {

				char ring_ref_name[RINGREF_NAME_LEN];

	/* We already got the number of queues/rings in _probe */

	if (info->nr_rings == 1) {

		err = write_per_ring_nodes(xbt, &info->rinfo[0], dev->nodename);

		if (err)

			goto destroy_blkring;

	} else {

		char *path;

		size_t pathsize;



				snprintf(ring_ref_name, RINGREF_NAME_LEN, "ring-ref%u", i);

				err = xenbus_printf(xbt, dev->nodename, ring_ref_name,

						    "%u", rinfo->ring_ref[i]);

		err = xenbus_printf(xbt, dev->nodename, "multi-queue-num-queues", "%u",

				    info->nr_rings);

		if (err) {

					message = "writing ring-ref";

			message = "writing multi-queue-num-queues";

			goto abort_transaction;

		}



		pathsize = strlen(dev->nodename) + QUEUE_NAME_LEN;

		path = kmalloc(pathsize, GFP_KERNEL);

		if (!path) {

			err = -ENOMEM;

			message = "ENOMEM while writing ring references";

			goto abort_transaction;

		}

		}

		err = xenbus_printf(xbt, dev->nodename,

				    "event-channel", "%u", rinfo->evtchn);



		for (i = 0; i < info->nr_rings; i++) {

			memset(path, 0, pathsize);

			snprintf(path, pathsize, "%s/queue-%u", dev->nodename, i);

			err = write_per_ring_nodes(xbt, &info->rinfo[i], path);

			if (err) {

			message = "writing event-channel";

			goto abort_transaction;

				kfree(path);

				goto destroy_blkring;

			}

	} else {

		/* Not supported at this stage. */

		goto abort_transaction;

		}

		kfree(path);

	}

	err = xenbus_printf(xbt, dev->nodename, "protocol", "%s",

			    XEN_IO_PROTO_ABI_NATIVE);
@@ -1619,8 +1679,7 @@ again: 


	for (i = 0; i < info->nr_rings; i++) {

		unsigned int j;



		rinfo = &info->rinfo[i];

		struct blkfront_ring_info *rinfo = &info->rinfo[i];



		for (j = 0; j < BLK_RING_SIZE(info); j++)

			rinfo->shadow[j].req.u.rw.id = j + 1;
@@ -1652,6 +1711,7 @@ static int blkfront_probe(struct xenbus_device *dev, 
	int err, vdevice;

	unsigned int r_index;

	struct blkfront_info *info;

	unsigned int backend_max_queues = 0;



	/* FIXME: Use dynamic device id if this is not set. */

	err = xenbus_scanf(XBT_NIL, dev->nodename,
@@ -1701,7 +1761,18 @@ static int blkfront_probe(struct xenbus_device *dev, 
		return -ENOMEM;

	}



	info->xbdev = dev;

	/* Check if backend supports multiple queues. */

	err = xenbus_scanf(XBT_NIL, info->xbdev->otherend,

			   "multi-queue-max-queues", "%u", &backend_max_queues);

	if (err < 0)

		backend_max_queues = 1;



	info->nr_rings = min(backend_max_queues, xen_blkif_max_queues);

	/* We need at least one ring. */

	if (!info->nr_rings)

		info->nr_rings = 1;



	info->rinfo = kzalloc(sizeof(struct blkfront_ring_info) * info->nr_rings, GFP_KERNEL);

	if (!info->rinfo) {

		xenbus_dev_fatal(dev, -ENOMEM, "allocating ring_info structure");
@@ -2390,6 +2461,7 @@ static struct xenbus_driver blkfront_driver = { 
static int __init xlblk_init(void)

{

	int ret;

	int nr_cpus = num_online_cpus();



	if (!xen_domain())

		return -ENODEV;
@@ -2400,6 +2472,12 @@ static int __init xlblk_init(void) 
		xen_blkif_max_ring_order = 0;

	}



	if (xen_blkif_max_queues > nr_cpus) {

		pr_info("Invalid max_queues (%d), will use default max: %d.\n",

			xen_blkif_max_queues, nr_cpus);

		xen_blkif_max_queues = nr_cpus;

	}



	if (!xen_has_pv_disk_devices())

		return -ENODEV;

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