[PATCH v4 07/10] xen/blkback: pseudo support for multi hardware queues/rings

From: Bob Liu <bob.liu@oracle.com>
To: xen-devel@lists.xen.org
Cc: linux-kernel@vger.kernel.org, roger.pau@citrix.com,
	konrad.wilk@oracle.com, felipe.franciosi@citrix.com,
	axboe@fb.com, avanzini.arianna@gmail.com,
	rafal.mielniczuk@citrix.com, jonathan.davies@citrix.com,
	david.vrabel@citrix.com, Bob Liu <bob.liu@oracle.com>
Subject: [PATCH v4 07/10] xen/blkback: pseudo support for multi hardware queues/rings
Date: Mon,  2 Nov 2015 12:21:43 +0800	[thread overview]
Message-ID: <1446438106-20171-8-git-send-email-bob.liu@oracle.com> (raw)
In-Reply-To: <1446438106-20171-1-git-send-email-bob.liu@oracle.com>

Preparatory patch for multiple hardware queues (rings). The number of
rings is unconditionally set to 1, larger number will be enabled in next
patch so as to make every single patch small and readable.

Signed-off-by: Arianna Avanzini <avanzini.arianna@gmail.com>
Signed-off-by: Bob Liu <bob.liu@oracle.com>
---
 drivers/block/xen-blkback/common.h |   3 +-
 drivers/block/xen-blkback/xenbus.c | 292 +++++++++++++++++++++++--------------
 2 files changed, 185 insertions(+), 110 deletions(-)

diff --git a/drivers/block/xen-blkback/common.h b/drivers/block/xen-blkback/common.h
index f0dd69a..4de1326 100644
--- a/drivers/block/xen-blkback/common.h
+++ b/drivers/block/xen-blkback/common.h
@@ -341,7 +341,8 @@ struct xen_blkif {
 	struct work_struct	free_work;
 	unsigned int nr_ring_pages;
 	/* All rings for this device */
-	struct xen_blkif_ring ring;
+	struct xen_blkif_ring *rings;
+	unsigned int nr_rings;
 };
 
 struct seg_buf {
diff --git a/drivers/block/xen-blkback/xenbus.c b/drivers/block/xen-blkback/xenbus.c
index 7bdd5fd..ac4b458 100644
--- a/drivers/block/xen-blkback/xenbus.c
+++ b/drivers/block/xen-blkback/xenbus.c
@@ -84,11 +84,12 @@ static int blkback_name(struct xen_blkif *blkif, char *buf)
 
 static void xen_update_blkif_status(struct xen_blkif *blkif)
 {
-	int err;
+	int err, i;
 	char name[BLKBACK_NAME_LEN];
+	struct xen_blkif_ring *ring;
 
 	/* Not ready to connect? */
-	if (!blkif->ring.irq || !blkif->vbd.bdev)
+	if (!blkif->rings || !blkif->rings[0].irq || !blkif->vbd.bdev)
 		return;
 
 	/* Already connected? */
@@ -113,19 +114,57 @@ static void xen_update_blkif_status(struct xen_blkif *blkif)
 	}
 	invalidate_inode_pages2(blkif->vbd.bdev->bd_inode->i_mapping);
 
-	blkif->ring.xenblkd = kthread_run(xen_blkif_schedule, &blkif->ring, "%s", name);
-	if (IS_ERR(blkif->ring.xenblkd)) {
-		err = PTR_ERR(blkif->ring.xenblkd);
-		blkif->ring.xenblkd = NULL;
-		xenbus_dev_error(blkif->be->dev, err, "start xenblkd");
-		return;
+	if (blkif->nr_rings == 1) {
+		blkif->rings[0].xenblkd = kthread_run(xen_blkif_schedule, &blkif->rings[0], "%s", name);
+		if (IS_ERR(blkif->rings[0].xenblkd)) {
+			err = PTR_ERR(blkif->rings[0].xenblkd);
+			blkif->rings[0].xenblkd = NULL;
+			xenbus_dev_error(blkif->be->dev, err, "start xenblkd");
+			return;
+		}
+	} else {
+		for (i = 0; i < blkif->nr_rings; i++) {
+			ring = &blkif->rings[i];
+			ring->xenblkd = kthread_run(xen_blkif_schedule, ring, "%s-%d", name, i);
+			if (IS_ERR(ring->xenblkd)) {
+				err = PTR_ERR(ring->xenblkd);
+				ring->xenblkd = NULL;
+				xenbus_dev_error(blkif->be->dev, err,
+						"start %s-%d xenblkd", name, i);
+				return;
+			}
+		}
+	}
+}
+
+static int xen_blkif_alloc_rings(struct xen_blkif *blkif)
+{
+	int r;
+
+	blkif->rings = kzalloc(blkif->nr_rings * sizeof(struct xen_blkif_ring), GFP_KERNEL);
+	if (!blkif->rings)
+		return -ENOMEM;
+
+	for (r = 0; r < blkif->nr_rings; r++) {
+		struct xen_blkif_ring *ring = &blkif->rings[r];
+
+		spin_lock_init(&ring->blk_ring_lock);
+		init_waitqueue_head(&ring->wq);
+		INIT_LIST_HEAD(&ring->pending_free);
+
+		spin_lock_init(&ring->pending_free_lock);
+		init_waitqueue_head(&ring->pending_free_wq);
+		init_waitqueue_head(&ring->shutdown_wq);
+		ring->blkif = blkif;
+		xen_blkif_get(blkif);
 	}
+
+	return 0;
 }
 
 static struct xen_blkif *xen_blkif_alloc(domid_t domid)
 {
 	struct xen_blkif *blkif;
-	struct xen_blkif_ring *ring;
 
 	BUILD_BUG_ON(MAX_INDIRECT_PAGES > BLKIF_MAX_INDIRECT_PAGES_PER_REQUEST);
 
@@ -136,27 +175,17 @@ static struct xen_blkif *xen_blkif_alloc(domid_t domid)
 	blkif->domid = domid;
 	atomic_set(&blkif->refcnt, 1);
 	init_completion(&blkif->drain_complete);
-	atomic_set(&blkif->drain, 0);
 	INIT_WORK(&blkif->free_work, xen_blkif_deferred_free);
 	spin_lock_init(&blkif->free_pages_lock);
 	INIT_LIST_HEAD(&blkif->free_pages);
-	blkif->free_pages_num = 0;
-	blkif->persistent_gnts.rb_node = NULL;
 	INIT_LIST_HEAD(&blkif->persistent_purge_list);
-	atomic_set(&blkif->persistent_gnt_in_use, 0);
 	INIT_WORK(&blkif->persistent_purge_work, xen_blkbk_unmap_purged_grants);
 
-	ring = &blkif->ring;
-	ring->blkif = blkif;
-	spin_lock_init(&ring->blk_ring_lock);
-	init_waitqueue_head(&ring->wq);
-	ring->st_print = jiffies;
-	atomic_set(&ring->inflight, 0);
-
-	INIT_LIST_HEAD(&ring->pending_free);
-	spin_lock_init(&ring->pending_free_lock);
-	init_waitqueue_head(&ring->pending_free_wq);
-	init_waitqueue_head(&ring->shutdown_wq);
+	blkif->nr_rings = 1;
+	if (xen_blkif_alloc_rings(blkif)) {
+		kmem_cache_free(xen_blkif_cachep, blkif);
+		return ERR_PTR(-ENOMEM);
+	}
 
 	return blkif;
 }
@@ -218,50 +247,54 @@ static int xen_blkif_map(struct xen_blkif_ring *ring, grant_ref_t *gref,
 static int xen_blkif_disconnect(struct xen_blkif *blkif)
 {
 	struct pending_req *req, *n;
-	int i = 0, j;
-	struct xen_blkif_ring *ring = &blkif->ring;
+	int j, r;
 
-	if (ring->xenblkd) {
-		kthread_stop(ring->xenblkd);
-		wake_up(&ring->shutdown_wq);
-		ring->xenblkd = NULL;
-	}
+	for (r = 0; r < blkif->nr_rings; r++) {
+		struct xen_blkif_ring *ring = &blkif->rings[r];
+		int i = 0;
 
-	/* The above kthread_stop() guarantees that at this point we
-	 * don't have any discard_io or other_io requests. So, checking
-	 * for inflight IO is enough.
-	 */
-	if (atomic_read(&ring->inflight) > 0)
-		return -EBUSY;
+		if (ring->xenblkd) {
+			kthread_stop(ring->xenblkd);
+			wake_up(&ring->shutdown_wq);
+			ring->xenblkd = NULL;
+		}
 
-	if (ring->irq) {
-		unbind_from_irqhandler(ring->irq, ring);
-		ring->irq = 0;
-	}
+		/* The above kthread_stop() guarantees that at this point we
+		 * don't have any discard_io or other_io requests. So, checking
+		 * for inflight IO is enough.
+		 */
+		if (atomic_read(&ring->inflight) > 0)
+			return -EBUSY;
 
-	if (ring->blk_rings.common.sring) {
-		xenbus_unmap_ring_vfree(blkif->be->dev, ring->blk_ring);
-		ring->blk_rings.common.sring = NULL;
-	}
+		if (ring->irq) {
+			unbind_from_irqhandler(ring->irq, ring);
+			ring->irq = 0;
+		}
 
-	/* Remove all persistent grants and the cache of ballooned pages. */
-	xen_blkbk_free_caches(ring);
+		if (ring->blk_rings.common.sring) {
+			xenbus_unmap_ring_vfree(blkif->be->dev, ring->blk_ring);
+			ring->blk_rings.common.sring = NULL;
+		}
 
-	/* Check that there is no request in use */
-	list_for_each_entry_safe(req, n, &ring->pending_free, free_list) {
-		list_del(&req->free_list);
+		/* Remove all persistent grants and the cache of ballooned pages. */
+		xen_blkbk_free_caches(ring);
 
-		for (j = 0; j < MAX_INDIRECT_SEGMENTS; j++)
-			kfree(req->segments[j]);
+		/* Check that there is no request in use */
+		list_for_each_entry_safe(req, n, &ring->pending_free, free_list) {
+			list_del(&req->free_list);
 
-		for (j = 0; j < MAX_INDIRECT_PAGES; j++)
-			kfree(req->indirect_pages[j]);
+			for (j = 0; j < MAX_INDIRECT_SEGMENTS; j++)
+				kfree(req->segments[j]);
 
-		kfree(req);
-		i++;
-	}
+			for (j = 0; j < MAX_INDIRECT_PAGES; j++)
+				kfree(req->indirect_pages[j]);
 
-	WARN_ON(i != (XEN_BLKIF_REQS_PER_PAGE * blkif->nr_ring_pages));
+			kfree(req);
+			i++;
+		}
+
+		WARN_ON(i != (XEN_BLKIF_REQS_PER_PAGE * blkif->nr_ring_pages));
+	}
 	blkif->nr_ring_pages = 0;
 
 	return 0;
@@ -281,6 +314,7 @@ static void xen_blkif_free(struct xen_blkif *blkif)
 	BUG_ON(!list_empty(&blkif->free_pages));
 	BUG_ON(!RB_EMPTY_ROOT(&blkif->persistent_gnts));
 
+	kfree(blkif->rings);
 	kmem_cache_free(xen_blkif_cachep, blkif);
 }
 
@@ -307,15 +341,19 @@ int __init xen_blkif_interface_init(void)
 		struct xenbus_device *dev = to_xenbus_device(_dev);	\
 		struct backend_info *be = dev_get_drvdata(&dev->dev);	\
 		struct xen_blkif *blkif = be->blkif;			\
-		struct xen_blkif_ring *ring = &blkif->ring;		\
+		int i;							\
+									\
+		for (i = 0; i < blkif->nr_rings; i++) {			\
+			struct xen_blkif_ring *ring = &blkif->rings[i];	\
 									\
-		blkif->st_oo_req = ring->st_oo_req;			\
-		blkif->st_rd_req = ring->st_rd_req;			\
-		blkif->st_wr_req = ring->st_wr_req;			\
-		blkif->st_f_req = ring->st_f_req;			\
-		blkif->st_ds_req = ring->st_ds_req;			\
-		blkif->st_rd_sect = ring->st_rd_sect;			\
-		blkif->st_wr_sect = ring->st_wr_sect;			\
+			blkif->st_oo_req += ring->st_oo_req;		\
+			blkif->st_rd_req += ring->st_rd_req;		\
+			blkif->st_wr_req += ring->st_wr_req;		\
+			blkif->st_f_req += ring->st_f_req;		\
+			blkif->st_ds_req += ring->st_ds_req;		\
+			blkif->st_rd_sect += ring->st_rd_sect;		\
+			blkif->st_wr_sect += ring->st_wr_sect;		\
+		}							\
 									\
 		return sprintf(buf, format, ##args);			\
 	}								\
@@ -439,6 +477,7 @@ static int xen_vbd_create(struct xen_blkif *blkif, blkif_vdev_t handle,
 static int xen_blkbk_remove(struct xenbus_device *dev)
 {
 	struct backend_info *be = dev_get_drvdata(&dev->dev);
+	int i;
 
 	pr_debug("%s %p %d\n", __func__, dev, dev->otherend_id);
 
@@ -455,7 +494,8 @@ static int xen_blkbk_remove(struct xenbus_device *dev)
 
 	if (be->blkif) {
 		xen_blkif_disconnect(be->blkif);
-		xen_blkif_put(be->blkif);
+		for (i = 0; i < be->blkif->nr_rings; i++)
+			xen_blkif_put(be->blkif);
 	}
 
 	kfree(be->mode);
@@ -839,20 +879,16 @@ again:
 }
 
 
-static int connect_ring(struct backend_info *be)
+static int read_per_ring_refs(struct xen_blkif_ring *ring, const char *dir)
 {
-	struct xenbus_device *dev = be->dev;
+	unsigned int ring_page_order, nr_grefs, evtchn;
 	unsigned int ring_ref[XENBUS_MAX_RING_PAGES];
-	unsigned int evtchn, nr_grefs, ring_page_order;
-	unsigned int pers_grants;
-	char protocol[64] = "";
 	struct pending_req *req, *n;
 	int err, i, j;
-	struct xen_blkif_ring *ring = &be->blkif->ring;
-
-	pr_debug("%s %s\n", __func__, dev->otherend);
+	struct xen_blkif *blkif = ring->blkif;
+	struct xenbus_device *dev = blkif->be->dev;
 
-	err = xenbus_scanf(XBT_NIL, dev->otherend, "event-channel", "%u",
+	err = xenbus_scanf(XBT_NIL, dir, "event-channel", "%u",
 			  &evtchn);
 	if (err != 1) {
 		err = -EINVAL;
@@ -860,12 +896,11 @@ static int connect_ring(struct backend_info *be)
 				 dev->otherend);
 		return err;
 	}
-	pr_info("event-channel %u\n", evtchn);
 
 	err = xenbus_scanf(XBT_NIL, dev->otherend, "ring-page-order", "%u",
 			  &ring_page_order);
 	if (err != 1) {
-		err = xenbus_scanf(XBT_NIL, dev->otherend, "ring-ref",
+		err = xenbus_scanf(XBT_NIL, dir, "ring-ref",
 				  "%u", &ring_ref[0]);
 		if (err != 1) {
 			err = -EINVAL;
@@ -874,7 +909,7 @@ static int connect_ring(struct backend_info *be)
 			return err;
 		}
 		nr_grefs = 1;
-		pr_info("%s:using single page: ring-ref %d\n", dev->otherend,
+		pr_info("%s:using single page: ring-ref %d\n", dir,
 			ring_ref[0]);
 	} else {
 		unsigned int i;
@@ -892,7 +927,7 @@ static int connect_ring(struct backend_info *be)
 			char ring_ref_name[RINGREF_NAME_LEN];
 
 			snprintf(ring_ref_name, RINGREF_NAME_LEN, "ring-ref%u", i);
-			err = xenbus_scanf(XBT_NIL, dev->otherend, ring_ref_name,
+			err = xenbus_scanf(XBT_NIL, dir, ring_ref_name,
 					   "%u", &ring_ref[i]);
 			if (err != 1) {
 				err = -EINVAL;
@@ -900,38 +935,12 @@ static int connect_ring(struct backend_info *be)
 						 dev->otherend, ring_ref_name);
 				return err;
 			}
-			pr_info("ring-ref%u: %u\n", i, ring_ref[i]);
+			pr_info("%s: ring-ref%u: %u\n", dir, i, ring_ref[i]);
 		}
 	}
+	blkif->nr_ring_pages = nr_grefs;
 
-	be->blkif->blk_protocol = BLKIF_PROTOCOL_DEFAULT;
-	err = xenbus_gather(XBT_NIL, dev->otherend, "protocol",
-			    "%63s", protocol, NULL);
-	if (err)
-		strcpy(protocol, "unspecified, assuming default");
-	else if (0 == strcmp(protocol, XEN_IO_PROTO_ABI_NATIVE))
-		be->blkif->blk_protocol = BLKIF_PROTOCOL_NATIVE;
-	else if (0 == strcmp(protocol, XEN_IO_PROTO_ABI_X86_32))
-		be->blkif->blk_protocol = BLKIF_PROTOCOL_X86_32;
-	else if (0 == strcmp(protocol, XEN_IO_PROTO_ABI_X86_64))
-		be->blkif->blk_protocol = BLKIF_PROTOCOL_X86_64;
-	else {
-		xenbus_dev_fatal(dev, err, "unknown fe protocol %s", protocol);
-		return -1;
-	}
-	err = xenbus_gather(XBT_NIL, dev->otherend,
-			    "feature-persistent", "%u",
-			    &pers_grants, NULL);
-	if (err)
-		pers_grants = 0;
-
-	be->blkif->vbd.feature_gnt_persistent = pers_grants;
-	be->blkif->vbd.overflow_max_grants = 0;
-	be->blkif->nr_ring_pages = nr_grefs;
-
-	pr_info("ring-pages:%d, event-channel %d, protocol %d (%s) %s\n",
-		nr_grefs, evtchn, be->blkif->blk_protocol, protocol,
-		pers_grants ? "persistent grants" : "");
+	pr_info("ring-pages:%d, event-channel %d.\n", nr_grefs, evtchn);
 
 	for (i = 0; i < nr_grefs * XEN_BLKIF_REQS_PER_PAGE; i++) {
 		req = kzalloc(sizeof(*req), GFP_KERNEL);
@@ -976,6 +985,71 @@ fail:
 		kfree(req);
 	}
 	return -ENOMEM;
+
+}
+
+static int connect_ring(struct backend_info *be)
+{
+	struct xenbus_device *dev = be->dev;
+	unsigned int pers_grants;
+	char protocol[64] = "";
+	int err, i;
+	char *xspath;
+	size_t xspathsize;
+	const size_t xenstore_path_ext_size = 11; /* sufficient for "/queue-NNN" */
+
+	pr_debug("%s %s\n", __func__, dev->otherend);
+
+	be->blkif->blk_protocol = BLKIF_PROTOCOL_DEFAULT;
+	err = xenbus_gather(XBT_NIL, dev->otherend, "protocol",
+			    "%63s", protocol, NULL);
+	if (err)
+		strcpy(protocol, "unspecified, assuming default");
+	else if (0 == strcmp(protocol, XEN_IO_PROTO_ABI_NATIVE))
+		be->blkif->blk_protocol = BLKIF_PROTOCOL_NATIVE;
+	else if (0 == strcmp(protocol, XEN_IO_PROTO_ABI_X86_32))
+		be->blkif->blk_protocol = BLKIF_PROTOCOL_X86_32;
+	else if (0 == strcmp(protocol, XEN_IO_PROTO_ABI_X86_64))
+		be->blkif->blk_protocol = BLKIF_PROTOCOL_X86_64;
+	else {
+		xenbus_dev_fatal(dev, err, "unknown fe protocol %s", protocol);
+		return -1;
+	}
+	err = xenbus_gather(XBT_NIL, dev->otherend,
+			    "feature-persistent", "%u",
+			    &pers_grants, NULL);
+	if (err)
+		pers_grants = 0;
+
+	be->blkif->vbd.feature_gnt_persistent = pers_grants;
+	be->blkif->vbd.overflow_max_grants = 0;
+
+	pr_info("nr_rings:%d protocol %d (%s) %s\n", be->blkif->nr_rings,
+		 be->blkif->blk_protocol, protocol,
+		 pers_grants ? "persistent grants" : "");
+
+	if (be->blkif->nr_rings == 1)
+		return read_per_ring_refs(&be->blkif->rings[0], dev->otherend);
+	else {
+		xspathsize = strlen(dev->otherend) + xenstore_path_ext_size;
+		xspath = kmalloc(xspathsize, GFP_KERNEL);
+		if (!xspath) {
+			xenbus_dev_fatal(dev, -ENOMEM, "reading ring references");
+			return -ENOMEM;
+		}
+
+		for (i = 0; i < be->blkif->nr_rings; i++) {
+			memset(xspath, 0, xspathsize);
+			snprintf(xspath, xspathsize, "%s/queue-%u", dev->otherend, i);
+			err = read_per_ring_refs(&be->blkif->rings[i], xspath);
+			if (err) {
+				kfree(xspath);
+				return err;
+			}
+		}
+		kfree(xspath);
+	}
+	return 0;
 }
 
 static const struct xenbus_device_id xen_blkbk_ids[] = {
-- 
1.8.3.1

