xen/blkback: pseudo support for multi hardware queues/rings

Preparatory patch for multiple hardware queues (rings). The number of
rings is unconditionally set to 1, larger number will be enabled in
"xen/blkback: get the number of hardware queues/rings from blkfront".

Signed-off-by: Arianna Avanzini <avanzini.arianna@gmail.com>
Signed-off-by: Bob Liu <bob.liu@oracle.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
---
v2: Align variables in the structures.

2 files changed, 175 insertions, 105 deletions

diff --git a/drivers/block/xen-blkback/common.h b/drivers/block/xen-blkback/common.h
index dbdf4164c83f..310eff3cf43f 100644
--- a/drivers/block/xen-blkback/common.h
+++ b/drivers/block/xen-blkback/common.h
@@ -340,7 +340,8 @@ 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 e4bfc928035d..f5bfedd0e948 100644
--- a/drivers/block/xen-blkback/xenbus.c
+++ b/drivers/block/xen-blkback/xenbus.c
@@ -86,9 +86,11 @@ static void xen_update_blkif_status(struct xen_blkif *blkif)
 {
         int err;
         char name[BLKBACK_NAME_LEN];
+        struct xen_blkif_ring *ring;
+        int i;
 
         /* 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 +115,55 @@ 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;
+        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_fatal(blkif->be->dev, err,
+                                        "start %s-%d xenblkd", name, i);
+                        goto out;
+                }
+        }
+        return;
+
+out:
+        while (--i >= 0) {
+                ring = &blkif->rings[i];
+                kthread_stop(ring->xenblkd);
         }
+        return;
+}
+
+static int xen_blkif_alloc_rings(struct xen_blkif *blkif)
+{
+        unsigned 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);
 
@@ -143,15 +181,11 @@ static struct xen_blkif *xen_blkif_alloc(domid_t domid)
         blkif->st_print = jiffies;
         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);
-
-        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;
 }
@@ -216,50 +250,54 @@ 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;
+        unsigned 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];
+                unsigned 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;
@@ -279,6 +317,7 @@ 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);
 }
 
@@ -427,6 +466,7 @@ 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);
+        unsigned int i;
 
         pr_debug("%s %p %d\n", __func__, dev, dev->otherend_id);
 
@@ -443,7 +483,8 @@ 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);
@@ -826,51 +867,43 @@ again:
         xenbus_transaction_end(xbt, 1);
 }
 
-
-static int connect_ring(struct backend_info *be)
+/*
+ * Each ring may have multi pages, depends on "ring-page-order".
+ */
+static int read_per_ring_refs(struct xen_blkif_ring *ring, const char *dir)
 {
-        struct xenbus_device *dev = be->dev;
         unsigned int ring_ref[XENBUS_MAX_RING_GRANTS];
-        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;
+        unsigned int ring_page_order, nr_grefs, evtchn;
 
-        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;
-                xenbus_dev_fatal(dev, err, "reading %s/event-channel",
-                                 dev->otherend);
+                xenbus_dev_fatal(dev, err, "reading %s/event-channel", dir);
                 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",
-                                  "%u", &ring_ref[0]);
+                err = xenbus_scanf(XBT_NIL, dir, "ring-ref", "%u", &ring_ref[0]);
                 if (err != 1) {
                         err = -EINVAL;
-                        xenbus_dev_fatal(dev, err, "reading %s/ring-ref",
-                                         dev->otherend);
+                        xenbus_dev_fatal(dev, err, "reading %s/ring-ref", dir);
                         return err;
                 }
                 nr_grefs = 1;
-                pr_info("%s:using single page: ring-ref %d\n", dev->otherend,
-                        ring_ref[0]);
         } else {
                 unsigned int i;
 
                 if (ring_page_order > xen_blkif_max_ring_order) {
                         err = -EINVAL;
                         xenbus_dev_fatal(dev, err, "%s/request %d ring page order exceed max:%d",
-                                         dev->otherend, ring_page_order,
+                                         dir, ring_page_order,
                                          xen_blkif_max_ring_order);
                         return err;
                 }
@@ -880,46 +913,17 @@ 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;
                                 xenbus_dev_fatal(dev, err, "reading %s/%s",
-                                                 dev->otherend, ring_ref_name);
+                                                 dir, ring_ref_name);
                                 return err;
                         }
-                        pr_info("ring-ref%u: %u\n", i, ring_ref[i]);
                 }
         }
-
-        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" : "");
+        blkif->nr_ring_pages = nr_grefs;
 
         for (i = 0; i < nr_grefs * XEN_BLKIF_REQS_PER_PAGE; i++) {
                 req = kzalloc(sizeof(*req), GFP_KERNEL);
@@ -964,6 +968,71 @@ 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("%s: using %d queues, protocol %d (%s) %s\n", dev->nodename,
+                 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[] = {