[Xen-devel] [PATCH 4/7] xen/9pfs: connect to the backend

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

Implement functions to handle the xenbus handshake. Upon connection,
allocate the rings according to the protocol specification.

Initialize a work_struct and a wait_queue. The work_struct will be used
to schedule work upon receiving an event channel notification from the
backend. The wait_queue will be used to wait when the ring is full and
we need to send a new request.

Signed-off-by: Stefano Stabellini <stefano@xxxxxxxxxxx>
CC: boris.ostrovsky@xxxxxxxxxx
CC: jgross@xxxxxxxx
CC: Eric Van Hensbergen <ericvh@xxxxxxxxx>
CC: Ron Minnich <rminnich@xxxxxxxxxx>
CC: Latchesar Ionkov <lucho@xxxxxxxxxx>
CC: v9fs-developer@xxxxxxxxxxxxxxxxxxxxx
---
 net/9p/trans_xen.c | 227 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 227 insertions(+)

diff --git a/net/9p/trans_xen.c b/net/9p/trans_xen.c
index 877dfd0..9f6cf8d 100644
--- a/net/9p/trans_xen.c
+++ b/net/9p/trans_xen.c
@@ -17,6 +17,36 @@
 #include <net/9p/client.h>
 #include <net/9p/transport.h>
 
+#define XEN_9PFS_NUM_RINGS 2
+
+/* One per ring, more than one per 9pfs share */
+struct xen_9pfs_dataring {
+       struct xen_9pfs_front_priv *priv;
+
+       struct xen_9pfs_data_intf *intf;
+       grant_ref_t ref;
+       int evtchn;
+       int irq;
+       spinlock_t lock;
+
+       void *bytes;
+       struct xen_9pfs_data ring;
+       wait_queue_head_t wq;
+       struct work_struct work;
+};
+
+/* One per 9pfs share */
+struct xen_9pfs_front_priv {
+       struct list_head list;
+       struct xenbus_device *dev;
+       char *tag;
+       struct p9_client *client;
+
+       int num_rings;
+       struct xen_9pfs_dataring *rings;
+};
+static LIST_HEAD(xen_9pfs_devs);
+
 static int p9_xen_cancel(struct p9_client *client, struct p9_req_t *req)
 {
        return 0;
@@ -36,6 +66,21 @@ static int p9_xen_request(struct p9_client *client, struct 
p9_req_t *p9_req)
        return 0;
 }
 
+static void p9_xen_response(struct work_struct *work)
+{
+}
+
+static irqreturn_t xen_9pfs_front_event_handler(int irq, void *r)
+{
+       struct xen_9pfs_dataring *ring = r;
+       BUG_ON(!ring || !ring->priv->client);
+
+       wake_up_interruptible(&ring->wq);
+       schedule_work(&ring->work);
+
+       return IRQ_HANDLED;
+}
+
 static struct p9_trans_module p9_xen_trans = {
        .name = "xen",
        .maxsize = (1 << (XEN_9PFS_RING_ORDER + XEN_PAGE_SHIFT)),
@@ -52,25 +97,207 @@ static int p9_xen_request(struct p9_client *client, struct 
p9_req_t *p9_req)
        { "" }
 };
 
+static int xen_9pfs_front_free(struct xen_9pfs_front_priv *priv)
+{
+       int i, j;
+
+       list_del(&priv->list);
+
+       for (i = 0; i < priv->num_rings; i++) {
+               if (priv->rings[i].intf == NULL)
+                       break;
+               if (priv->rings[i].irq > 0)
+                       unbind_from_irqhandler(priv->rings[i].irq, priv->dev);
+               if (priv->rings[i].bytes != NULL) {
+                       for (j = 0; j < (1 << XEN_9PFS_RING_ORDER); j++)
+                               
gnttab_end_foreign_access(priv->rings[i].intf->ref[j], 0, 0);
+                       free_pages((unsigned long)priv->rings[i].bytes, 
XEN_9PFS_RING_ORDER);
+               }
+               gnttab_end_foreign_access(priv->rings[i].ref, 0, 0);
+               free_page((unsigned long)priv->rings[i].intf);
+       }
+       kfree(priv->rings);
+       kfree(priv);
+
+       return 0;
+}
+
 static int xen_9pfs_front_remove(struct xenbus_device *dev)
 {
+       int ret;
+       struct xen_9pfs_front_priv *priv = dev_get_drvdata(&dev->dev);
+
+       dev_set_drvdata(&dev->dev, NULL);
+       ret = xen_9pfs_front_free(priv);
+       return ret;
+}
+
+static int xen_9pfs_front_alloc_dataring(struct xenbus_device *dev,
+               struct xen_9pfs_dataring *ring)
+{
+       int i;
+       int ret = -ENOMEM;
+
+       init_waitqueue_head(&ring->wq);
+       spin_lock_init(&ring->lock);
+       INIT_WORK(&ring->work, p9_xen_response);
+
+       ring->intf = (struct xen_9pfs_data_intf *) __get_free_page(GFP_KERNEL | 
__GFP_ZERO);
+       if (!ring->intf)
+               goto error;
+       memset(ring->intf, 0, XEN_PAGE_SIZE);
+       ring->bytes = (void*)__get_free_pages(GFP_KERNEL | __GFP_ZERO, 
XEN_9PFS_RING_ORDER);
+       if (ring->bytes == NULL)
+               goto error;
+       for (i = 0; i < (1 << XEN_9PFS_RING_ORDER); i++)
+               ring->intf->ref[i] = 
gnttab_grant_foreign_access(dev->otherend_id, 
pfn_to_gfn(virt_to_pfn((void*)ring->bytes) + i), 0);
+       ring->ref = gnttab_grant_foreign_access(dev->otherend_id, 
pfn_to_gfn(virt_to_pfn((void*)ring->intf)), 0);
+       ring->ring.in = ring->bytes;
+       ring->ring.out = ring->bytes + XEN_9PFS_RING_SIZE;
+
+       ret = xenbus_alloc_evtchn(dev, &ring->evtchn);
+       if (ret)
+               goto error;
+       ring->irq = bind_evtchn_to_irqhandler(ring->evtchn, 
xen_9pfs_front_event_handler,
+                                       0, "xen_9pfs-frontend", ring);
+       if (ring->irq < 0) {
+               xenbus_free_evtchn(dev, ring->evtchn);
+               ret = ring->irq;
+               goto error;
+       }
        return 0;
+
+error:
+       if (ring->intf != NULL)
+               kfree(ring->intf);
+       if (ring->bytes != NULL)
+               kfree(ring->bytes);
+       return ret;
 }
 
 static int xen_9pfs_front_probe(struct xenbus_device *dev,
                const struct xenbus_device_id *id)
 {
+       int ret = -EFAULT, i;
+       struct xenbus_transaction xbt;
+       struct xen_9pfs_front_priv *priv = NULL;
+       char *versions;
+       unsigned int max_rings, max_ring_order, len;
+
+       versions = xenbus_read(XBT_NIL, dev->otherend, "versions", &len);
+       if (!len || strcmp(versions, "1"))
+               return -EINVAL;
+       kfree(versions);
+       ret = xenbus_scanf(XBT_NIL, dev->otherend, "max-rings", "%u", 
&max_rings);
+       if (ret < 0 || max_rings < XEN_9PFS_NUM_RINGS)
+               return -EINVAL;
+       ret = xenbus_scanf(XBT_NIL, dev->otherend, "max-ring-page-order", "%u", 
&max_ring_order);
+       if (ret < 0|| max_ring_order < XEN_9PFS_RING_ORDER)
+               return -EINVAL;
+
+
+       priv = kzalloc(sizeof(struct xen_9pfs_front_priv), GFP_KERNEL);
+       if (!priv)
+               return -ENOMEM;
+
+       priv->dev = dev;
+       priv->num_rings = XEN_9PFS_NUM_RINGS;
+       priv->rings = kzalloc(sizeof(struct xen_9pfs_dataring) * 
priv->num_rings,
+                                               GFP_KERNEL);
+       if (!priv->rings) {
+               kfree(priv);
+               return -ENOMEM;
+       }
+
+ again:
+       ret = xenbus_transaction_start(&xbt);
+       if (ret) {
+               xenbus_dev_fatal(dev, ret, "starting transaction");
+               goto error;
+       }
+       ret = xenbus_printf(xbt, dev->nodename, "version", "%u", 1);
+       if (ret)
+               goto error_xenbus;
+       ret = xenbus_printf(xbt, dev->nodename, "num-rings", "%u", 
priv->num_rings);
+       if (ret)
+               goto error_xenbus;
+       for (i = 0; i < priv->num_rings; i++) {
+               char str[16];
+
+               priv->rings[i].priv = priv;
+               ret = xen_9pfs_front_alloc_dataring(dev, &priv->rings[i]);
+               if (ret < 0)
+                       goto error_xenbus;
+
+               sprintf(str, "ring-ref%u", i);
+               ret = xenbus_printf(xbt, dev->nodename, str, "%d", 
priv->rings[i].ref);
+               if (ret)
+                       goto error_xenbus;
+
+               sprintf(str, "event-channel-%u", i);
+               ret = xenbus_printf(xbt, dev->nodename, str, "%u", 
priv->rings[i].evtchn);
+               if (ret)
+                       goto error_xenbus;
+       }
+       priv->tag = xenbus_read(xbt, dev->nodename, "tag", NULL);
+       if (ret)
+               goto error_xenbus;
+       ret = xenbus_transaction_end(xbt, 0);
+       if (ret) {
+               if (ret == -EAGAIN)
+                       goto again;
+               xenbus_dev_fatal(dev, ret, "completing transaction");
+               goto error;
+       }
+
+
+       list_add_tail(&priv->list, &xen_9pfs_devs);
+       dev_set_drvdata(&dev->dev, priv);
+       xenbus_switch_state(dev, XenbusStateInitialised);
+
        return 0;
+
+ error_xenbus:
+       xenbus_transaction_end(xbt, 1);
+       xenbus_dev_fatal(dev, ret, "writing xenstore");
+ error:
+       dev_set_drvdata(&dev->dev, NULL);
+       xen_9pfs_front_free(priv);
+       return ret;
 }
 
 static int xen_9pfs_front_resume(struct xenbus_device *dev)
 {
+       dev_warn(&dev->dev, "suspsend/resume unsupported\n");
        return 0;
 }
 
 static void xen_9pfs_front_changed(struct xenbus_device *dev,
                            enum xenbus_state backend_state)
 {
+       switch (backend_state) {
+       case XenbusStateReconfiguring:
+       case XenbusStateReconfigured:
+       case XenbusStateInitialising:
+       case XenbusStateInitialised:
+       case XenbusStateUnknown:
+               break;
+
+       case XenbusStateInitWait:
+               break;
+
+       case XenbusStateConnected:
+               xenbus_switch_state(dev, XenbusStateConnected);
+               break;
+
+       case XenbusStateClosed:
+               if (dev->state == XenbusStateClosed)
+                       break;
+               /* Missed the backend's CLOSING state -- fallthrough */
+       case XenbusStateClosing:
+               xenbus_frontend_closed(dev);
+               break;
+       }
 }
 
 static struct xenbus_driver xen_9pfs_front_driver = {
-- 
1.9.1


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