1 files changed, 62 insertions, 20 deletions

diff --git a/drivers/xen/xenbus/xenbus_client.c b/drivers/xen/xenbus/xenbus_client.c
index df6890681231..d6fdd2d209d3 100644
--- a/drivers/xen/xenbus/xenbus_client.c
+++ b/drivers/xen/xenbus/xenbus_client.c
@@ -363,50 +363,92 @@ static void xenbus_switch_fatal(struct xenbus_device *dev, int depth, int err,
 		__xenbus_switch_state(dev, XenbusStateClosing, 1);
 }
 
-/**
- * xenbus_grant_ring
+/*
+ * xenbus_setup_ring
  * @dev: xenbus device
- * @vaddr: starting virtual address of the ring
+ * @vaddr: pointer to starting virtual address of the ring
  * @nr_pages: number of pages to be granted
  * @grefs: grant reference array to be filled in
  *
- * Grant access to the given @vaddr to the peer of the given device.
- * Then fill in @grefs with grant references.  Return 0 on success, or
- * -errno on error.  On error, the device will switch to
- * XenbusStateClosing, and the error will be saved in the store.
+ * Allocate physically contiguous pages for a shared ring buffer and grant it
+ * to the peer of the given device. The ring buffer is initially filled with
+ * zeroes. The virtual address of the ring is stored at @vaddr and the
+ * grant references are stored in the @grefs array. In case of error @vaddr
+ * will be set to NULL and @grefs will be filled with INVALID_GRANT_REF.
  */
-int xenbus_grant_ring(struct xenbus_device *dev, void *vaddr,
+int xenbus_setup_ring(struct xenbus_device *dev, gfp_t gfp, void **vaddr,
 		      unsigned int nr_pages, grant_ref_t *grefs)
 {
-	int err;
-	unsigned int i;
+	unsigned long ring_size = nr_pages * XEN_PAGE_SIZE;
 	grant_ref_t gref_head;
+	unsigned int i;
+	int ret;
 
-	err = gnttab_alloc_grant_references(nr_pages, &gref_head);
-	if (err) {
-		xenbus_dev_fatal(dev, err, "granting access to ring page");
-		return err;
+	*vaddr = alloc_pages_exact(ring_size, gfp | __GFP_ZERO);
+	if (!*vaddr) {
+		ret = -ENOMEM;
+		goto err;
+	}
+
+	ret = gnttab_alloc_grant_references(nr_pages, &gref_head);
+	if (ret) {
+		xenbus_dev_fatal(dev, ret, "granting access to %u ring pages",
+				 nr_pages);
+		goto err;
 	}
 
 	for (i = 0; i < nr_pages; i++) {
 		unsigned long gfn;
 
-		if (is_vmalloc_addr(vaddr))
-			gfn = pfn_to_gfn(vmalloc_to_pfn(vaddr));
+		if (is_vmalloc_addr(*vaddr))
+			gfn = pfn_to_gfn(vmalloc_to_pfn(vaddr[i]));
 		else
-			gfn = virt_to_gfn(vaddr);
+			gfn = virt_to_gfn(vaddr[i]);
 
 		grefs[i] = gnttab_claim_grant_reference(&gref_head);
 		gnttab_grant_foreign_access_ref(grefs[i], dev->otherend_id,
 						gfn, 0);
-
-		vaddr = vaddr + XEN_PAGE_SIZE;
 	}
 
 	return 0;
+
+ err:
+	if (*vaddr)
+		free_pages_exact(*vaddr, ring_size);
+	for (i = 0; i < nr_pages; i++)
+		grefs[i] = INVALID_GRANT_REF;
+	*vaddr = NULL;
+
+	return ret;
 }
-EXPORT_SYMBOL_GPL(xenbus_grant_ring);
+EXPORT_SYMBOL_GPL(xenbus_setup_ring);
 
+/*
+ * xenbus_teardown_ring
+ * @vaddr: starting virtual address of the ring
+ * @nr_pages: number of pages
+ * @grefs: grant reference array
+ *
+ * Remove grants for the shared ring buffer and free the associated memory.
+ * On return the grant reference array is filled with INVALID_GRANT_REF.
+ */
+void xenbus_teardown_ring(void **vaddr, unsigned int nr_pages,
+			  grant_ref_t *grefs)
+{
+	unsigned int i;
+
+	for (i = 0; i < nr_pages; i++) {
+		if (grefs[i] != INVALID_GRANT_REF) {
+			gnttab_end_foreign_access(grefs[i], 0);
+			grefs[i] = INVALID_GRANT_REF;
+		}
+	}
+
+	if (*vaddr)
+		free_pages_exact(*vaddr, nr_pages * XEN_PAGE_SIZE);
+	*vaddr = NULL;
+}
+EXPORT_SYMBOL_GPL(xenbus_teardown_ring);
 
 /**
  * Allocate an event channel for the given xenbus_device, assigning the newly