xen/pciback: avoid multiple entries in slot list

The Xen pciback driver has a list of all pci devices it is ready to
seize. There is no check whether a to be added entry already exists.
While this might be no problem in the common case it might confuse
those which consume the list via sysfs.

Modify the handling of this list by not adding an entry which already
exists. As this will be needed later split out the list handling into
a separate function.
Signed-off-by: Juergen Gross <jgross@suse.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>

drivers/xen/xen-pciback/pci_stub.c

@@ -478,6 +478,36 @@ static int __init pcistub_init_devices_late(void)
 	return 0;
 }
 
+static void pcistub_device_id_add_list(struct pcistub_device_id *new,
+				       int domain, int bus, unsigned int devfn)
+{
+	struct pcistub_device_id *pci_dev_id;
+	unsigned long flags;
+	int found = 0;
+
+	spin_lock_irqsave(&device_ids_lock, flags);
+
+	list_for_each_entry(pci_dev_id, &pcistub_device_ids, slot_list) {
+		if (pci_dev_id->domain == domain && pci_dev_id->bus == bus &&
+		    pci_dev_id->devfn == devfn) {
+			found = 1;
+			break;
+		}
+	}
+
+	if (!found) {
+		new->domain = domain;
+		new->bus = bus;
+		new->devfn = devfn;
+		list_add_tail(&new->slot_list, &pcistub_device_ids);
+	}
+
+	spin_unlock_irqrestore(&device_ids_lock, flags);
+
+	if (found)
+		kfree(new);
+}
+
 static int pcistub_seize(struct pci_dev *dev)
 {
 	struct pcistub_device *psdev;
@@ -1012,7 +1042,6 @@ static inline int str_to_quirk(const char *buf, int *domain, int *bus, int
 static int pcistub_device_id_add(int domain, int bus, int slot, int func)
 {
 	struct pcistub_device_id *pci_dev_id;
-	unsigned long flags;
 	int rc = 0, devfn = PCI_DEVFN(slot, func);
 
 	if (slot < 0) {
@@ -1042,16 +1071,10 @@ static int pcistub_device_id_add(int domain, int bus, int slot, int func)
 	if (!pci_dev_id)
 		return -ENOMEM;
 
-	pci_dev_id->domain = domain;
-	pci_dev_id->bus = bus;
-	pci_dev_id->devfn = devfn;
-
 	pr_debug("wants to seize %04x:%02x:%02x.%d\n",
 		 domain, bus, slot, func);
 
-	spin_lock_irqsave(&device_ids_lock, flags);
-	list_add_tail(&pci_dev_id->slot_list, &pcistub_device_ids);
-	spin_unlock_irqrestore(&device_ids_lock, flags);
+	pcistub_device_id_add_list(pci_dev_id, domain, bus, devfn);
 
 	return 0;
 }