ACPI / hotplug / PCI: Simplify disable_slot()

After recent PCI core changes related to the rescan/remove locking,
the ACPIPHP's disable_slot() function is only called under the
general PCI rescan/remove lock, so it doesn't have to use
dev_in_slot() any more to avoid race conditions.  Make it simply
walk the devices on the bus and drop the ones in the slot being
disabled and drop dev_in_slot() which has no more users.

Moreover, to avoid problems described in the changelog of commit
29ed1f29b68a (PCI: pciehp: Fix null pointer deref when hot-removing
SR-IOV device), make disable_slot() carry out the list walk in
reverse order.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Tested-by: Mika Westerberg <mika.westerberg@linux.intel.com>

1 files changed, 5 insertions, 23 deletions

diff --git a/drivers/pci/hotplug/acpiphp_glue.c b/drivers/pci/hotplug/acpiphp_glue.c
index e2a783fdb98f..f24c19c8f8c4 100644
--- a/drivers/pci/hotplug/acpiphp_glue.c
+++ b/drivers/pci/hotplug/acpiphp_glue.c
@@ -625,32 +625,15 @@ static void __ref enable_slot(struct acpiphp_slot *slot)
         }
 }
 
-/* return first device in slot, acquiring a reference on it */
-static struct pci_dev *dev_in_slot(struct acpiphp_slot *slot)
-{
-        struct pci_bus *bus = slot->bus;
-        struct pci_dev *dev;
-        struct pci_dev *ret = NULL;
-
-        down_read(&pci_bus_sem);
-        list_for_each_entry(dev, &bus->devices, bus_list)
-                if (PCI_SLOT(dev->devfn) == slot->device) {
-                        ret = pci_dev_get(dev);
-                        break;
-                }
-        up_read(&pci_bus_sem);
-
-        return ret;
-}
-
 /**
  * disable_slot - disable a slot
  * @slot: ACPI PHP slot
  */
 static void disable_slot(struct acpiphp_slot *slot)
 {
+        struct pci_bus *bus = slot->bus;
+        struct pci_dev *dev, *prev;
         struct acpiphp_func *func;
-        struct pci_dev *pdev;
 
         /*
          * enable_slot() enumerates all functions in this device via
@@ -658,10 +641,9 @@ static void disable_slot(struct acpiphp_slot *slot)
          * methods (_EJ0, etc.) or not.  Therefore, we remove all functions
          * here.
          */
-        while ((pdev = dev_in_slot(slot))) {
-                pci_stop_and_remove_bus_device(pdev);
-                pci_dev_put(pdev);
-        }
+        list_for_each_entry_safe_reverse(dev, prev, &bus->devices, bus_list)
+                if (PCI_SLOT(dev->devfn) == slot->device)
+                        pci_stop_and_remove_bus_device(dev);
 
         list_for_each_entry(func, &slot->funcs, sibling)
                 acpiphp_bus_trim(func_to_handle(func));