PCI: Return error if cannot probe VF

Commit 0e7df224 ("PCI: Add sysfs sriov_drivers_autoprobe to control
VF driver binding") allows the user to specify that drivers for VFs of
a PF should not be probed, but it actually causes pci_device_probe() to
return success back to the driver core in this case.  Therefore by all
sysfs appearances the device is bound to a driver, the driver link from
the device exists as does the device link back from the driver, yet the
driver's probe function is never called on the device.  We also fail to
do any sort of cleanup when we're prohibited from probing the device,
the IRQ setup remains in place and we even hold a device reference.

Instead, abort with errno before any setup or references are taken when
pci_device_can_probe() prevents us from trying to probe the device.

Link: https://lore.kernel.org/lkml/155672991496.20698.4279330795743262888.stgit@gimli.home
Fixes: 0e7df224 ("PCI: Add sysfs sriov_drivers_autoprobe to control VF driver binding")
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

drivers/pci/pci-driver.c

@@ -414,6 +414,9 @@ static int pci_device_probe(struct device *dev)
 	struct pci_dev *pci_dev = to_pci_dev(dev);
 	struct pci_driver *drv = to_pci_driver(dev->driver);
 
+	if (!pci_device_can_probe(pci_dev))
+		return -ENODEV;
+
 	pci_assign_irq(pci_dev);
 
 	error = pcibios_alloc_irq(pci_dev);
@@ -421,13 +424,11 @@ static int pci_device_probe(struct device *dev)
 		return error;
 
 	pci_dev_get(pci_dev);
-	if (pci_device_can_probe(pci_dev)) {
 	error = __pci_device_probe(drv, pci_dev);
 	if (error) {
 		pcibios_free_irq(pci_dev);
 		pci_dev_put(pci_dev);
 	}
-	}
 
 	return error;
 }