PCI: Simplify IOV implementation and fix reference count races

Trivial changes to IOV:

  1) use new PCI interfaces to simplify IOV implementation
  2) fix some reference count related race windows

[bhelgaas: fix virtfn_add() add bus/alloc dev error paths]
Signed-off-by: Jiang Liu <jiang.liu@huawei.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Cc: Donald Dutile <ddutile@redhat.com>
Cc: Yinghai Lu <yinghai@kernel.org>
Cc: Ram Pai <linuxram@us.ibm.com>

1 files changed, 24 insertions, 35 deletions

diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c
index 8f1e1174b71f..5fffca995a91 100644
--- a/drivers/pci/iov.c
+++ b/drivers/pci/iov.c
@@ -51,24 +51,16 @@ static struct pci_bus *virtfn_add_bus(struct pci_bus *bus, int busnr)
         return child;
 }
 
-static void virtfn_remove_bus(struct pci_bus *bus, int busnr)
+static void virtfn_remove_bus(struct pci_bus *physbus, struct pci_bus *virtbus)
 {
-        struct pci_bus *child;
-
-        if (bus->number == busnr)
-                return;
-
-        child = pci_find_bus(pci_domain_nr(bus), busnr);
-        BUG_ON(!child);
-
-        if (list_empty(&child->devices))
-                pci_remove_bus(child);
+        if (physbus != virtbus && list_empty(&virtbus->devices))
+                pci_remove_bus(virtbus);
 }
 
 static int virtfn_add(struct pci_dev *dev, int id, int reset)
 {
         int i;
-        int rc;
+        int rc = -ENOMEM;
         u64 size;
         char buf[VIRTFN_ID_LEN];
         struct pci_dev *virtfn;
@@ -76,18 +68,15 @@ static int virtfn_add(struct pci_dev *dev, int id, int reset)
         struct pci_sriov *iov = dev->sriov;
         struct pci_bus *bus;
 
-        virtfn = pci_alloc_dev(NULL);
-        if (!virtfn)
-                return -ENOMEM;
-
         mutex_lock(&iov->dev->sriov->lock);
         bus = virtfn_add_bus(dev->bus, virtfn_bus(dev, id));
-        if (!bus) {
-                kfree(virtfn);
-                mutex_unlock(&iov->dev->sriov->lock);
-                return -ENOMEM;
-        }
-        virtfn->bus = pci_bus_get(bus);
+        if (!bus)
+                goto failed;
+
+        virtfn = pci_alloc_dev(bus);
+        if (!virtfn)
+                goto failed0;
+
         virtfn->devfn = virtfn_devfn(dev, id);
         virtfn->vendor = dev->vendor;
         pci_read_config_word(dev, iov->pos + PCI_SRIOV_VF_DID, &virtfn->device);
@@ -136,7 +125,9 @@ failed1:
         pci_dev_put(dev);
         mutex_lock(&iov->dev->sriov->lock);
         pci_stop_and_remove_bus_device(virtfn);
-        virtfn_remove_bus(dev->bus, virtfn_bus(dev, id));
+failed0:
+        virtfn_remove_bus(dev->bus, bus);
+failed:
         mutex_unlock(&iov->dev->sriov->lock);
 
         return rc;
@@ -145,20 +136,15 @@ failed1:
 static void virtfn_remove(struct pci_dev *dev, int id, int reset)
 {
         char buf[VIRTFN_ID_LEN];
-        struct pci_bus *bus;
         struct pci_dev *virtfn;
         struct pci_sriov *iov = dev->sriov;
 
-        bus = pci_find_bus(pci_domain_nr(dev->bus), virtfn_bus(dev, id));
-        if (!bus)
-                return;
-
-        virtfn = pci_get_slot(bus, virtfn_devfn(dev, id));
+        virtfn = pci_get_domain_bus_and_slot(pci_domain_nr(dev->bus),
+                                             virtfn_bus(dev, id),
+                                             virtfn_devfn(dev, id));
         if (!virtfn)
                 return;
 
-        pci_dev_put(virtfn);
-
         if (reset) {
                 device_release_driver(&virtfn->dev);
                 __pci_reset_function(virtfn);
@@ -176,9 +162,11 @@ static void virtfn_remove(struct pci_dev *dev, int id, int reset)
 
         mutex_lock(&iov->dev->sriov->lock);
         pci_stop_and_remove_bus_device(virtfn);
-        virtfn_remove_bus(dev->bus, virtfn_bus(dev, id));
+        virtfn_remove_bus(dev->bus, virtfn->bus);
         mutex_unlock(&iov->dev->sriov->lock);
 
+        /* balance pci_get_domain_bus_and_slot() */
+        pci_dev_put(virtfn);
         pci_dev_put(dev);
 }
 
@@ -335,13 +323,14 @@ static int sriov_enable(struct pci_dev *dev, int nr_virtfn)
                 if (!pdev)
                         return -ENODEV;
 
-                pci_dev_put(pdev);
-
-                if (!pdev->is_physfn)
+                if (!pdev->is_physfn) {
+                        pci_dev_put(pdev);
                         return -ENODEV;
+                }
 
                 rc = sysfs_create_link(&dev->dev.kobj,
                                         &pdev->dev.kobj, "dep_link");
+                pci_dev_put(pdev);
                 if (rc)
                         return rc;
         }