PCI: Remove spurious error for sriov_numvfs store and simplify flow

If we request "num_vfs" and the driver's sriov_configure() method enables
exactly that number ("num_vfs_enabled"), we complain "Invalid value for
number of VFs to enable" and return an error.  We should silently return
success instead.

Also, use kstrtou16() since numVFs is defined to be a 16-bit field and
rework to simplify control flow.

Reported-by: Greg Rose <gregory.v.rose@intel.com>
Reference: http://lkml.kernel.org/r/20121214101911.00002f59@unknown
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Tested-by: Donald Dutile <ddutile@redhat.com>

1 files changed, 34 insertions, 51 deletions

diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
index 05b78b16d20b..9c6e9bb674ec 100644
--- a/drivers/pci/pci-sysfs.c
+++ b/drivers/pci/pci-sysfs.c
@@ -422,77 +422,60 @@ static ssize_t sriov_numvfs_show(struct device *dev,
 }
 
 /*
- * num_vfs > 0; number of vfs to enable
- * num_vfs = 0; disable all vfs
+ * num_vfs > 0; number of VFs to enable
+ * num_vfs = 0; disable all VFs
  *
  * Note: SRIOV spec doesn't allow partial VF
- *       disable, so its all or none.
+ *       disable, so it's all or none.
  */
 static ssize_t sriov_numvfs_store(struct device *dev,
                                   struct device_attribute *attr,
                                   const char *buf, size_t count)
 {
         struct pci_dev *pdev = to_pci_dev(dev);
-        int num_vfs_enabled = 0;
-        int num_vfs;
-        int ret = 0;
-        u16 total;
+        int ret;
+        u16 num_vfs;
 
-        if (kstrtoint(buf, 0, &num_vfs) < 0)
-                return -EINVAL;
+        ret = kstrtou16(buf, 0, &num_vfs);
+        if (ret < 0)
+                return ret;
+
+        if (num_vfs > pci_sriov_get_totalvfs(pdev))
+                return -ERANGE;
+
+        if (num_vfs == pdev->sriov->num_VFs)
+                return count;           /* no change */
 
         /* is PF driver loaded w/callback */
         if (!pdev->driver || !pdev->driver->sriov_configure) {
-                dev_info(&pdev->dev,
-                         "Driver doesn't support SRIOV configuration via sysfs\n");
+                dev_info(&pdev->dev, "Driver doesn't support SRIOV configuration via sysfs\n");
                 return -ENOSYS;
         }
 
-        /* if enabling vf's ... */
-        total = pci_sriov_get_totalvfs(pdev);
-        /* Requested VFs to enable < totalvfs and none enabled already */
-        if ((num_vfs > 0) && (num_vfs <= total)) {
-                if (pdev->sriov->num_VFs == 0) {
-                        num_vfs_enabled =
-                                pdev->driver->sriov_configure(pdev, num_vfs);
-                        if ((num_vfs_enabled >= 0) &&
-                            (num_vfs_enabled != num_vfs)) {
-                                dev_warn(&pdev->dev,
-                                         "Only %d VFs enabled\n",
-                                         num_vfs_enabled);
-                                return count;
-                        } else if (num_vfs_enabled < 0)
-                                /* error code from driver callback */
-                                return num_vfs_enabled;
-                } else if (num_vfs == pdev->sriov->num_VFs) {
-                        dev_warn(&pdev->dev,
-                                 "%d VFs already enabled; no enable action taken\n",
-                                 num_vfs);
-                        return count;
-                } else {
-                        dev_warn(&pdev->dev,
-                                 "%d VFs already enabled. Disable before enabling %d VFs\n",
-                                 pdev->sriov->num_VFs, num_vfs);
-                        return -EINVAL;
-                }
+        if (num_vfs == 0) {
+                /* disable VFs */
+                ret = pdev->driver->sriov_configure(pdev, 0);
+                if (ret < 0)
+                        return ret;
+                return count;
         }
 
-        /* disable vfs */
-        if (num_vfs == 0) {
-                if (pdev->sriov->num_VFs != 0) {
-                        ret = pdev->driver->sriov_configure(pdev, 0);
-                        return ret ? ret : count;
-                } else {
-                        dev_warn(&pdev->dev,
-                                 "All VFs disabled; no disable action taken\n");
-                        return count;
-                }
+        /* enable VFs */
+        if (pdev->sriov->num_VFs) {
+                dev_warn(&pdev->dev, "%d VFs already enabled. Disable before enabling %d VFs\n",
+                         pdev->sriov->num_VFs, num_vfs);
+                return -EBUSY;
         }
 
-        dev_err(&pdev->dev,
-                "Invalid value for number of VFs to enable: %d\n", num_vfs);
+        ret = pdev->driver->sriov_configure(pdev, num_vfs);
+        if (ret < 0)
+                return ret;
 
-        return -EINVAL;
+        if (ret != num_vfs)
+                dev_warn(&pdev->dev, "%d VFs requested; only %d enabled\n",
+                         num_vfs, ret);
+
+        return count;
 }
 
 static struct device_attribute sriov_totalvfs_attr = __ATTR_RO(sriov_totalvfs);