libfcoe: Make fcoe_sysfs optional / fix fnic NULL exception

fnic doesn't use any of the create/destroy/enable/disable interfaces
either from the (legacy) module paramaters or the (new) fcoe_sysfs
interfaces. When fcoe_sysfs was introduced fnic wasn't changed since
it wasn't using the interfaces. libfcoe incorrectly assumed that that
all of its users were using fcoe_sysfs and when adding and deleting
FCFs would assume the existance of a fcoe_ctlr_device. fnic was not
allocating this structure because it doesn't care about the standard
user interfaces (fnic starts on link only). If/When libfcoe tried to use
the fcoe_ctlr_device's lock for the first time a NULL pointer exception
would be triggered.

Since fnic doesn't care about sysfs or user interfaces, the solution
is to drop libfcoe's assumption that all drivers are using fcoe_sysfs.

This patch accomplishes this by changing some of the structure
relationships.

We need a way to determine when a LLD is using fcoe_sysfs or not and
we can do that by checking for the existance of the fcoe_ctlr_device.
Prior to this patch, it was assumed that the fcoe_ctlr structure was
allocated with the fcoe_ctlr_device and immediately followed it in
memory. To reach the fcoe_ctlr_device we would simply go back in memory
from the fcoe_ctlr to get the fcoe_ctlr_device.

Since fnic doesn't allocate the fcoe_ctlr_device, we cannot keep that
assumption. This patch adds a pointer from the fcoe_ctlr to the
fcoe_ctlr_device. For bnx2fc and fcoe we will continue to allocate the
two structures together, but then we'll set the ctlr->cdev pointer
to point at the fcoe_ctlr_device. fnic will not change and will continue
to allocate the fcoe_ctlr itself, and ctlr->cdev will remain NULL.

When libfcoe adds fcoe_fcf's to the fcoe_ctlr it will check if ctlr->cdev
is set and only if so will it continue to interact with fcoe_sysfs.

Signed-off-by: Robert Love <robert.w.love@intel.com>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Tested-by: Hiral Patel <hiralpat@cisco.com>

3 files changed, 65 insertions, 31 deletions

diff --git a/drivers/scsi/bnx2fc/bnx2fc_fcoe.c b/drivers/scsi/bnx2fc/bnx2fc_fcoe.c
index 69ac55495c1d..27f2cc4b97a5 100644
--- a/drivers/scsi/bnx2fc/bnx2fc_fcoe.c
+++ b/drivers/scsi/bnx2fc/bnx2fc_fcoe.c
@@ -1381,6 +1381,7 @@ struct bnx2fc_interface *bnx2fc_interface_create(struct bnx2fc_hba *hba,
                 return NULL;
         }
         ctlr = fcoe_ctlr_device_priv(ctlr_dev);
+        ctlr->cdev = ctlr_dev;
         interface = fcoe_ctlr_priv(ctlr);
         dev_hold(netdev);
         kref_init(&interface->kref);
diff --git a/drivers/scsi/fcoe/fcoe.c b/drivers/scsi/fcoe/fcoe.c
index dff40b2fccbd..8626988e12a5 100644
--- a/drivers/scsi/fcoe/fcoe.c
+++ b/drivers/scsi/fcoe/fcoe.c
@@ -408,6 +408,7 @@ static struct fcoe_interface *fcoe_interface_create(struct net_device *netdev,
         }
 
         ctlr = fcoe_ctlr_device_priv(ctlr_dev);
+        ctlr->cdev = ctlr_dev;
         fcoe = fcoe_ctlr_priv(ctlr);
 
         dev_hold(netdev);
diff --git a/drivers/scsi/fcoe/fcoe_ctlr.c b/drivers/scsi/fcoe/fcoe_ctlr.c
index 692c6535fe75..75efdbc54ef8 100644
--- a/drivers/scsi/fcoe/fcoe_ctlr.c
+++ b/drivers/scsi/fcoe/fcoe_ctlr.c
@@ -160,10 +160,16 @@ void fcoe_ctlr_init(struct fcoe_ctlr *fip, enum fip_state mode)
 }
 EXPORT_SYMBOL(fcoe_ctlr_init);
 
+/**
+ * fcoe_sysfs_fcf_add() - Add a fcoe_fcf{,_device} to a fcoe_ctlr{,_device}
+ * @new: The newly discovered FCF
+ *
+ * Called with fip->ctlr_mutex held
+ */
 static int fcoe_sysfs_fcf_add(struct fcoe_fcf *new)
 {
         struct fcoe_ctlr *fip = new->fip;
-        struct fcoe_ctlr_device *ctlr_dev = fcoe_ctlr_to_ctlr_dev(fip);
+        struct fcoe_ctlr_device *ctlr_dev;
         struct fcoe_fcf_device *temp, *fcf_dev;
         int rc = -ENOMEM;
 
@@ -174,8 +180,6 @@ static int fcoe_sysfs_fcf_add(struct fcoe_fcf *new)
         if (!temp)
                 goto out;
 
-        mutex_lock(&ctlr_dev->lock);
-
         temp->fabric_name = new->fabric_name;
         temp->switch_name = new->switch_name;
         temp->fc_map = new->fc_map;
@@ -185,55 +189,83 @@ static int fcoe_sysfs_fcf_add(struct fcoe_fcf *new)
         temp->fka_period = new->fka_period;
         temp->selected = 0; /* default to unselected */
 
-        fcf_dev = fcoe_fcf_device_add(ctlr_dev, temp);
-        if (unlikely(!fcf_dev))
-                goto unlock;
-
         /*
-         * The fcoe_sysfs layer can return a CONNECTED fcf that
-         * has a priv (fcf was never deleted) or a CONNECTED fcf
-         * that doesn't have a priv (fcf was deleted). However,
-         * libfcoe will always delete FCFs before trying to add
-         * them. This is ensured because both recv_adv and
-         * age_fcfs are protected by the the fcoe_ctlr's mutex.
-         * This means that we should never get a FCF with a
-         * non-NULL priv pointer.
+         * If ctlr_dev doesn't exist then it means we're a libfcoe user
+         * who doesn't use fcoe_syfs and didn't allocate a fcoe_ctlr_device.
+         * fnic would be an example of a driver with this behavior. In this
+         * case we want to add the fcoe_fcf to the fcoe_ctlr list, but we
+         * don't want to make sysfs changes.
          */
-        BUG_ON(fcf_dev->priv);
 
-        fcf_dev->priv = new;
-        new->fcf_dev = fcf_dev;
+        ctlr_dev = fcoe_ctlr_to_ctlr_dev(fip);
+        if (ctlr_dev) {
+                mutex_lock(&ctlr_dev->lock);
+                fcf_dev = fcoe_fcf_device_add(ctlr_dev, temp);
+                if (unlikely(!fcf_dev)) {
+                        rc = -ENOMEM;
+                        goto out;
+                }
+
+                /*
+                 * The fcoe_sysfs layer can return a CONNECTED fcf that
+                 * has a priv (fcf was never deleted) or a CONNECTED fcf
+                 * that doesn't have a priv (fcf was deleted). However,
+                 * libfcoe will always delete FCFs before trying to add
+                 * them. This is ensured because both recv_adv and
+                 * age_fcfs are protected by the the fcoe_ctlr's mutex.
+                 * This means that we should never get a FCF with a
+                 * non-NULL priv pointer.
+                 */
+                BUG_ON(fcf_dev->priv);
+
+                fcf_dev->priv = new;
+                new->fcf_dev = fcf_dev;
+                mutex_unlock(&ctlr_dev->lock);
+        }
 
         list_add(&new->list, &fip->fcfs);
         fip->fcf_count++;
         rc = 0;
 
-unlock:
-        mutex_unlock(&ctlr_dev->lock);
-
 out:
         kfree(temp);
         return rc;
 }
 
+/**
+ * fcoe_sysfs_fcf_del() - Remove a fcoe_fcf{,_device} to a fcoe_ctlr{,_device}
+ * @new: The FCF to be removed
+ *
+ * Called with fip->ctlr_mutex held
+ */
 static void fcoe_sysfs_fcf_del(struct fcoe_fcf *new)
 {
         struct fcoe_ctlr *fip = new->fip;
-        struct fcoe_ctlr_device *ctlr_dev = fcoe_ctlr_to_ctlr_dev(fip);
+        struct fcoe_ctlr_device *cdev;
         struct fcoe_fcf_device *fcf_dev;
 
         list_del(&new->list);
         fip->fcf_count--;
 
-        mutex_lock(&ctlr_dev->lock);
-
-        fcf_dev = fcoe_fcf_to_fcf_dev(new);
-        WARN_ON(!fcf_dev);
-        new->fcf_dev = NULL;
-        fcoe_fcf_device_delete(fcf_dev);
-        kfree(new);
-
-        mutex_unlock(&ctlr_dev->lock);
+        /*
+         * If ctlr_dev doesn't exist then it means we're a libfcoe user
+         * who doesn't use fcoe_syfs and didn't allocate a fcoe_ctlr_device
+         * or a fcoe_fcf_device.
+         *
+         * fnic would be an example of a driver with this behavior. In this
+         * case we want to remove the fcoe_fcf from the fcoe_ctlr list (above),
+         * but we don't want to make sysfs changes.
+         */
+        cdev = fcoe_ctlr_to_ctlr_dev(fip);
+        if (cdev) {
+                mutex_lock(&cdev->lock);
+                fcf_dev = fcoe_fcf_to_fcf_dev(new);
+                WARN_ON(!fcf_dev);
+                new->fcf_dev = NULL;
+                fcoe_fcf_device_delete(fcf_dev);
+                kfree(new);
+                mutex_unlock(&cdev->lock);
+        }
 }
 
 /**