[PATCH 17/19] libfcoe: Make fcoe_sysfs optional / fix fnic NULL exception

[Robert Love <robert.w.love@intel.com>]

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>
---
 drivers/scsi/bnx2fc/bnx2fc_fcoe.c |    1 
 drivers/scsi/fcoe/fcoe.c          |    1 
 drivers/scsi/fcoe/fcoe_ctlr.c     |   94 +++++++++++++++++++++++++------------
 include/scsi/libfcoe.h            |    7 ++-
 4 files changed, 71 insertions(+), 32 deletions(-)

diff --git a/drivers/scsi/bnx2fc/bnx2fc_fcoe.c b/drivers/scsi/bnx2fc/bnx2fc_fcoe.c
index 69ac554..27f2cc4 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 dff40b2..8626988 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 692c653..75efdbc 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);
+	}
 }
 
 /**
diff --git a/include/scsi/libfcoe.h b/include/scsi/libfcoe.h
index 4427393..de7e3ee 100644
--- a/include/scsi/libfcoe.h
+++ b/include/scsi/libfcoe.h
@@ -90,6 +90,7 @@ enum fip_state {
  * @lp:		   &fc_lport: libfc local port.
  * @sel_fcf:	   currently selected FCF, or NULL.
  * @fcfs:	   list of discovered FCFs.
+ * @cdev:          (Optional) pointer to sysfs fcoe_ctlr_device.
  * @fcf_count:	   number of discovered FCF entries.
  * @sol_time:	   time when a multicast solicitation was last sent.
  * @sel_time:	   time after which to select an FCF.
@@ -127,6 +128,7 @@ struct fcoe_ctlr {
 	struct fc_lport *lp;
 	struct fcoe_fcf *sel_fcf;
 	struct list_head fcfs;
+	struct fcoe_ctlr_device *cdev;
 	u16 fcf_count;
 	unsigned long sol_time;
 	unsigned long sel_time;
@@ -168,8 +170,11 @@ static inline void *fcoe_ctlr_priv(const struct fcoe_ctlr *ctlr)
 	return (void *)(ctlr + 1);
 }
 
+/*
+ * This assumes that the fcoe_ctlr (x) is allocated with the fcoe_ctlr_device.
+ */
 #define fcoe_ctlr_to_ctlr_dev(x)					\
-	(struct fcoe_ctlr_device *)(((struct fcoe_ctlr_device *)(x)) - 1)
+	(x)->cdev
 
 /**
  * struct fcoe_fcf - Fibre-Channel Forwarder