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>

1 files changed, 6 insertions, 1 deletions

diff --git a/include/scsi/libfcoe.h b/include/scsi/libfcoe.h
index 4427393115ea..de7e3ee60f0c 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