firewire: enforce access order between generation and node ID, fix "giving up on config rom"

fw_device.node_id and fw_device.generation are accessed without mutexes.
We have to ensure that all readers will get to see node_id updates
before generation updates.

Fixes an inability to recognize devices after "giving up on config rom",
https://bugzilla.redhat.com/show_bug.cgi?id=429950

Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>

Reviewed by Nick Piggin <nickpiggin@yahoo.com.au>.

Verified to fix 'giving up on config rom' issues on multiple system and
drive combinations that were previously affected.

Signed-off-by: Jarod Wilson <jwilson@redhat.com>
Signed-off-by: Kristian Høgsberg <krh@redhat.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/drivers/firewire/fw-sbp2.c b/drivers/firewire/fw-sbp2.c
index d406c34fd378..705a20ce6b4a 100644
--- a/drivers/firewire/fw-sbp2.c
+++ b/drivers/firewire/fw-sbp2.c
@@ -40,6 +40,7 @@
 #include <linux/stringify.h>
 #include <linux/timer.h>
 #include <linux/workqueue.h>
+#include <asm/system.h>
 
 #include <scsi/scsi.h>
 #include <scsi/scsi_cmnd.h>
@@ -662,6 +663,7 @@ static void sbp2_login(struct work_struct *work)
         int generation, node_id, local_node_id;
 
         generation    = device->generation;
+        smp_rmb();    /* node_id must not be older than generation */
         node_id       = device->node_id;
         local_node_id = device->card->node_id;
 
@@ -912,6 +914,7 @@ static void sbp2_reconnect(struct work_struct *work)
         int generation, node_id, local_node_id;
 
         generation    = device->generation;
+        smp_rmb();    /* node_id must not be older than generation */
         node_id       = device->node_id;
         local_node_id = device->card->node_id;