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Subject[PATCH] firewire: fw-sbp2: enforce read order of device generation and node ID
Two fixes:
- There was a small window where a login or reconnect job could use an
already updated card generation with an outdated node ID. We better
use the fw_device.generation here, not the fw_card.generation.
- Insert a memory barrier to ensure that the device generation is read
before the node ID. This is to guarantee that the generation is not
newer than the node ID.

A small optimization:
- The target's and initiator's node IDs can be obtained from fw_device
and fw_card. Dereferencing their underlying topology objects is not
necessary.

Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
---
drivers/firewire/fw-sbp2.c | 14 ++++++++------
1 file changed, 8 insertions(+), 6 deletions(-)
Index: linux/drivers/firewire/fw-sbp2.c
===================================================================
--- linux.orig/drivers/firewire/fw-sbp2.c
+++ linux/drivers/firewire/fw-sbp2.c
@@ -643,9 +643,10 @@ static void sbp2_login(struct work_struc
struct sbp2_login_response response;
int generation, node_id, local_node_id;

- generation = device->card->generation;
- node_id = device->node->node_id;
- local_node_id = device->card->local_node->node_id;
+ generation = device->generation;
+ rmb();
+ node_id = device->node_id;
+ local_node_id = device->card->node_id;

if (sbp2_send_management_orb(lu, node_id, generation,
SBP2_LOGIN_REQUEST, lu->lun, &response) < 0) {
@@ -900,9 +901,10 @@ static void sbp2_reconnect(struct work_s
struct fw_device *device = fw_device(unit->device.parent);
int generation, node_id, local_node_id;

- generation = device->card->generation;
- node_id = device->node->node_id;
- local_node_id = device->card->local_node->node_id;
+ generation = device->generation;
+ rmb();
+ node_id = device->node_id;
+ local_node_id = device->card->node_id;

if (sbp2_send_management_orb(lu, node_id, generation,
SBP2_RECONNECT_REQUEST,
--
Stefan Richter
-=====-=-=== =-== ----=
http://arcgraph.de/sr/
-
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