[SCSI] zfcp: Locking for req_no and req_seq_no

There is a possible race condition while generating the unique
request ids and sequence numbers. Both might be read at the
same time and have the same value. Fix this by serializing the
access through the queue lock of the adapter: First call
zfcp_fsf_req_sbal_get that acquires the lock, then read and
increment the unique ids.

Signed-off-by: Christof Schmitt <christof.schmitt@de.ibm.com>
Signed-off-by: Swen Schillig <swen@vnet.ibm.com>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>

1 files changed, 8 insertions, 9 deletions

diff --git a/drivers/s390/scsi/zfcp_fsf.c b/drivers/s390/scsi/zfcp_fsf.c
index f120b16c77d5..07094c3dc341 100644
--- a/drivers/s390/scsi/zfcp_fsf.c
+++ b/drivers/s390/scsi/zfcp_fsf.c
@@ -4645,23 +4645,22 @@ zfcp_fsf_req_create(struct zfcp_adapter *adapter, u32 fsf_cmd, int req_flags,
         fsf_req->adapter = adapter;
         fsf_req->fsf_command = fsf_cmd;
         INIT_LIST_HEAD(&fsf_req->list);
-        
-        /* this is serialized (we are holding req_queue-lock of adapter */
-        if (adapter->req_no == 0)
-                adapter->req_no++;
-        fsf_req->req_id = adapter->req_no++;
-
         init_timer(&fsf_req->timer);
-        zfcp_fsf_req_qtcb_init(fsf_req);
 
         /* initialize waitqueue which may be used to wait on 
            this request completion */
         init_waitqueue_head(&fsf_req->completion_wq);
 
         ret = zfcp_fsf_req_sbal_get(adapter, req_flags, lock_flags);
-        if(ret < 0) {
+        if (ret < 0)
                 goto failed_sbals;
-        }
+
+        /* this is serialized (we are holding req_queue-lock of adapter) */
+        if (adapter->req_no == 0)
+                adapter->req_no++;
+        fsf_req->req_id = adapter->req_no++;
+
+        zfcp_fsf_req_qtcb_init(fsf_req);
 
         /*
          * We hold queue_lock here. Check if QDIOUP is set and let request fail