[SCSI] ibmvscsi: Prevent IO during partner login

By setting the request_limit in send_srp_login to 1 we allowed login
requests to be sent to the server adapter.  If this was not an initial
login, but was a login after a disconnect with the server, other I/O
requests could attempt to be processed before the login occured.  These
I/O requests would fail, sometimes resulting in filesystems getting
marked read-only.

To address this we can set the request_limit to 0 while doing the login
and add an exception where login requests, along with task management
events, are always passed to the server.

There is a case where the request_limit had already reached 0 would result
in all events being sent rather than returning SCSI_MLQUEUE_HOST_BUSY; this
has also been fixed by this patch.

Signed-off-by: Robert Jennings <rcj@linux.vnet.ibm.com>
Signed-off-by: Brian King <brking@linux.vnet.ibm.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>

diff --git a/drivers/scsi/ibmvscsi/ibmvscsi.c b/drivers/scsi/ibmvscsi/ibmvscsi.c
index 22d91ee173c594f1d101f6f1d97e9395aac00ccb..5f2396c03958924393864718485d1de683bda6b1 100644 (file)
--- a/drivers/scsi/ibmvscsi/ibmvscsi.c
+++ b/drivers/scsi/ibmvscsi/ibmvscsi.c
@@ -556,7 +556,7 @@ static int ibmvscsi_send_srp_event(struct srp_event_struct *evt_struct,
                                   unsigned long timeout)
 {
        u64 *crq_as_u64 = (u64 *) &evt_struct->crq;
-       int request_status;
+       int request_status = 0;
        int rc;
 
        /* If we have exhausted our request limit, just fail this request,
@@ -574,6 +574,13 @@ static int ibmvscsi_send_srp_event(struct srp_event_struct *evt_struct,
                if (request_status < -1)
                        goto send_error;
                /* Otherwise, we may have run out of requests. */
+               /* If request limit was 0 when we started the adapter is in the
+                * process of performing a login with the server adapter, or
+                * we may have run out of requests.
+                */
+               else if (request_status == -1 &&
+                        evt_struct->iu.srp.login_req.opcode != SRP_LOGIN_REQ)
+                       goto send_busy;
                /* Abort and reset calls should make it through.
                 * Nothing except abort and reset should use the last two
                 * slots unless we had two or less to begin with.
@@ -633,7 +640,8 @@ static int ibmvscsi_send_srp_event(struct srp_event_struct *evt_struct,
        unmap_cmd_data(&evt_struct->iu.srp.cmd, evt_struct, hostdata->dev);
 
        free_event_struct(&hostdata->pool, evt_struct);
-       atomic_inc(&hostdata->request_limit);
+       if (request_status != -1)
+               atomic_inc(&hostdata->request_limit);
        return SCSI_MLQUEUE_HOST_BUSY;
 
  send_error:
@@ -927,10 +935,11 @@ static int send_srp_login(struct ibmvscsi_host_data *hostdata)
        login->req_buf_fmt = SRP_BUF_FORMAT_DIRECT | SRP_BUF_FORMAT_INDIRECT;
        
        spin_lock_irqsave(hostdata->host->host_lock, flags);
-       /* Start out with a request limit of 1, since this is negotiated in
-        * the login request we are just sending
+       /* Start out with a request limit of 0, since this is negotiated in
+        * the login request we are just sending and login requests always
+        * get sent by the driver regardless of request_limit.
         */
-       atomic_set(&hostdata->request_limit, 1);
+       atomic_set(&hostdata->request_limit, 0);
 
        rc = ibmvscsi_send_srp_event(evt_struct, hostdata, init_timeout * 2);
        spin_unlock_irqrestore(hostdata->host->host_lock, flags);