[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>

1 files changed, 14 insertions, 5 deletions

diff --git a/drivers/scsi/ibmvscsi/ibmvscsi.c b/drivers/scsi/ibmvscsi/ibmvscsi.c
index 22d91ee173c5..5f2396c03958 100644
--- 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);