scsi_debug: give unit attention and other errors precedence over TSF

Give existing errors priority over the generation of Task
Set Full (TSF) errors. So that max_queue is not exceeded,
existing errors may be sent back in the invocation thread.
This is done so errors like Unit Attentions are not hidden
and lost by either max_queue exceeded or real/injected
TSFs.

Signed-off-by: Douglas Gilbert <dgilbert@interlog.com>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>

diff --git a/drivers/scsi/scsi_debug.c b/drivers/scsi/scsi_debug.c
index 07d224a..693f2fa 100644 (file)
--- a/drivers/scsi/scsi_debug.c
+++ b/drivers/scsi/scsi_debug.c
@@ -3006,7 +3006,7 @@ schedule_resp(struct scsi_cmnd *cmnd, struct sdebug_dev_info *devip,
              int scsi_result, int delta_jiff)
 {
        unsigned long iflags;
-       int k, num_in_q, tsf, qdepth, inject;
+       int k, num_in_q, qdepth, inject;
        struct sdebug_queued_cmd *sqcp = NULL;
        struct scsi_device *sdp = cmnd->device;
 
@@ -3019,55 +3019,48 @@ schedule_resp(struct scsi_cmnd *cmnd, struct sdebug_dev_info *devip,
        if ((scsi_result) && (SCSI_DEBUG_OPT_NOISE & scsi_debug_opts))
                sdev_printk(KERN_INFO, sdp, "%s: non-zero result=0x%x\n",
                            __func__, scsi_result);
-       if (delta_jiff == 0) {
-               /* using same thread to call back mid-layer */
-               cmnd->result = scsi_result;
-               cmnd->scsi_done(cmnd);
-               return 0;
-       }
+       if (delta_jiff == 0)
+               goto respond_in_thread;
 
-       /* deferred response cases */
+       /* schedule the response at a later time if resources permit */
        spin_lock_irqsave(&queued_arr_lock, iflags);
        num_in_q = atomic_read(&devip->num_in_q);
        qdepth = cmnd->device->queue_depth;
-       k = find_first_zero_bit(queued_in_use_bm, scsi_debug_max_queue);
-       tsf = 0;
        inject = 0;
-       if ((qdepth > 0) && (num_in_q >= qdepth))
-               tsf = 1;
-       else if ((scsi_debug_every_nth != 0) &&
-                (SCSI_DEBUG_OPT_RARE_TSF & scsi_debug_opts)) {
+       if ((qdepth > 0) && (num_in_q >= qdepth)) {
+               if (scsi_result) {
+                       spin_unlock_irqrestore(&queued_arr_lock, iflags);
+                       goto respond_in_thread;
+               } else
+                       scsi_result = device_qfull_result;
+       } else if ((scsi_debug_every_nth != 0) &&
+                  (SCSI_DEBUG_OPT_RARE_TSF & scsi_debug_opts) &&
+                  (scsi_result == 0)) {
                if ((num_in_q == (qdepth - 1)) &&
                    (atomic_inc_return(&sdebug_a_tsf) >=
                     abs(scsi_debug_every_nth))) {
                        atomic_set(&sdebug_a_tsf, 0);
                        inject = 1;
-                       tsf = 1;
+                       scsi_result = device_qfull_result;
                }
        }
 
-       /* if (tsf) simulate device reporting SCSI status of TASK SET FULL.
-        * Might override existing CHECK CONDITION. */
-       if (tsf)
-               scsi_result = device_qfull_result;
+       k = find_first_zero_bit(queued_in_use_bm, scsi_debug_max_queue);
        if (k >= scsi_debug_max_queue) {
-               if (SCSI_DEBUG_OPT_ALL_TSF & scsi_debug_opts)
-                       tsf = 1;
                spin_unlock_irqrestore(&queued_arr_lock, iflags);
+               if (scsi_result)
+                       goto respond_in_thread;
+               else if (SCSI_DEBUG_OPT_ALL_TSF & scsi_debug_opts)
+                       scsi_result = device_qfull_result;
                if (SCSI_DEBUG_OPT_Q_NOISE & scsi_debug_opts)
                        sdev_printk(KERN_INFO, sdp,
-                                   "%s: num_in_q=%d, bypass q, %s%s\n",
-                                   __func__, num_in_q,
-                                   (inject ? "<inject> " : ""),
-                                   (tsf ?  "status: TASK SET FULL" :
-                                           "report: host busy"));
-               if (tsf) {
-                       /* queued_arr full so respond in same thread */
-                       cmnd->result = scsi_result;
-                       cmnd->scsi_done(cmnd);
-                       /* As scsi_done() is called "inline" must return 0 */
-                       return 0;
-               } else
+                                   "%s: max_queue=%d exceeded, %s\n",
+                                   __func__, scsi_debug_max_queue,
+                                   (scsi_result ?  "status: TASK SET FULL" :
+                                                   "report: host busy"));
+               if (scsi_result)
+                       goto respond_in_thread;
+               else
                        return SCSI_MLQUEUE_HOST_BUSY;
        }
        __set_bit(k, queued_in_use_bm);
@@ -3117,12 +3110,18 @@ schedule_resp(struct scsi_cmnd *cmnd, struct sdebug_dev_info *devip,
                else
                        tasklet_schedule(sqcp->tletp);
        }
-       if (tsf && (SCSI_DEBUG_OPT_Q_NOISE & scsi_debug_opts))
+       if ((SCSI_DEBUG_OPT_Q_NOISE & scsi_debug_opts) &&
+           (scsi_result == device_qfull_result))
                sdev_printk(KERN_INFO, sdp,
                            "%s: num_in_q=%d +1, %s%s\n", __func__,
                            num_in_q, (inject ? "<inject> " : ""),
                            "status: TASK SET FULL");
        return 0;
+
+respond_in_thread:     /* call back to mid-layer using invocation thread */
+       cmnd->result = scsi_result;
+       cmnd->scsi_done(cmnd);
+       return 0;
 }
 
 /* Note: The following macros create attribute files in the