5 files changed, 40 insertions, 28 deletions

diff --git a/drivers/message/fusion/mptsas.c b/drivers/message/fusion/mptsas.c
index 711fcb5cec87..d636dbe172a3 100644
--- a/drivers/message/fusion/mptsas.c
+++ b/drivers/message/fusion/mptsas.c
@@ -3763,7 +3763,7 @@ mptsas_send_link_status_event(struct fw_event_work *fw_event)
                                                 printk(MYIOC_s_DEBUG_FMT
                                                 "SDEV OUTSTANDING CMDS"
                                                 "%d\n", ioc->name,
-                                                sdev->device_busy));
+                                                atomic_read(&sdev->device_busy)));
                                 }
 
                         }
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index d0bd7e0ab7a8..1ddf0fb43b59 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -302,9 +302,7 @@ void scsi_device_unbusy(struct scsi_device *sdev)
                 spin_unlock_irqrestore(shost->host_lock, flags);
         }
 
-        spin_lock_irqsave(sdev->request_queue->queue_lock, flags);
-        sdev->device_busy--;
-        spin_unlock_irqrestore(sdev->request_queue->queue_lock, flags);
+        atomic_dec(&sdev->device_busy);
 }
 
 /*
@@ -355,9 +353,9 @@ static void scsi_single_lun_run(struct scsi_device *current_sdev)
 
 static inline int scsi_device_is_busy(struct scsi_device *sdev)
 {
-        if (sdev->device_busy >= sdev->queue_depth || sdev->device_blocked)
+        if (atomic_read(&sdev->device_busy) >= sdev->queue_depth ||
+            sdev->device_blocked)
                 return 1;
-
         return 0;
 }
 
@@ -1204,7 +1202,7 @@ scsi_prep_return(struct request_queue *q, struct request *req, int ret)
                  * queue must be restarted, so we schedule a callback to happen
                  * shortly.
                  */
-                if (sdev->device_busy == 0)
+                if (atomic_read(&sdev->device_busy) == 0)
                         blk_delay_queue(q, SCSI_QUEUE_DELAY);
                 break;
         default:
@@ -1255,26 +1253,33 @@ static void scsi_unprep_fn(struct request_queue *q, struct request *req)
 static inline int scsi_dev_queue_ready(struct request_queue *q,
                                   struct scsi_device *sdev)
 {
-        if (sdev->device_busy == 0 && sdev->device_blocked) {
+        unsigned int busy;
+
+        busy = atomic_inc_return(&sdev->device_busy) - 1;
+        if (sdev->device_blocked) {
+                if (busy)
+                        goto out_dec;
+
                 /*
                  * unblock after device_blocked iterates to zero
                  */
-                if (--sdev->device_blocked == 0) {
-                        SCSI_LOG_MLQUEUE(3,
-                                   sdev_printk(KERN_INFO, sdev,
-                                   "unblocking device at zero depth\n"));
-                } else {
+                if (--sdev->device_blocked != 0) {
                         blk_delay_queue(q, SCSI_QUEUE_DELAY);
-                        return 0;
+                        goto out_dec;
                 }
+                SCSI_LOG_MLQUEUE(3, sdev_printk(KERN_INFO, sdev,
+                                   "unblocking device at zero depth\n"));
         }
-        if (scsi_device_is_busy(sdev))
-                return 0;
+
+        if (busy >= sdev->queue_depth)
+                goto out_dec;
 
         return 1;
+out_dec:
+        atomic_dec(&sdev->device_busy);
+        return 0;
 }
 
-
 /*
  * scsi_target_queue_ready: checks if there we can send commands to target
  * @sdev: scsi device on starget to check.
@@ -1448,7 +1453,7 @@ static void scsi_kill_request(struct request *req, struct request_queue *q)
          * bump busy counts.  To bump the counters, we need to dance
          * with the locks as normal issue path does.
          */
-        sdev->device_busy++;
+        atomic_inc(&sdev->device_busy);
         atomic_inc(&shost->host_busy);
         atomic_inc(&starget->target_busy);
 
@@ -1544,7 +1549,7 @@ static void scsi_request_fn(struct request_queue *q)
                  * accept it.
                  */
                 req = blk_peek_request(q);
-                if (!req || !scsi_dev_queue_ready(q, sdev))
+                if (!req)
                         break;
 
                 if (unlikely(!scsi_device_online(sdev))) {
@@ -1554,13 +1559,14 @@ static void scsi_request_fn(struct request_queue *q)
                         continue;
                 }
 
+                if (!scsi_dev_queue_ready(q, sdev))
+                        break;
 
                 /*
                  * Remove the request from the request list.
                  */
                 if (!(blk_queue_tagged(q) && !blk_queue_start_tag(q, req)))
                         blk_start_request(req);
-                sdev->device_busy++;
 
                 spin_unlock_irq(q->queue_lock);
                 cmd = req->special;
@@ -1630,9 +1636,9 @@ static void scsi_request_fn(struct request_queue *q)
          */
         spin_lock_irq(q->queue_lock);
         blk_requeue_request(q, req);
-        sdev->device_busy--;
+        atomic_dec(&sdev->device_busy);
 out_delay:
-        if (sdev->device_busy == 0 && !scsi_device_blocked(sdev))
+        if (atomic_read(&sdev->device_busy) && !scsi_device_blocked(sdev))
                 blk_delay_queue(q, SCSI_QUEUE_DELAY);
 }
 
@@ -2371,7 +2377,7 @@ scsi_device_quiesce(struct scsi_device *sdev)
                 return err;
 
         scsi_run_queue(sdev->request_queue);
-        while (sdev->device_busy) {
+        while (atomic_read(&sdev->device_busy)) {
                 msleep_interruptible(200);
                 scsi_run_queue(sdev->request_queue);
         }
diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c
index de57b8bca7be..79df9847edef 100644
--- a/drivers/scsi/scsi_sysfs.c
+++ b/drivers/scsi/scsi_sysfs.c
@@ -585,13 +585,21 @@ static int scsi_sdev_check_buf_bit(const char *buf)
  * Create the actual show/store functions and data structures.
  */
 sdev_rd_attr (device_blocked, "%d\n");
-sdev_rd_attr (device_busy, "%d\n");
 sdev_rd_attr (type, "%d\n");
 sdev_rd_attr (scsi_level, "%d\n");
 sdev_rd_attr (vendor, "%.8s\n");
 sdev_rd_attr (model, "%.16s\n");
 sdev_rd_attr (rev, "%.4s\n");
 
+static ssize_t
+sdev_show_device_busy(struct device *dev, struct device_attribute *attr,
+                char *buf)
+{
+        struct scsi_device *sdev = to_scsi_device(dev);
+        return snprintf(buf, 20, "%d\n", atomic_read(&sdev->device_busy));
+}
+static DEVICE_ATTR(device_busy, S_IRUGO, sdev_show_device_busy, NULL);
+
 /*
  * TODO: can we make these symlinks to the block layer ones?
  */
diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c
index 7a291f5c7227..01cf88888797 100644
--- a/drivers/scsi/sg.c
+++ b/drivers/scsi/sg.c
@@ -2574,7 +2574,7 @@ static int sg_proc_seq_show_dev(struct seq_file *s, void *v)
                               scsidp->id, scsidp->lun, (int) scsidp->type,
                               1,
                               (int) scsidp->queue_depth,
-                              (int) scsidp->device_busy,
+                              (int) atomic_read(&scsidp->device_busy),
                               (int) scsi_device_online(scsidp));
         }
         read_unlock_irqrestore(&sg_index_lock, iflags);
diff --git a/include/scsi/scsi_device.h b/include/scsi/scsi_device.h
index 4e078b63a9e5..3329901c7243 100644
--- a/include/scsi/scsi_device.h
+++ b/include/scsi/scsi_device.h
@@ -81,9 +81,7 @@ struct scsi_device {
         struct list_head    siblings;   /* list of all devices on this host */
         struct list_head    same_target_siblings; /* just the devices sharing same target id */
 
-        /* this is now protected by the request_queue->queue_lock */
-        unsigned int device_busy;       /* commands actually active on
-                                         * low-level. protected by queue_lock. */
+        atomic_t device_busy;           /* commands actually active on LLDD */
         spinlock_t list_lock;
         struct list_head cmd_list;      /* queue of in use SCSI Command structures */
         struct list_head starved_entry;