diff --git a/drivers/scsi/scsi.c b/drivers/scsi/scsi.c
index 2ac3cb2b9081..f8b79d401d58 100644
--- a/drivers/scsi/scsi.c
+++ b/drivers/scsi/scsi.c
@@ -754,8 +754,12 @@ int scsi_dispatch_cmd(struct scsi_cmnd *cmd)
}
spin_unlock_irqrestore(host->host_lock, flags);
if (rtn) {
- scsi_queue_insert(cmd, (rtn == SCSI_MLQUEUE_DEVICE_BUSY) ?
- rtn : SCSI_MLQUEUE_HOST_BUSY);
+ if (rtn != SCSI_MLQUEUE_DEVICE_BUSY &&
+ rtn != SCSI_MLQUEUE_TARGET_BUSY)
+ rtn = SCSI_MLQUEUE_HOST_BUSY;
+
+ scsi_queue_insert(cmd, rtn);
+
SCSI_LOG_MLQUEUE(3,
printk("queuecommand : request rejected\n"));
}
@@ -800,6 +804,7 @@ static struct scsi_driver *scsi_cmd_to_driver(struct scsi_cmnd *cmd)
void scsi_finish_command(struct scsi_cmnd *cmd)
{
struct scsi_device *sdev = cmd->device;
+ struct scsi_target *starget = scsi_target(sdev);
struct Scsi_Host *shost = sdev->host;
struct scsi_driver *drv;
unsigned int good_bytes;
@@ -815,6 +820,7 @@ void scsi_finish_command(struct scsi_cmnd *cmd)
* XXX(hch): What about locking?
*/
shost->host_blocked = 0;
+ starget->target_blocked = 0;
sdev->device_blocked = 0;
/*
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 98ee55ced592..91c74c55aa5e 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -114,6 +114,7 @@ int scsi_queue_insert(struct scsi_cmnd *cmd, int reason)
{
struct Scsi_Host *host = cmd->device->host;
struct scsi_device *device = cmd->device;
+ struct scsi_target *starget = scsi_target(device);
struct request_queue *q = device->request_queue;
unsigned long flags;
@@ -133,10 +134,17 @@ int scsi_queue_insert(struct scsi_cmnd *cmd, int reason)
* if a command is requeued with no other commands outstanding
* either for the device or for the host.
*/
- if (reason == SCSI_MLQUEUE_HOST_BUSY)
+ switch (reason) {
+ case SCSI_MLQUEUE_HOST_BUSY:
host->host_blocked = host->max_host_blocked;
- else if (reason == SCSI_MLQUEUE_DEVICE_BUSY)
+ break;
+ case SCSI_MLQUEUE_DEVICE_BUSY:
device->device_blocked = device->max_device_blocked;
+ break;
+ case SCSI_MLQUEUE_TARGET_BUSY:
+ starget->target_blocked = starget->max_target_blocked;
+ break;
+ }
/*
* Decrement the counters, since these commands are no longer
@@ -460,10 +468,12 @@ static void scsi_init_cmd_errh(struct scsi_cmnd *cmd)
void scsi_device_unbusy(struct scsi_device *sdev)
{
struct Scsi_Host *shost = sdev->host;
+ struct scsi_target *starget = scsi_target(sdev);
unsigned long flags;
spin_lock_irqsave(shost->host_lock, flags);
shost->host_busy--;
+ starget->target_busy--;
if (unlikely(scsi_host_in_recovery(shost) &&
(shost->host_failed || shost->host_eh_scheduled)))
scsi_eh_wakeup(shost);
@@ -519,6 +529,13 @@ static void scsi_single_lun_run(struct scsi_device *current_sdev)
spin_unlock_irqrestore(shost->host_lock, flags);
}
+static inline int scsi_target_is_busy(struct scsi_target *starget)
+{
+ return ((starget->can_queue > 0 &&
+ starget->target_busy >= starget->can_queue) ||
+ starget->target_blocked);
+}
+
/*
* Function: scsi_run_queue()
*
@@ -533,7 +550,7 @@ static void scsi_single_lun_run(struct scsi_device *current_sdev)
*/
static void scsi_run_queue(struct request_queue *q)
{
- struct scsi_device *sdev = q->queuedata;
+ struct scsi_device *starved_head = NULL, *sdev = q->queuedata;
struct Scsi_Host *shost = sdev->host;
unsigned long flags;
@@ -560,6 +577,21 @@ static void scsi_run_queue(struct request_queue *q)
*/
sdev = list_entry(shost->starved_list.next,
struct scsi_device, starved_entry);
+ /*
+ * The *queue_ready functions can add a device back onto the
+ * starved list's tail, so we must check for a infinite loop.
+ */
+ if (sdev == starved_head)
+ break;
+ if (!starved_head)
+ starved_head = sdev;
+
+ if (scsi_target_is_busy(scsi_target(sdev))) {
+ list_move_tail(&sdev->starved_entry,
+ &shost->starved_list);
+ continue;
+ }
+
list_del_init(&sdev->starved_entry);
spin_unlock(shost->host_lock);
@@ -575,13 +607,6 @@ static void scsi_run_queue(struct request_queue *q)
spin_unlock(sdev->request_queue->queue_lock);
spin_lock(shost->host_lock);
- if (unlikely(!list_empty(&sdev->starved_entry)))
- /*
- * sdev lost a race, and was put back on the
- * starved list. This is unlikely but without this
- * in theory we could loop forever.
- */
- break;
}
spin_unlock_irqrestore(shost->host_lock, flags);
@@ -1344,6 +1369,52 @@ static inline int scsi_dev_queue_ready(struct request_queue *q,
return 1;
}
+
+/*
+ * scsi_target_queue_ready: checks if there we can send commands to target
+ * @sdev: scsi device on starget to check.
+ *
+ * Called with the host lock held.
+ */
+static inline int scsi_target_queue_ready(struct Scsi_Host *shost,
+ struct scsi_device *sdev)
+{
+ struct scsi_target *starget = scsi_target(sdev);
+
+ if (starget->single_lun) {
+ if (starget->starget_sdev_user &&
+ starget->starget_sdev_user != sdev)
+ return 0;
+ starget->starget_sdev_user = sdev;
+ }
+
+ if (starget->target_busy == 0 && starget->target_blocked) {
+ /*
+ * unblock after target_blocked iterates to zero
+ */
+ if (--starget->target_blocked == 0) {
+ SCSI_LOG_MLQUEUE(3, starget_printk(KERN_INFO, starget,
+ "unblocking target at zero depth\n"));
+ } else {
+ blk_plug_device(sdev->request_queue);
+ return 0;
+ }
+ }
+
+ if (scsi_target_is_busy(starget)) {
+ if (list_empty(&sdev->starved_entry)) {
+ list_add_tail(&sdev->starved_entry,
+ &shost->starved_list);
+ return 0;
+ }
+ }
+
+ /* We're OK to process the command, so we can't be starved */
+ if (!list_empty(&sdev->starved_entry))
+ list_del_init(&sdev->starved_entry);
+ return 1;
+}
+
/*
* scsi_host_queue_ready: if we can send requests to shost, return 1 else
* return 0. We must end up running the queue again whenever 0 is
@@ -1390,6 +1461,7 @@ static void scsi_kill_request(struct request *req, struct request_queue *q)
{
struct scsi_cmnd *cmd = req->special;
struct scsi_device *sdev = cmd->device;
+ struct scsi_target *starget = scsi_target(sdev);
struct Scsi_Host *shost = sdev->host;
blkdev_dequeue_request(req);
@@ -1413,6 +1485,7 @@ static void scsi_kill_request(struct request *req, struct request_queue *q)
spin_unlock(sdev->request_queue->queue_lock);
spin_lock(shost->host_lock);
shost->host_busy++;
+ starget->target_busy++;
spin_unlock(shost->host_lock);
spin_lock(sdev->request_queue->queue_lock);
@@ -1550,14 +1623,13 @@ static void scsi_request_fn(struct request_queue *q)
goto not_ready;
}
+ if (!scsi_target_queue_ready(shost, sdev))
+ goto not_ready;
+
if (!scsi_host_queue_ready(q, shost, sdev))
goto not_ready;
- if (scsi_target(sdev)->single_lun) {
- if (scsi_target(sdev)->starget_sdev_user &&
- scsi_target(sdev)->starget_sdev_user != sdev)
- goto not_ready;
- scsi_target(sdev)->starget_sdev_user = sdev;
- }
+
+ scsi_target(sdev)->target_busy++;
shost->host_busy++;
/*
diff --git a/drivers/scsi/scsi_scan.c b/drivers/scsi/scsi_scan.c
index 334862e26a1b..b14dc02c3ded 100644
--- a/drivers/scsi/scsi_scan.c
+++ b/drivers/scsi/scsi_scan.c
@@ -419,6 +419,7 @@ static struct scsi_target *scsi_alloc_target(struct device *parent,
dev->type = &scsi_target_type;
starget->id = id;
starget->channel = channel;
+ starget->can_queue = 0;
INIT_LIST_HEAD(&starget->siblings);
INIT_LIST_HEAD(&starget->devices);
starget->state = STARGET_CREATED;
diff --git a/include/scsi/scsi.h b/include/scsi/scsi.h
index 192f8716aa9e..3a5662b2817e 100644
--- a/include/scsi/scsi.h
+++ b/include/scsi/scsi.h
@@ -426,6 +426,7 @@ static inline int scsi_is_wlun(unsigned int lun)
#define SCSI_MLQUEUE_HOST_BUSY 0x1055
#define SCSI_MLQUEUE_DEVICE_BUSY 0x1056
#define SCSI_MLQUEUE_EH_RETRY 0x1057
+#define SCSI_MLQUEUE_TARGET_BUSY 0x1058
/*
* Use these to separate status msg and our bytes
diff --git a/include/scsi/scsi_device.h b/include/scsi/scsi_device.h
index b49e725be039..a37a8148a310 100644
--- a/include/scsi/scsi_device.h
+++ b/include/scsi/scsi_device.h
@@ -238,6 +238,16 @@ struct scsi_target {
* for the device at a time. */
unsigned int pdt_1f_for_no_lun; /* PDT = 0x1f */
/* means no lun present */
+ /* commands actually active on LLD. protected by host lock. */
+ unsigned int target_busy;
+ /*
+ * LLDs should set this in the slave_alloc host template callout.
+ * If set to zero then there is not limit.
+ */
+ unsigned int can_queue;
+ unsigned int target_blocked;
+ unsigned int max_target_blocked;
+#define SCSI_DEFAULT_TARGET_BLOCKED 3
char scsi_level;
struct execute_work ew;