michaelc@xxxxxxxxxxx wrote:
+static inline int scsi_target_ready(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->can_queue && starget->target_busy >= starget->can_queue)
+ return 0;
+ 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 (starget->target_blocked)
+ return 0;
Sorry old patch. This one can starve devices here. An updated patch is
attached.
diff --git a/drivers/scsi/scsi.c b/drivers/scsi/scsi.c
index b35d194..339760a 100644
--- a/drivers/scsi/scsi.c
+++ b/drivers/scsi/scsi.c
@@ -628,9 +628,12 @@ int scsi_dispatch_cmd(struct scsi_cmnd *cmd)
if (rtn) {
if (scsi_delete_timer(cmd)) {
atomic_inc(&cmd->device->iodone_cnt);
- 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"));
@@ -729,6 +732,7 @@ 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;
@@ -744,6 +748,7 @@ 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 b12fb31..9590630 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)
- host->host_blocked = host->max_host_blocked;
- else if (reason == SCSI_MLQUEUE_DEVICE_BUSY)
- device->device_blocked = device->max_device_blocked;
+ switch (reason) {
+ case SCSI_MLQUEUE_HOST_BUSY:
+ host->host_blocked = host->max_host_blocked;
+ 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
@@ -452,10 +460,12 @@ 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);
@@ -1296,6 +1306,51 @@ static inline int scsi_dev_queue_ready(struct request_queue *q,
return 1;
}
+
+/*
+ * scsi_target_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_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 ((starget->can_queue > 0 &&
+ starget->target_busy >= starget->can_queue) ||
+ starget->target_blocked) {
+ if (list_empty(&sdev->starved_entry))
+ list_add_tail(&sdev->starved_entry,
+ &shost->starved_list);
+ return 0;
+ }
+
+ 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
@@ -1343,6 +1398,7 @@ 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);
@@ -1366,6 +1422,7 @@ 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);
@@ -1479,14 +1536,13 @@ static void scsi_request_fn(struct request_queue *q)
}
spin_lock(shost->host_lock);
+ if (!scsi_target_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 1dc165a..c9f7b74 100644
--- a/drivers/scsi/scsi_scan.c
+++ b/drivers/scsi/scsi_scan.c
@@ -396,6 +396,7 @@ static struct scsi_target *scsi_alloc_target(struct device *parent,
shost->host_no, channel, id);
starget->id = id;
starget->channel = channel;
+ starget->can_queue = 0;
INIT_LIST_HEAD(&starget->siblings);
INIT_LIST_HEAD(&starget->devices);
starget->state = STARGET_RUNNING;
diff --git a/include/scsi/scsi.h b/include/scsi/scsi.h
index 8225157..d4b23fc 100644
--- a/include/scsi/scsi.h
+++ b/include/scsi/scsi.h
@@ -367,6 +367,7 @@ struct scsi_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 ab7acbe..f8e4184 100644
--- a/include/scsi/scsi_device.h
+++ b/include/scsi/scsi_device.h
@@ -205,6 +205,16 @@ 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;
