[PATCH] 1/7 starved changes - use a list_head for starved queue's

Patrick Mansfield
2003-03-25T01:57:56Z

Use a list_head per scsi_host to store a list of scsi request queues
that were "starved" (they were not able to send IO because of per host
limitations).

diff -purN -X /home/patman/dontdiff 25-bk-base/drivers/scsi/hosts.c starve-25/drivers/scsi/hosts.c
--- 25-bk-base/drivers/scsi/hosts.c Thu Mar 6 12:34:47 2003
+++ starve-25/drivers/scsi/hosts.c Mon Mar 24 12:14:28 2003
@@ -383,6 +383,7 @@ struct Scsi_Host * scsi_register(Scsi_Ho
scsi_assign_lock(shost, &shost->default_lock);
INIT_LIST_HEAD(&shost->my_devices);
INIT_LIST_HEAD(&shost->eh_cmd_q);
+ INIT_LIST_HEAD(&shost->starved_list);

init_waitqueue_head(&shost->host_wait);
shost->dma_channel = 0xff;
diff -purN -X /home/patman/dontdiff 25-bk-base/drivers/scsi/hosts.h starve-25/drivers/scsi/hosts.h
--- 25-bk-base/drivers/scsi/hosts.h Tue Mar 18 12:53:33 2003
+++ starve-25/drivers/scsi/hosts.h Mon Mar 24 12:14:28 2003
@@ -380,6 +380,7 @@ struct Scsi_Host
struct scsi_host_cmd_pool *cmd_pool;
spinlock_t free_list_lock;
struct list_head free_list; /* backup store of cmd structs */
+ struct list_head starved_list;

spinlock_t default_lock;
spinlock_t *host_lock;
@@ -471,12 +472,6 @@ struct Scsi_Host
unsigned reverse_ordering:1;

/*
- * Indicates that one or more devices on this host were starved, and
- * when the device becomes less busy that we need to feed them.
- */
- unsigned some_device_starved:1;
-
- /*
* Host has rejected a command because it was busy.
*/
unsigned int host_blocked;
diff -purN -X /home/patman/dontdiff 25-bk-base/drivers/scsi/scsi.h starve-25/drivers/scsi/scsi.h
--- 25-bk-base/drivers/scsi/scsi.h Mon Mar 24 11:57:13 2003
+++ starve-25/drivers/scsi/scsi.h Mon Mar 24 12:14:28 2003
@@ -555,6 +555,7 @@ struct scsi_device {
volatile unsigned short device_busy; /* commands actually active on low-level */
spinlock_t list_lock;
struct list_head cmd_list; /* queue of in use SCSI Command structures */
+ struct list_head starved_entry;
Scsi_Cmnd *current_cmnd; /* currently active command */
unsigned short queue_depth; /* How deep of a queue we want */
unsigned short last_queue_full_depth; /* These two are used by */
@@ -615,8 +616,6 @@ struct scsi_device {
* because we did a bus reset. */
unsigned ten:1; /* support ten byte read / write */
unsigned remap:1; /* support remapping */
- unsigned starved:1; /* unable to process commands because
- host busy */
// unsigned sync:1; /* Sync transfer state, managed by host */
// unsigned wide:1; /* WIDE transfer state, managed by host */

diff -purN -X /home/patman/dontdiff 25-bk-base/drivers/scsi/scsi_lib.c starve-25/drivers/scsi/scsi_lib.c
--- 25-bk-base/drivers/scsi/scsi_lib.c Tue Mar 18 12:53:33 2003
+++ starve-25/drivers/scsi/scsi_lib.c Mon Mar 24 12:14:28 2003
@@ -356,7 +356,6 @@ static void scsi_queue_next_request(requ
struct scsi_device *sdev, *sdev2;
struct Scsi_Host *shost;
unsigned long flags;
- int all_clear;

ASSERT_LOCK(q->queue_lock, 0);

@@ -383,11 +382,6 @@ static void scsi_queue_next_request(requ
__elv_add_request(q, cmd->request, 0, 0);
}

- /*
- * Just hit the requeue function for the queue.
- */
- __blk_run_queue(q);
-
sdev = q->queuedata;
shost = sdev->host;

@@ -412,31 +406,24 @@ static void scsi_queue_next_request(requ
}
}

- /*
- * Now see whether there are other devices on the bus which
- * might be starved. If so, hit the request function. If we
- * don't find any, then it is safe to reset the flag. If we
- * find any device that it is starved, it isn't safe to reset the
- * flag as the queue function releases the lock and thus some
- * other device might have become starved along the way.
- */
- all_clear = 1;
- if (shost->some_device_starved) {
- list_for_each_entry(sdev, &shost->my_devices, siblings) {
- if (shost->can_queue > 0 &&
- shost->host_busy >= shost->can_queue)
- break;
- if (shost->host_blocked || shost->host_self_blocked)
- break;
- if (sdev->device_blocked || !sdev->starved)
- continue;
- __blk_run_queue(sdev->request_queue);
- all_clear = 0;
- }
-
- if (sdev == NULL && all_clear)
- shost->some_device_starved = 0;
+ while (!list_empty(&shost->starved_list) &&
+ !shost->host_blocked && !shost->host_self_blocked &&
+ !((shost->can_queue > 0) &&
+ (shost->host_busy >= shost->can_queue))) {
+ /*
+ * As long as shost is accepting commands and we have
+ * starved queues, call __blk_run_queue. scsi_request_fn
+ * drops the queue_lock and can add us back to the
+ * starved_list.
+ */
+ sdev2 = list_entry(shost->starved_list.next,
+ struct scsi_device, starved_entry);
+ list_del_init(&sdev2->starved_entry);
+ __blk_run_queue(sdev2->request_queue);
}
+
+ __blk_run_queue(q);
+
spin_unlock_irqrestore(q->queue_lock, flags);
}

@@ -1115,23 +1102,16 @@ static void scsi_request_fn(request_queu
*/
if (sdev->device_blocked)
break;
+
+ if (!list_empty(&sdev->starved_entry))
+ break;
+
if ((shost->can_queue > 0 && shost->host_busy >= shost->can_queue) ||
shost->host_blocked || shost->host_self_blocked) {
- /*
- * If we are unable to process any commands at all for
- * this device, then we consider it to be starved.
- * What this means is that there are no outstanding
- * commands for this device and hence we need a
- * little help getting it started again
- * once the host isn't quite so busy.
- */
- if (sdev->device_busy == 0) {
- sdev->starved = 1;
- shost->some_device_starved = 1;
- }
+ list_add_tail(&sdev->starved_entry,
+ &shost->starved_list);
break;
- } else
- sdev->starved = 0;
+ }

/*
* If we couldn't find a request that could be queued, then we
diff -purN -X /home/patman/dontdiff 25-bk-base/drivers/scsi/scsi_scan.c starve-25/drivers/scsi/scsi_scan.c
--- 25-bk-base/drivers/scsi/scsi_scan.c Mon Mar 24 11:57:13 2003
+++ starve-25/drivers/scsi/scsi_scan.c Mon Mar 24 12:14:28 2003
@@ -400,6 +400,7 @@ static struct scsi_device *scsi_alloc_sd
INIT_LIST_HEAD(&sdev->siblings);
INIT_LIST_HEAD(&sdev->same_target_siblings);
INIT_LIST_HEAD(&sdev->cmd_list);
+ INIT_LIST_HEAD(&sdev->starved_entry);
spin_lock_init(&sdev->list_lock);

/*