02_scsi_REQ_SPECIAL_semantic_scsi_queue_insert.patch
scsi_queue_insert() used to use blk_insert_request() for
requeueing requests. This behavior depends on the unobvious
behavior of blk_insert_request() setting REQ_SPECIAL and
REQ_SOFTBARRIER when requeueing. This patch makes
scsi_queue_insert() use blk_requeue_request() and explicitly
set REQ_SOFTBARRIER. As REQ_SPECIAL now means special
requests, the flag is not set on requeue.
Note that scsi_queue_insert() now calls scsi_run_queue()
itself, and the prototype of the function is added right above
scsi_queue_insert(). This is temporary, as later requeue path
consolidation patchset removes scsi_queue_insert(). By adding
temporary prototype, we can do away with unnecessary changes.
Signed-off-by: Tejun Heo <htejun@xxxxxxxxx>
scsi_lib.c | 24 ++++++++++++++----------
1 files changed, 14 insertions(+), 10 deletions(-)
Index: scsi-reqfn-export/drivers/scsi/scsi_lib.c
===================================================================
--- scsi-reqfn-export.orig/drivers/scsi/scsi_lib.c 2005-04-11 12:27:07.000000000 +0900
+++ scsi-reqfn-export/drivers/scsi/scsi_lib.c 2005-04-11 12:27:07.000000000 +0900
@@ -96,6 +96,8 @@ int scsi_insert_special_req(struct scsi_
return 0;
}
+static void scsi_run_queue(struct request_queue *q);
+
/*
* Function: scsi_queue_insert()
*
@@ -119,6 +121,8 @@ int scsi_queue_insert(struct scsi_cmnd *
{
struct Scsi_Host *host = cmd->device->host;
struct scsi_device *device = cmd->device;
+ struct request_queue *q = device->request_queue;
+ unsigned long flags;
SCSI_LOG_MLQUEUE(1,
printk("Inserting command %p into mlqueue\n", cmd));
@@ -154,17 +158,17 @@ int scsi_queue_insert(struct scsi_cmnd *
scsi_device_unbusy(device);
/*
- * Insert this command at the head of the queue for it's device.
- * It will go before all other commands that are already in the queue.
- *
- * NOTE: there is magic here about the way the queue is plugged if
- * we have no outstanding commands.
- *
- * Although this *doesn't* plug the queue, it does call the request
- * function. The SCSI request function detects the blocked condition
- * and plugs the queue appropriately.
+ * Requeue the command. Turn on REQ_SOFTBARRIER to prevent
+ * other requests from passing this request.
*/
- blk_insert_request(device->request_queue, cmd->request, 1, cmd, 1);
+ cmd->request->flags |= REQ_SOFTBARRIER;
+
+ spin_lock_irqsave(q->queue_lock, flags);
+ blk_requeue_request(q, cmd->request);
+ spin_unlock_irqrestore(q->queue_lock, flags);
+
+ scsi_run_queue(q);
+
return 0;
}
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