SCSI host lock push-down

Move the mid-layer's ->queuecommand() invocation from being locked
with the host lock to being unlocked to facilitate speeding up the
critical path for drivers who don't need this lock taken anyway.

The patch below presents a simple SCSI host lock push-down as an
equivalent transformation.  No locking or other behavior should change
with this patch.  All existing bugs and locking orders are preserved.

Additionally, add one parameter to queuecommand,
	struct Scsi_Host *
and remove one parameter from queuecommand,
	void (*done)(struct scsi_cmnd *)

Scsi_Host* is a convenient pointer that most host drivers need anyway,
and 'done' is redundant to struct scsi_cmnd->scsi_done.

Minimal code disturbance was attempted with this change.  Most drivers
needed only two one-line modifications for their host lock push-down.

Signed-off-by: Jeff Garzik <jgarzik@redhat.com>
Acked-by: James Bottomley <James.Bottomley@suse.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 4 insertions, 3 deletions

diff --git a/drivers/scsi/arcmsr/arcmsr_hba.c b/drivers/scsi/arcmsr/arcmsr_hba.c
index 05a78e515a24..17e3df4f016f 100644
--- a/drivers/scsi/arcmsr/arcmsr_hba.c
+++ b/drivers/scsi/arcmsr/arcmsr_hba.c
@@ -85,8 +85,7 @@ static int arcmsr_abort(struct scsi_cmnd *);
 static int arcmsr_bus_reset(struct scsi_cmnd *);
 static int arcmsr_bios_param(struct scsi_device *sdev,
                 struct block_device *bdev, sector_t capacity, int *info);
-static int arcmsr_queue_command(struct scsi_cmnd *cmd,
-                                        void (*done) (struct scsi_cmnd *));
+static int arcmsr_queue_command(struct Scsi_Host *h, struct scsi_cmnd *cmd);
 static int arcmsr_probe(struct pci_dev *pdev,
                                 const struct pci_device_id *id);
 static void arcmsr_remove(struct pci_dev *pdev);
@@ -2081,7 +2080,7 @@ static void arcmsr_handle_virtual_command(struct AdapterControlBlock *acb,
         }
 }
 
-static int arcmsr_queue_command(struct scsi_cmnd *cmd,
+static int arcmsr_queue_command_lck(struct scsi_cmnd *cmd,
         void (* done)(struct scsi_cmnd *))
 {
         struct Scsi_Host *host = cmd->device->host;
@@ -2124,6 +2123,8 @@ static int arcmsr_queue_command(struct scsi_cmnd *cmd,
         return 0;
 }
 
+static DEF_SCSI_QCMD(arcmsr_queue_command)
+
 static bool arcmsr_get_hba_config(struct AdapterControlBlock *acb)
 {
         struct MessageUnit_A __iomem *reg = acb->pmuA;