[SCSI] use scatter lists for all block pc requests and simplify hw handlers

Here's the proof of concept for this one.  It converts scsi_wait_req to
do correct REQ_BLOCK_PC submission (and works nicely in my setup).

The final goal should be to eliminate struct scsi_request, but that
can't be done until the character submission paths of sg and st are also
modified.

There's some loss of functionality to this: retries are no longer
controllable (except by setting REQ_FASTFAIL) and the wait_req API needs
to be altered, but it looks very nice.

Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>

1 files changed, 59 insertions, 37 deletions

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 7a91ca3d32a6..253c1a98d159 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -232,23 +232,6 @@ void scsi_do_req(struct scsi_request *sreq, const void *cmnd,
 }
 EXPORT_SYMBOL(scsi_do_req);
 
-static void scsi_wait_done(struct scsi_cmnd *cmd)
-{
-        struct request *req = cmd->request;
-        struct request_queue *q = cmd->device->request_queue;
-        unsigned long flags;
-
-        req->rq_status = RQ_SCSI_DONE;  /* Busy, but indicate request done */
-
-        spin_lock_irqsave(q->queue_lock, flags);
-        if (blk_rq_tagged(req))
-                blk_queue_end_tag(q, req);
-        spin_unlock_irqrestore(q->queue_lock, flags);
-
-        if (req->waiting)
-                complete(req->waiting);
-}
-
 /* This is the end routine we get to if a command was never attached
  * to the request.  Simply complete the request without changing
  * rq_status; this will cause a DRIVER_ERROR. */
@@ -263,19 +246,36 @@ void scsi_wait_req(struct scsi_request *sreq, const void *cmnd, void *buffer,
                    unsigned bufflen, int timeout, int retries)
 {
         DECLARE_COMPLETION(wait);
-        
-        sreq->sr_request->waiting = &wait;
-        sreq->sr_request->rq_status = RQ_SCSI_BUSY;
-        sreq->sr_request->end_io = scsi_wait_req_end_io;
-        scsi_do_req(sreq, cmnd, buffer, bufflen, scsi_wait_done,
-                        timeout, retries);
+        struct request *req;
+
+        if (bufflen)
+                req = blk_rq_map_kern(sreq->sr_device->request_queue,
+                                      sreq->sr_data_direction == DMA_TO_DEVICE,
+                                      buffer, bufflen, __GFP_WAIT);
+        else
+                req = blk_get_request(sreq->sr_device->request_queue, READ,
+                                      __GFP_WAIT);
+        req->flags |= REQ_NOMERGE;
+        req->waiting = &wait;
+        req->end_io = scsi_wait_req_end_io;
+        req->cmd_len = COMMAND_SIZE(((u8 *)cmnd)[0]);
+        req->sense = sreq->sr_sense_buffer;
+        req->sense_len = 0;
+        memcpy(req->cmd, cmnd, req->cmd_len);
+        req->timeout = timeout;
+        req->flags |= REQ_BLOCK_PC;
+        req->rq_disk = NULL;
+        blk_insert_request(sreq->sr_device->request_queue, req,
+                           sreq->sr_data_direction == DMA_TO_DEVICE, NULL);
         wait_for_completion(&wait);
         sreq->sr_request->waiting = NULL;
-        if (sreq->sr_request->rq_status != RQ_SCSI_DONE)
+        sreq->sr_result = req->errors;
+        if (req->errors)
                 sreq->sr_result |= (DRIVER_ERROR << 24);
 
-        __scsi_release_request(sreq);
+        blk_put_request(req);
 }
+
 EXPORT_SYMBOL(scsi_wait_req);
 
 /*
@@ -878,11 +878,12 @@ void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes,
                 return;
         }
         if (result) {
-                printk(KERN_INFO "SCSI error : <%d %d %d %d> return code "
-                       "= 0x%x\n", cmd->device->host->host_no,
-                       cmd->device->channel,
-                       cmd->device->id,
-                       cmd->device->lun, result);
+                if (!(req->flags & REQ_SPECIAL))
+                        printk(KERN_INFO "SCSI error : <%d %d %d %d> return code "
+                               "= 0x%x\n", cmd->device->host->host_no,
+                               cmd->device->channel,
+                               cmd->device->id,
+                               cmd->device->lun, result);
 
                 if (driver_byte(result) & DRIVER_SENSE)
                         scsi_print_sense("", cmd);
@@ -1020,6 +1021,12 @@ static int scsi_issue_flush_fn(request_queue_t *q, struct gendisk *disk,
         return -EOPNOTSUPP;
 }
 
+static void scsi_generic_done(struct scsi_cmnd *cmd)
+{
+        BUG_ON(!blk_pc_request(cmd->request));
+        scsi_io_completion(cmd, cmd->result == 0 ? cmd->bufflen : 0, 0);
+}
+
 static int scsi_prep_fn(struct request_queue *q, struct request *req)
 {
         struct scsi_device *sdev = q->queuedata;
@@ -1061,7 +1068,7 @@ static int scsi_prep_fn(struct request_queue *q, struct request *req)
          * these two cases differently.  We differentiate by looking
          * at request->cmd, as this tells us the real story.
          */
-        if (req->flags & REQ_SPECIAL) {
+        if (req->flags & REQ_SPECIAL && req->special) {
                 struct scsi_request *sreq = req->special;
 
                 if (sreq->sr_magic == SCSI_REQ_MAGIC) {
@@ -1073,7 +1080,7 @@ static int scsi_prep_fn(struct request_queue *q, struct request *req)
                         cmd = req->special;
         } else if (req->flags & (REQ_CMD | REQ_BLOCK_PC)) {
 
-                if(unlikely(specials_only)) {
+                if(unlikely(specials_only) && !(req->flags & REQ_SPECIAL)) {
                         if(specials_only == SDEV_QUIESCE ||
                                         specials_only == SDEV_BLOCK)
                                 return BLKPREP_DEFER;
@@ -1142,11 +1149,26 @@ static int scsi_prep_fn(struct request_queue *q, struct request *req)
                 /*
                  * Initialize the actual SCSI command for this request.
                  */
-                drv = *(struct scsi_driver **)req->rq_disk->private_data;
-                if (unlikely(!drv->init_command(cmd))) {
-                        scsi_release_buffers(cmd);
-                        scsi_put_command(cmd);
-                        return BLKPREP_KILL;
+                if (req->rq_disk) {
+                        drv = *(struct scsi_driver **)req->rq_disk->private_data;
+                        if (unlikely(!drv->init_command(cmd))) {
+                                scsi_release_buffers(cmd);
+                                scsi_put_command(cmd);
+                                return BLKPREP_KILL;
+                        }
+                } else {
+                        memcpy(cmd->cmnd, req->cmd, sizeof(cmd->cmnd));
+                        if (rq_data_dir(req) == WRITE)
+                                cmd->sc_data_direction = DMA_TO_DEVICE;
+                        else if (req->data_len)
+                                cmd->sc_data_direction = DMA_FROM_DEVICE;
+                        else
+                                cmd->sc_data_direction = DMA_NONE;
+                        
+                        cmd->transfersize = req->data_len;
+                        cmd->allowed = 3;
+                        cmd->timeout_per_command = req->timeout;
+                        cmd->done = scsi_generic_done;
                 }
         }