[SCSI] gdth: !use_sg cleanup and use of scsi accessors

gdth_execute() will issue an internal, none scsi-standard commands
onto __gdth_queuecommand(). Since it is not recommended to set
struct scsi_cmnd IO members in llds, gdth now uses internal IO
members for IO. In the case of gdth_execute() these members will be
set properly. In case the command was issued from scsi-ml
(by gdth_queuecommand) they will be set from scsi IO accessors.

  * define gdth IO accessors and use them throughout the driver.
  * use an sg-of-one in gdth_execute() and fix gdth_special_cmd()
    accordingly.
  * Clean the not use_sg code path and company

Signed-off-by Boaz Harrosh <bharrosh@panasas.com>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>

2 files changed, 109 insertions, 126 deletions

diff --git a/drivers/scsi/gdth.c b/drivers/scsi/gdth.c
index a68004b0d90b..0153d1d8b12e 100644
--- a/drivers/scsi/gdth.c
+++ b/drivers/scsi/gdth.c
@@ -85,11 +85,11 @@
 
 /* The meaning of the Scsi_Pointer members in this driver is as follows:
  * ptr:                     Chaining
- * this_residual:           unused
- * buffer:                  unused
- * dma_handle:              will drop in !use_sg patch.
- * buffers_residual:        unused
- * Status:                  DMA mem. mappings (FIXME: drop in !use_sg patch.)
+ * this_residual:           gdth_bufflen
+ * buffer:                  gdth_sglist
+ * dma_handle:              unused
+ * buffers_residual:        gdth_sg_count
+ * Status:                  unused
  * Message:                 unused
  * have_data_in:            unused
  * sent_command:            unused
@@ -132,6 +132,7 @@
 #include <asm/uaccess.h>
 #include <linux/spinlock.h>
 #include <linux/blkdev.h>
+#include <linux/scatterlist.h>
 
 #include "scsi.h"
 #include <scsi/scsi_host.h>
@@ -159,7 +160,7 @@ static void gdth_readapp_event(gdth_ha_str *ha, unchar application,
 static void gdth_clear_events(void);
 
 static void gdth_copy_internal_data(gdth_ha_str *ha, Scsi_Cmnd *scp,
-                                    char *buffer,ushort count);
+                                    char *buffer, ushort count, int to_buffer);
 static int gdth_internal_cache_cmd(gdth_ha_str *ha, Scsi_Cmnd *scp);
 static int gdth_fill_cache_cmd(gdth_ha_str *ha, Scsi_Cmnd *scp, ushort hdrive);
 
@@ -373,6 +374,47 @@ static const struct file_operations gdth_fops = {
     .release = gdth_close,
 };
 
+/*
+ * gdth scsi_command access wrappers.
+ *   below 6 functions are used throughout the driver to access scsi_command's
+ *   io parameters. The reason we do not use the regular accessors from
+ *   scsi_cmnd.h is because of gdth_execute(). Since it is unrecommended for
+ *   llds to directly set scsi_cmnd's IO members. This driver will use SCp
+ *   members for IO parameters, and will copy scsi_cmnd's members to Scp
+ *   members in queuecommand. For internal commands through gdth_execute()
+ *   SCp's members will be set directly.
+ */
+static inline unsigned gdth_bufflen(struct scsi_cmnd *cmd)
+{
+        return (unsigned)cmd->SCp.this_residual;
+}
+
+static inline void gdth_set_bufflen(struct scsi_cmnd *cmd, unsigned bufflen)
+{
+        cmd->SCp.this_residual = bufflen;
+}
+
+static inline unsigned gdth_sg_count(struct scsi_cmnd *cmd)
+{
+        return (unsigned)cmd->SCp.buffers_residual;
+}
+
+static inline void gdth_set_sg_count(struct scsi_cmnd *cmd, unsigned sg_count)
+{
+        cmd->SCp.buffers_residual = sg_count;
+}
+
+static inline struct scatterlist *gdth_sglist(struct scsi_cmnd *cmd)
+{
+        return cmd->SCp.buffer;
+}
+
+static inline void gdth_set_sglist(struct scsi_cmnd *cmd,
+                                   struct scatterlist *sglist)
+{
+        cmd->SCp.buffer = sglist;
+}
+
 #include "gdth_proc.h"
 #include "gdth_proc.c"
 
@@ -452,6 +494,7 @@ int __gdth_execute(struct scsi_device *sdev, gdth_cmd_str *gdtcmd, char *cmnd,
     gdth_ha_str *ha = shost_priv(sdev->host);
     Scsi_Cmnd *scp;
     struct gdth_cmndinfo cmndinfo;
+    struct scatterlist one_sg;
     DECLARE_COMPLETION_ONSTACK(wait);
     int rval;
 
@@ -465,7 +508,10 @@ int __gdth_execute(struct scsi_device *sdev, gdth_cmd_str *gdtcmd, char *cmnd,
     /* use request field to save the ptr. to completion struct. */
     scp->request = (struct request *)&wait;
     scp->timeout_per_command = timeout*HZ;
-    scp->request_buffer = gdtcmd;
+    sg_init_one(&one_sg, gdtcmd, sizeof(*gdtcmd));
+    gdth_set_sglist(scp, &one_sg);
+    gdth_set_sg_count(scp, 1);
+    gdth_set_bufflen(scp, sizeof(*gdtcmd));
     scp->cmd_len = 12;
     memcpy(scp->cmnd, cmnd, 12);
     cmndinfo.priority = IOCTL_PRI;
@@ -2303,24 +2349,28 @@ static void gdth_next(gdth_ha_str *ha)
                    ha->hanum, cmd_index);
     }
 }
-   
+
+/*
+ * gdth_copy_internal_data() - copy to/from a buffer onto a scsi_cmnd's
+ * buffers, kmap_atomic() as needed.
+ */
 static void gdth_copy_internal_data(gdth_ha_str *ha, Scsi_Cmnd *scp,
-                                    char *buffer,ushort count)
+                                    char *buffer, ushort count, int to_buffer)
 {
-    ushort cpcount,i;
+    ushort cpcount,i, max_sg = gdth_sg_count(scp);
     ushort cpsum,cpnow;
     struct scatterlist *sl;
     char *address;
 
-    cpcount = count<=(ushort)scp->request_bufflen ? count:(ushort)scp->request_bufflen;
+    cpcount = min_t(ushort, count, gdth_bufflen(scp));
 
-    if (scp->use_sg) {
-        sl = (struct scatterlist *)scp->request_buffer;
-        for (i=0,cpsum=0; i<scp->use_sg; ++i,++sl) {
+    if (cpcount) {
+        cpsum=0;
+        scsi_for_each_sg(scp, sl, max_sg, i) {
             unsigned long flags;
             cpnow = (ushort)sl->length;
             TRACE(("copy_internal() now %d sum %d count %d %d\n",
-                          cpnow,cpsum,cpcount,(ushort)scp->bufflen));
+                          cpnow, cpsum, cpcount, gdth_bufflen(scp)));
             if (cpsum+cpnow > cpcount) 
                 cpnow = cpcount - cpsum;
             cpsum += cpnow;
@@ -2331,7 +2381,10 @@ static void gdth_copy_internal_data(gdth_ha_str *ha, Scsi_Cmnd *scp,
             }
             local_irq_save(flags);
             address = kmap_atomic(sl->page, KM_BIO_SRC_IRQ) + sl->offset;
-            memcpy(address,buffer,cpnow);
+            if (to_buffer)
+                memcpy(buffer, address, cpnow);
+            else
+                memcpy(address, buffer, cpnow);
             flush_dcache_page(sl->page);
             kunmap_atomic(address, KM_BIO_SRC_IRQ);
             local_irq_restore(flags);
@@ -2339,9 +2392,10 @@ static void gdth_copy_internal_data(gdth_ha_str *ha, Scsi_Cmnd *scp,
                 break;
             buffer += cpnow;
         }
-    } else {
-        TRACE(("copy_internal() count %d\n",cpcount));
-        memcpy((char*)scp->request_buffer,buffer,cpcount);
+    } else if (count) {
+        printk("GDT-HA %d: SCSI command with no buffers but data transfer expected!\n",
+               ha->hanum);
+        WARN_ON(1);
     }
 }
 
@@ -2384,7 +2438,7 @@ static int gdth_internal_cache_cmd(gdth_ha_str *ha, Scsi_Cmnd *scp)
         strcpy(inq.vendor,ha->oem_name);