[SCSI] fix up request buffer reference in various scsi drivers

Various scsi drivers use scsi_cmnd.buffer and scsi_cmnd.bufflen in their
queuecommand functions.  Those fields are internal storage for the
midlayer only and are used to restore the original payload after
request_buffer and request_bufflen have been overwritten for EH.  Using
the buffer and bufflen fields means they do very broken things in error
handling.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>
diff --git a/drivers/scsi/3w-xxxx.c b/drivers/scsi/3w-xxxx.c
index e8e41e6..37a58c6 100644
--- a/drivers/scsi/3w-xxxx.c
+++ b/drivers/scsi/3w-xxxx.c
@@ -1286,7 +1286,7 @@
 	if (cmd->use_sg == 0)
 		return 0;
 
-	use_sg = pci_map_sg(pdev, cmd->buffer, cmd->use_sg, DMA_BIDIRECTIONAL);
+	use_sg = pci_map_sg(pdev, cmd->request_buffer, cmd->use_sg, DMA_BIDIRECTIONAL);
 	
 	if (use_sg == 0) {
 		printk(KERN_WARNING "3w-xxxx: tw_map_scsi_sg_data(): pci_map_sg() failed.\n");