8 files changed, 108 insertions, 233 deletions

diff --git a/drivers/scsi/aha152x.c b/drivers/scsi/aha152x.c
index cff3d389b010..f974869ea323 100644
--- a/drivers/scsi/aha152x.c
+++ b/drivers/scsi/aha152x.c
@@ -1179,6 +1179,10 @@ static int aha152x_device_reset(Scsi_Cmnd * SCpnt)
         DECLARE_MUTEX_LOCKED(sem);
         struct timer_list timer;
         int ret, issued, disconnected;
+        unsigned char old_cmd_len = SCpnt->cmd_len;
+        unsigned short old_use_sg = SCpnt->use_sg;
+        void *old_buffer = SCpnt->request_buffer;
+        unsigned old_bufflen = SCpnt->request_bufflen;
         unsigned long flags;
 
 #if defined(AHA152X_DEBUG)
@@ -1212,11 +1216,11 @@ static int aha152x_device_reset(Scsi_Cmnd * SCpnt)
         add_timer(&timer);
         down(&sem);
         del_timer(&timer);
-        
-        SCpnt->cmd_len         = SCpnt->old_cmd_len;
-        SCpnt->use_sg          = SCpnt->old_use_sg;
-        SCpnt->request_buffer  = SCpnt->buffer;
-        SCpnt->request_bufflen = SCpnt->bufflen;
+
+        SCpnt->cmd_len         = old_cmd_len;
+        SCpnt->use_sg          = old_use_sg;
+        SCpnt->request_buffer  = old_buffer;
+        SCpnt->request_bufflen = old_bufflen;
 
         DO_LOCK(flags);
 
diff --git a/drivers/scsi/scsi.c b/drivers/scsi/scsi.c
index 2ab7df0dcfe8..b332caddd5b3 100644
--- a/drivers/scsi/scsi.c
+++ b/drivers/scsi/scsi.c
@@ -346,7 +346,7 @@ void scsi_log_send(struct scsi_cmnd *cmd)
                         if (level > 3) {
                                 printk(KERN_INFO "buffer = 0x%p, bufflen = %d,"
                                        " done = 0x%p, queuecommand 0x%p\n",
-                                        cmd->buffer, cmd->bufflen,
+                                        cmd->request_buffer, cmd->request_bufflen,
                                         cmd->done,
                                         sdev->host->hostt->queuecommand);
 
@@ -661,11 +661,6 @@ void __scsi_done(struct scsi_cmnd *cmd)
  */
 int scsi_retry_command(struct scsi_cmnd *cmd)
 {
-        /*
-         * Restore the SCSI command state.
-         */
-        scsi_setup_cmd_retry(cmd);
-
         /*
          * Zero the sense information from the last time we tried
          * this command.
@@ -711,10 +706,6 @@ void scsi_finish_command(struct scsi_cmnd *cmd)
                                 "Notifying upper driver of completion "
                                 "(result %x)\n", cmd->result));
 
-        /*
-         * We can get here with use_sg=0, causing a panic in the upper level
-         */
-        cmd->use_sg = cmd->old_use_sg;
         cmd->done(cmd);
 }
 EXPORT_SYMBOL(scsi_finish_command);
diff --git a/drivers/scsi/scsi_error.c b/drivers/scsi/scsi_error.c
index 6683d596234a..6a5b731bd5ba 100644
--- a/drivers/scsi/scsi_error.c
+++ b/drivers/scsi/scsi_error.c
@@ -460,19 +460,67 @@ static void scsi_eh_done(struct scsi_cmnd *scmd)
  * Return value:
  *    SUCCESS or FAILED or NEEDS_RETRY
  **/
-static int scsi_send_eh_cmnd(struct scsi_cmnd *scmd, int timeout)
+static int scsi_send_eh_cmnd(struct scsi_cmnd *scmd, int timeout, int copy_sense)
 {
         struct scsi_device *sdev = scmd->device;
         struct Scsi_Host *shost = sdev->host;
+        int old_result = scmd->result;
         DECLARE_COMPLETION(done);
         unsigned long timeleft;
         unsigned long flags;
+        unsigned char old_cmnd[MAX_COMMAND_SIZE];
+        enum dma_data_direction old_data_direction;
+        unsigned short old_use_sg;
+        unsigned char old_cmd_len;
+        unsigned old_bufflen;
+        void *old_buffer;
         int rtn;
 
+        /*
+         * We need saved copies of a number of fields - this is because
+         * error handling may need to overwrite these with different values
+         * to run different commands, and once error handling is complete,
+         * we will need to restore these values prior to running the actual
+         * command.
+         */
+        old_buffer = scmd->request_buffer;
+        old_bufflen = scmd->request_bufflen;
+        memcpy(old_cmnd, scmd->cmnd, sizeof(scmd->cmnd));
+        old_data_direction = scmd->sc_data_direction;
+        old_cmd_len = scmd->cmd_len;
+        old_use_sg = scmd->use_sg;
+
+        if (copy_sense) {
+                int gfp_mask = GFP_ATOMIC;
+
+                if (shost->hostt->unchecked_isa_dma)
+                        gfp_mask |= __GFP_DMA;
+
+                scmd->sc_data_direction = DMA_FROM_DEVICE;
+                scmd->request_bufflen = 252;
+                scmd->request_buffer = kzalloc(scmd->request_bufflen, gfp_mask);
+                if (!scmd->request_buffer)
+                        return FAILED;
+        } else {
+                scmd->request_buffer = NULL;
+                scmd->request_bufflen = 0;
+                scmd->sc_data_direction = DMA_NONE;
+        }
+
+        scmd->underflow = 0;
+        scmd->use_sg = 0;
+        scmd->cmd_len = COMMAND_SIZE(scmd->cmnd[0]);
+
         if (sdev->scsi_level <= SCSI_2)
                 scmd->cmnd[1] = (scmd->cmnd[1] & 0x1f) |
                         (sdev->lun << 5 & 0xe0);
 
+        /*
+         * Zero the sense buffer.  The scsi spec mandates that any
+         * untransferred sense data should be interpreted as being zero.
+         */
+        memset(scmd->sense_buffer, 0, sizeof(scmd->sense_buffer));
+
         shost->eh_action = &done;
 
         spin_lock_irqsave(shost->host_lock, flags);
@@ -522,6 +570,29 @@ static int scsi_send_eh_cmnd(struct scsi_cmnd *scmd, int timeout)
                 rtn = FAILED;
         }
 
+
+        /*
+         * Last chance to have valid sense data.
+         */
+        if (copy_sense) {
+                if (!SCSI_SENSE_VALID(scmd)) {
+                        memcpy(scmd->sense_buffer, scmd->request_buffer,
+                               sizeof(scmd->sense_buffer));
+                }
+                kfree(scmd->request_buffer);
+        }
+
+
+        /*
+         * Restore original data
+         */
+        scmd->request_buffer = old_buffer;
+        scmd->request_bufflen = old_bufflen;
+        memcpy(scmd->cmnd, old_cmnd, sizeof(scmd->cmnd));
+        scmd->sc_data_direction = old_data_direction;
+        scmd->cmd_len = old_cmd_len;
+        scmd->use_sg = old_use_sg;
+        scmd->result = old_result;
         return rtn;
 }
 
@@ -537,56 +608,10 @@ static int scsi_send_eh_cmnd(struct scsi_cmnd *scmd, int timeout)
 static int scsi_request_sense(struct scsi_cmnd *scmd)
 {
         static unsigned char generic_sense[6] =
-        {REQUEST_SENSE, 0, 0, 0, 252, 0};
-        unsigned char *scsi_result;
-        int saved_result;
-        int rtn;
+                {REQUEST_SENSE, 0, 0, 0, 252, 0};
 
         memcpy(scmd->cmnd, generic_sense, sizeof(generic_sense));
-
-        scsi_result = kmalloc(252, GFP_ATOMIC | ((scmd->device->host->hostt->unchecked_isa_dma) ? __GFP_DMA : 0));
-
-
-        if (unlikely(!scsi_result)) {
-                printk(KERN_ERR "%s: cannot allocate scsi_result.\n",
-                       __FUNCTION__);
-                return FAILED;
-        }
-
-        /*
-         * zero the sense buffer.  some host adapters automatically always
-         * request sense, so it is not a good idea that
-         * scmd->request_buffer and scmd->sense_buffer point to the same
-         * address (db).  0 is not a valid sense code. 
-         */
-        memset(scmd->sense_buffer, 0, sizeof(scmd->sense_buffer));
-        memset(scsi_result, 0, 252);
-
-        saved_result = scmd->result;
-        scmd->request_buffer = scsi_result;
-        scmd->request_bufflen = 252;
-        scmd->use_sg = 0;
-        scmd->cmd_len = COMMAND_SIZE(scmd->cmnd[0]);
-        scmd->sc_data_direction = DMA_FROM_DEVICE;
-        scmd->underflow = 0;
-
-        rtn = scsi_send_eh_cmnd(scmd, SENSE_TIMEOUT);
-
-        /* last chance to have valid sense data */
-        if(!SCSI_SENSE_VALID(scmd)) {
-                memcpy(scmd->sense_buffer, scmd->request_buffer,
-                       sizeof(scmd->sense_buffer));
-        }
-
-        kfree(scsi_result);
-
-        /*
-         * when we eventually call scsi_finish, we really wish to complete
-         * the original request, so let's restore the original data. (db)
-         */
-        scsi_setup_cmd_retry(scmd);
-        scmd->result = saved_result;
-        return rtn;
+        return scsi_send_eh_cmnd(scmd, SENSE_TIMEOUT, 1);
 }
 
 /**
@@ -605,12 +630,6 @@ void scsi_eh_finish_cmd(struct scsi_cmnd *scmd, struct list_head *done_q)
 {
         scmd->device->host->host_failed--;
         scmd->eh_eflags = 0;
-
-        /*
-         * set this back so that the upper level can correctly free up
-         * things.
-         */
-        scsi_setup_cmd_retry(scmd);
         list_move_tail(&scmd->eh_entry, done_q);
 }
 EXPORT_SYMBOL(scsi_eh_finish_cmd);
@@ -715,47 +734,26 @@ static int scsi_eh_tur(struct scsi_cmnd *scmd)
 {
         static unsigned char tur_command[6] = {TEST_UNIT_READY, 0, 0, 0, 0, 0};
         int retry_cnt = 1, rtn;
-        int saved_result;
 
 retry_tur:
         memcpy(scmd->cmnd, tur_command, sizeof(tur_command));
 
-        /*
-         * zero the sense buffer.  the scsi spec mandates that any
-         * untransferred sense data should be interpreted as being zero.
-         */
-        memset(scmd->sense_buffer, 0, sizeof(scmd->sense_buffer));
-
-        saved_result = scmd->result;
-        scmd->request_buffer = NULL;
-        scmd->request_bufflen = 0;
-        scmd->use_sg = 0;
-        scmd->cmd_len = COMMAND_SIZE(scmd->cmnd[0]);
-        scmd->underflow = 0;
-        scmd->sc_data_direction = DMA_NONE;
 
-        rtn = scsi_send_eh_cmnd(scmd, SENSE_TIMEOUT);
+        rtn = scsi_send_eh_cmnd(scmd, SENSE_TIMEOUT, 0);
 
-        /*
-         * when we eventually call scsi_finish, we really wish to complete
-         * the original request, so let's restore the original data. (db)
-         */
-        scsi_setup_cmd_retry(scmd);
-        scmd->result = saved_result;
-
-        /*
-         * hey, we are done.  let's look to see what happened.
-         */
         SCSI_LOG_ERROR_RECOVERY(3, printk("%s: scmd %p rtn %x\n",
                 __FUNCTION__, scmd, rtn));
-        if (rtn == SUCCESS)
-                return 0;
-        else if (rtn == NEEDS_RETRY) {
+
+        switch (rtn) {
+        case NEEDS_RETRY:
                 if (retry_cnt--)
                         goto retry_tur;
+                /*FALLTHRU*/
+        case SUCCESS:
                 return 0;
+        default:
+                return 1;
         }
-        return 1;
 }
 
 /**
@@ -837,44 +835,16 @@ static int scsi_try_bus_device_reset(struct scsi_cmnd *scmd)
 static int scsi_eh_try_stu(struct scsi_cmnd *scmd)
 {
         static unsigned char stu_command[6] = {START_STOP, 0, 0, 0, 1, 0};
-        int rtn;
-        int saved_result;
 
-        if (!scmd->device->allow_restart)
-                return 1;
-
-        memcpy(scmd->cmnd, stu_command, sizeof(stu_command));
-
-        /*
-         * zero the sense buffer.  the scsi spec mandates that any
-         * untransferred sense data should be interpreted as being zero.
-         */
-        memset(scmd->sense_buffer, 0, sizeof(scmd->sense_buffer));
-
-        saved_result = scmd->result;
-        scmd->request_buffer = NULL;
-        scmd->request_bufflen = 0;
-        scmd->use_sg = 0;
-        scmd->cmd_len = COMMAND_SIZE(scmd->cmnd[0]);
-        scmd->underflow = 0;
-        scmd->sc_data_direction = DMA_NONE;
+        if (scmd->device->allow_restart) {
+                int rtn;
 
-        rtn = scsi_send_eh_cmnd(scmd, START_UNIT_TIMEOUT);
-
-        /*
-         * when we eventually call scsi_finish, we really wish to complete
-         * the original request, so let's restore the original data. (db)
-         */
-        scsi_setup_cmd_retry(scmd);
-        scmd->result = saved_result;
+                memcpy(scmd->cmnd, stu_command, sizeof(stu_command));
+                rtn = scsi_send_eh_cmnd(scmd, START_UNIT_TIMEOUT, 0);
+                if (rtn == SUCCESS)
+                        return 0;
+        }
 
-        /*
-         * hey, we are done.  let's look to see what happened.
-         */
-        SCSI_LOG_ERROR_RECOVERY(3, printk("%s: scmd %p rtn %x\n",
-                __FUNCTION__, scmd, rtn));
-        if (rtn == SUCCESS)
-                return 0;
         return 1;
 }
 
@@ -1684,8 +1654,6 @@ scsi_reset_provider(struct scsi_device *dev, int flag)
     
         scmd->scsi_done         = scsi_reset_provider_done_command;
         scmd->done                      = NULL;
-        scmd->buffer                    = NULL;
-        scmd->bufflen                   = 0;
         scmd->request_buffer            = NULL;
         scmd->request_bufflen           = 0;
 
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 08af9aae7df3..077c1c691210 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -436,60 +436,16 @@ EXPORT_SYMBOL_GPL(scsi_execute_async);
  *
  * Arguments:   cmd     - command that is ready to be queued.
  *
- * Returns:     Nothing
- *
  * Notes:       This function has the job of initializing a number of
  *              fields related to error handling.   Typically this will
  *              be called once for each command, as required.
  */
-static int scsi_init_cmd_errh(struct scsi_cmnd *cmd)
+static void scsi_init_cmd_errh(struct scsi_cmnd *cmd)
 {
         cmd->serial_number = 0;
-
         memset(cmd->sense_buffer, 0, sizeof cmd->sense_buffer);
-
         if (cmd->cmd_len == 0)
                 cmd->cmd_len = COMMAND_SIZE(cmd->cmnd[0]);
-
-        /*
-         * We need saved copies of a number of fields - this is because
-         * error handling may need to overwrite these with different values
-         * to run different commands, and once error handling is complete,
-         * we will need to restore these values prior to running the actual
-         * command.
-         */
-        cmd->old_use_sg = cmd->use_sg;
-        cmd->old_cmd_len = cmd->cmd_len;
-        cmd->sc_old_data_direction = cmd->sc_data_direction;
-        cmd->old_underflow = cmd->underflow;
-        memcpy(cmd->data_cmnd, cmd->cmnd, sizeof(cmd->cmnd));
-        cmd->buffer = cmd->request_buffer;
-        cmd->bufflen = cmd->request_bufflen;
-
-        return 1;
-}
-
-/*
- * Function:   scsi_setup_cmd_retry()
- *
- * Purpose:    Restore the command state for a retry
- *
- * Arguments:  cmd      - command to be restored
- *
- * Returns:    Nothing
- *
- * Notes:      Immediately prior to retrying a command, we need
- *             to restore certain fields that we saved above.
- */
-void scsi_setup_cmd_retry(struct scsi_cmnd *cmd)
-{
-        memcpy(cmd->cmnd, cmd->data_cmnd, sizeof(cmd->data_cmnd));
-        cmd->request_buffer = cmd->buffer;
-        cmd->request_bufflen = cmd->bufflen;
-        cmd->use_sg = cmd->old_use_sg;
-        cmd->cmd_len = cmd->old_cmd_len;
-        cmd->sc_data_direction = cmd->sc_old_data_direction;
-        cmd->underflow = cmd->old_underflow;
 }
 
 void scsi_device_unbusy(struct scsi_device *sdev)
@@ -807,22 +763,13 @@ static void scsi_free_sgtable(struct scatterlist *sgl, int index)
  */
 static void scsi_release_buffers(struct scsi_cmnd *cmd)
 {
-        struct request *req = cmd->request;
-
-        /*
-         * Free up any indirection buffers we allocated for DMA purposes. 
-         */
         if (cmd->use_sg)
                 scsi_free_sgtable(cmd->request_buffer, cmd->sglist_len);
-        else if (cmd->request_buffer != req->buffer)
-                kfree(cmd->request_buffer);
 
         /*
          * Zero these out.  They now point to freed memory, and it is
          * dangerous to hang onto the pointers.
          */
-        cmd->buffer  = NULL;
-        cmd->bufflen = 0;
         cmd->request_buffer = NULL;
         cmd->request_bufflen = 0;
 }
@@ -858,7 +805,7 @@ static void scsi_release_buffers(struct scsi_cmnd *cmd)
 void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes)
 {
         int result = cmd->result;
-        int this_count = cmd->bufflen;
+        int this_count = cmd->request_bufflen;
         request_queue_t *q = cmd->device->request_queue;
         struct request *req = cmd->request;
         int clear_errors = 1;
@@ -866,28 +813,14 @@ void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes)
         int sense_valid = 0;
         int sense_deferred = 0;
 
-        /*
-         * Free up any indirection buffers we allocated for DMA purposes. 
-         * For the case of a READ, we need to copy the data out of the
-         * bounce buffer and into the real buffer.
-         */
-        if (cmd->use_sg)
-                scsi_free_sgtable(cmd->buffer, cmd->sglist_len);
-        else if (cmd->buffer != req->buffer) {
-                if (rq_data_dir(req) == READ) {
-                        unsigned long flags;
-                        char *to = bio_kmap_irq(req->bio, &flags);
-                        memcpy(to, cmd->buffer, cmd->bufflen);
-                        bio_kunmap_irq(to, &flags);
-                }
-                kfree(cmd->buffer);
-        }
+        scsi_release_buffers(cmd);
 
         if (result) {
                 sense_valid = scsi_command_normalize_sense(cmd, &sshdr);
                 if (sense_valid)
                         sense_deferred = scsi_sense_is_deferred(&sshdr);
         }
+
         if (blk_pc_request(req)) { /* SG_IO ioctl from block level */
                 req->errors = result;
                 if (result) {
@@ -908,15 +841,6 @@ void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes)
         }
 
         /*
-         * Zero these out.  They now point to freed memory, and it is
-         * dangerous to hang onto the pointers.
-         */
-        cmd->buffer  = NULL;
-        cmd->bufflen = 0;
-        cmd->request_buffer = NULL;
-        cmd->request_bufflen = 0;
-
-        /*
          * Next deal with any sectors which we were able to correctly
          * handle.
          */
@@ -1012,7 +936,7 @@ void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes)
                         if (!(req->flags & REQ_QUIET)) {
                                 scmd_printk(KERN_INFO, cmd,
                                             "Volume overflow, CDB: ");
-                                __scsi_print_command(cmd->data_cmnd);
+                                __scsi_print_command(cmd->cmnd);
                                 scsi_print_sense("", cmd);
                         }
                         /* See SSC3rXX or current. */
@@ -1143,7 +1067,7 @@ static void scsi_blk_pc_done(struct scsi_cmnd *cmd)
          * successfully. Since this is a REQ_BLOCK_PC command the
          * caller should check the request's errors value
          */
-        scsi_io_completion(cmd, cmd->bufflen);
+        scsi_io_completion(cmd, cmd->request_bufflen);
 }
 
 static void scsi_setup_blk_pc_cmnd(struct scsi_cmnd *cmd)
diff --git a/drivers/scsi/scsi_priv.h b/drivers/scsi/scsi_priv.h
index e2fbe9a9d5a9..ae24c85aaeea 100644
--- a/drivers/scsi/scsi_priv.h
+++ b/drivers/scsi/scsi_priv.h
@@ -57,7 +57,6 @@ extern int scsi_eh_scmd_add(struct scsi_cmnd *, int);
 
 /* scsi_lib.c */
 extern int scsi_maybe_unblock_host(struct scsi_device *sdev);
-extern void scsi_setup_cmd_retry(struct scsi_cmnd *cmd);
 extern void scsi_device_unbusy(struct scsi_device *sdev);
 extern int scsi_queue_insert(struct scsi_cmnd *cmd, int reason);
 extern void scsi_next_command(struct scsi_cmnd *cmd);
diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index 3225d31449e1..98bd3aab9739 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -502,8 +502,7 @@ static int sd_init_command(struct scsi_cmnd * SCpnt)
                 SCpnt->cmnd[4] = (unsigned char) this_count;
                 SCpnt->cmnd[5] = 0;
         }
-        SCpnt->request_bufflen = SCpnt->bufflen =
-                        this_count * sdp->sector_size;
+        SCpnt->request_bufflen = this_count * sdp->sector_size;
 
         /*
          * We shouldn't disconnect in the middle of a sector, so with a dumb
diff --git a/drivers/scsi/sr.c b/drivers/scsi/sr.c
index fd94408577e5..fae6e95a6298 100644
--- a/drivers/scsi/sr.c
+++ b/drivers/scsi/sr.c
@@ -360,7 +360,7 @@ static int sr_init_command(struct scsi_cmnd * SCpnt)
                                 "mismatch count %d, bytes %d\n",
                                 size, SCpnt->request_bufflen);
                         if (SCpnt->request_bufflen > size)
-                                SCpnt->request_bufflen = SCpnt->bufflen = size;
+                                SCpnt->request_bufflen = size;
                 }
         }
 
@@ -387,8 +387,7 @@ static int sr_init_command(struct scsi_cmnd * SCpnt)
 
         if (this_count > 0xffff) {
                 this_count = 0xffff;
-                SCpnt->request_bufflen = SCpnt->bufflen =
-                                this_count * s_size;
+                SCpnt->request_bufflen = this_count * s_size;
         }
 
         SCpnt->cmnd[2] = (unsigned char) (block >> 24) & 0xff;
diff --git a/include/scsi/scsi_cmnd.h b/include/scsi/scsi_cmnd.h
index 371f70d9aa92..58e6444eebee 100644
--- a/include/scsi/scsi_cmnd.h
+++ b/include/scsi/scsi_cmnd.h
@@ -58,9 +58,7 @@ struct scsi_cmnd {
         int timeout_per_command;
 
         unsigned char cmd_len;
-        unsigned char old_cmd_len;
         enum dma_data_direction sc_data_direction;
-        enum dma_data_direction sc_old_data_direction;
 
         /* These elements define the operation we are about to perform */
 #define MAX_COMMAND_SIZE        16
@@ -71,18 +69,11 @@ struct scsi_cmnd {
         void *request_buffer;           /* Actual requested buffer */
 
         /* These elements define the operation we ultimately want to perform */
-        unsigned char data_cmnd[MAX_COMMAND_SIZE];
-        unsigned short old_use_sg;      /* We save  use_sg here when requesting
-                                         * sense info */
         unsigned short use_sg;  /* Number of pieces of scatter-gather */
         unsigned short sglist_len;      /* size of malloc'd scatter-gather list */
-        unsigned bufflen;       /* Size of data buffer */
-        void *buffer;           /* Data buffer */
 
         unsigned underflow;     /* Return error if less than
                                    this amount is transferred */
-        unsigned old_underflow; /* save underflow here when reusing the
-                                 * command for error handling */
 
         unsigned transfersize;  /* How much we are guaranteed to
                                    transfer with each SCSI transfer