[SCSI] Let scsi_cmnd->cmnd use request->cmd buffer

 - struct scsi_cmnd had a 16 bytes command buffer of its own.
   This is an unnecessary duplication and copy of request's
   cmd. It is probably left overs from the time that scsi_cmnd
   could function without a request attached. So clean that up.

 - Once above is done, few places, apart from scsi-ml, needed
   adjustments due to changing the data type of scsi_cmnd->cmnd.

 - Lots of drivers still use MAX_COMMAND_SIZE. So I have left
   that #define but equate it to BLK_MAX_CDB. The way I see it
   and is reflected in the patch below is.
   MAX_COMMAND_SIZE - means: The longest fixed-length (*) SCSI CDB
                      as per the SCSI standard and is not related
                      to the implementation.
   BLK_MAX_CDB.     - The allocated space at the request level

 - I have audit all ISA drivers and made sure none use ->cmnd in a DMA
   Operation. Same audit was done by Andi Kleen.

(*)fixed-length here means commands that their size can be determined
   by their opcode and the CDB does not carry a length specifier, (unlike
   the VARIABLE_LENGTH_CMD(0x7f) command). This is actually not exactly
   true and the SCSI standard also defines extended commands and
   vendor specific commands that can be bigger than 16 bytes. The kernel
   will support these using the same infrastructure used for VARLEN CDB's.
   So in effect MAX_COMMAND_SIZE means the maximum size command
   scsi-ml supports without specifying a cmd_len by ULD's

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

1 files changed, 8 insertions, 7 deletions

diff --git a/drivers/scsi/scsi_error.c b/drivers/scsi/scsi_error.c
index 221f31e36d26..334244c73955 100644
--- a/drivers/scsi/scsi_error.c
+++ b/drivers/scsi/scsi_error.c
@@ -626,7 +626,7 @@ static void scsi_abort_eh_cmnd(struct scsi_cmnd *scmd)
  * @scmd:       SCSI command structure to hijack
  * @ses:        structure to save restore information
  * @cmnd:       CDB to send. Can be NULL if no new cmnd is needed
- * @cmnd_size:  size in bytes of @cmnd
+ * @cmnd_size:  size in bytes of @cmnd (must be <= BLK_MAX_CDB)
  * @sense_bytes: size of sense data to copy. or 0 (if != 0 @cmnd is ignored)
  *
  * This function is used to save a scsi command information before re-execution
@@ -648,12 +648,14 @@ void scsi_eh_prep_cmnd(struct scsi_cmnd *scmd, struct scsi_eh_save *ses,
          * command.
          */
         ses->cmd_len = scmd->cmd_len;
-        memcpy(ses->cmnd, scmd->cmnd, sizeof(scmd->cmnd));
+        ses->cmnd = scmd->cmnd;
         ses->data_direction = scmd->sc_data_direction;
         ses->sdb = scmd->sdb;
         ses->next_rq = scmd->request->next_rq;
         ses->result = scmd->result;
 
+        scmd->cmnd = ses->eh_cmnd;
+        memset(scmd->cmnd, 0, BLK_MAX_CDB);
         memset(&scmd->sdb, 0, sizeof(scmd->sdb));
         scmd->request->next_rq = NULL;
 
@@ -665,14 +667,13 @@ void scsi_eh_prep_cmnd(struct scsi_cmnd *scmd, struct scsi_eh_save *ses,
                 scmd->sdb.table.sgl = &ses->sense_sgl;
                 scmd->sc_data_direction = DMA_FROM_DEVICE;
                 scmd->sdb.table.nents = 1;
-                memset(scmd->cmnd, 0, sizeof(scmd->cmnd));
                 scmd->cmnd[0] = REQUEST_SENSE;
                 scmd->cmnd[4] = scmd->sdb.length;
                 scmd->cmd_len = COMMAND_SIZE(scmd->cmnd[0]);
         } else {
                 scmd->sc_data_direction = DMA_NONE;
                 if (cmnd) {
-                        memset(scmd->cmnd, 0, sizeof(scmd->cmnd));
+                        BUG_ON(cmnd_size > BLK_MAX_CDB);
                         memcpy(scmd->cmnd, cmnd, cmnd_size);
                         scmd->cmd_len = COMMAND_SIZE(scmd->cmnd[0]);
                 }
@@ -705,7 +706,7 @@ void scsi_eh_restore_cmnd(struct scsi_cmnd* scmd, struct scsi_eh_save *ses)
          * Restore original data
          */
         scmd->cmd_len = ses->cmd_len;
-        memcpy(scmd->cmnd, ses->cmnd, sizeof(scmd->cmnd));
+        scmd->cmnd = ses->cmnd;
         scmd->sc_data_direction = ses->data_direction;
         scmd->sdb = ses->sdb;
         scmd->request->next_rq = ses->next_rq;
@@ -1774,8 +1775,8 @@ scsi_reset_provider(struct scsi_device *dev, int flag)
         scmd->request = &req;
         memset(&scmd->eh_timeout, 0, sizeof(scmd->eh_timeout));
 
-        memset(&scmd->cmnd, '\0', sizeof(scmd->cmnd));
-    
+        scmd->cmnd = req.cmd;
+
         scmd->scsi_done         = scsi_reset_provider_done_command;
         memset(&scmd->sdb, 0, sizeof(scmd->sdb));