[PATCH scsi] Short the path length of scsi_cmd_to_driver()

[Li Zhong]

Hi James, Martin,  

Here is the updated version, please help to review.

Thanks, Zhong

========
As suggested by James: this patch tries to short the path length of
scsi_cmd_to_driver(). As only REQ_TYPE_BLOCK_PC commands can be
submitted without a driver, so we could avoid the related NULL 
checking, as long as we make sure we don't use it for REQ_TYPE_BLOCK_PC
type commands. Plus, this fixes a bug where you get different behaviors
from REQ_TYPE_BLOCK_PC commands when a driver is and isn't attached. 

And Martin pointed out that we could have eh action be triggered for 
REQ_TYPE_FS type only. 

Signed-off-by: Li Zhong <zh...@linux.vnet.ibm.com>
---
 drivers/scsi/scsi_error.c |    8 +++++---
 include/scsi/scsi_cmnd.h  |   12 ++----------
 2 files changed, 7 insertions(+), 13 deletions(-)

diff --git a/drivers/scsi/scsi_error.c b/drivers/scsi/scsi_error.c
index de2337f..4001559 100644
--- a/drivers/scsi/scsi_error.c
+++ b/drivers/scsi/scsi_error.c
@@ -789,7 +789,6 @@ static int scsi_send_eh_cmnd(struct scsi_cmnd *scmd, 
unsigned char *cmnd,
                             int cmnd_size, int timeout, unsigned sense_bytes)
 {
        struct scsi_device *sdev = scmd->device;
-       struct scsi_driver *sdrv = scsi_cmd_to_driver(scmd);
        struct Scsi_Host *shost = sdev->host;
        DECLARE_COMPLETION_ONSTACK(done);
        unsigned long timeleft;
@@ -845,8 +844,11 @@ static int scsi_send_eh_cmnd(struct scsi_cmnd *scmd, 
unsigned char *cmnd,
 
        scsi_eh_restore_cmnd(scmd, &ses);
 
-       if (sdrv && sdrv->eh_action)
-               rtn = sdrv->eh_action(scmd, cmnd, cmnd_size, rtn);
+       if (scmd->request->cmd_type == REQ_TYPE_FS) {
+               struct scsi_driver *sdrv = scsi_cmd_to_driver(scmd);
+               if (sdrv->eh_action)
+                       rtn = sdrv->eh_action(scmd, cmnd, cmnd_size, rtn);
+       }
 
        return rtn;
 }
diff --git a/include/scsi/scsi_cmnd.h b/include/scsi/scsi_cmnd.h
index ac06cc5..de5f5d8 100644
--- a/include/scsi/scsi_cmnd.h
+++ b/include/scsi/scsi_cmnd.h
@@ -132,18 +132,10 @@ struct scsi_cmnd {
        unsigned char tag;      /* SCSI-II queued command tag */
 };
 
+/* make sure not to use it with REQ_TYPE_BLOCK_PC commands */
 static inline struct scsi_driver *scsi_cmd_to_driver(struct scsi_cmnd *cmd)
 {
-       struct scsi_driver **sdp;
-
-       if (!cmd->request->rq_disk)
-               return NULL;
-
-       sdp = (struct scsi_driver **)cmd->request->rq_disk->private_data;
-       if (!sdp)
-               return NULL;
-
-       return *sdp;
+       return *(struct scsi_driver **)cmd->request->rq_disk->private_data;
 }
 
 extern struct scsi_cmnd *scsi_get_command(struct scsi_device *, gfp_t);
-- 
1.7.7.6



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