[PATCH] scsi: remove meaningless scsi_cmnd->serial_number_at_timeout field

scsi_cmnd->serial_number_at_timeout doesn't serve any purpose
anymore.  All serial_number == serial_number_at_timeout tests
are always true in abort callbacks.  Kill the field.  Also, as
->pid always equals ->serial_number and ->serial_number
doesn't have any special meaning anymore, update comments
above ->serial_number accordingly.  Once we remove all uses of
this field from all lldd's, this field should go.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>

1 files changed, 9 insertions, 13 deletions

diff --git a/include/scsi/scsi_cmnd.h b/include/scsi/scsi_cmnd.h
index ae45d6f8f98c..07f5c699eaa7 100644
--- a/include/scsi/scsi_cmnd.h
+++ b/include/scsi/scsi_cmnd.h
@@ -43,21 +43,17 @@ struct scsi_cmnd {
         void (*done) (struct scsi_cmnd *);      /* Mid-level done function */
 
         /*
-         * A SCSI Command is assigned a nonzero serial_number when internal_cmnd
-         * passes it to the driver's queue command function.  The serial_number
-         * is cleared when scsi_done is entered indicating that the command has
-         * been completed.  If a timeout occurs, the serial number at the moment
-         * of timeout is copied into serial_number_at_timeout.  By subsequently
-         * comparing the serial_number and serial_number_at_timeout fields
-         * during abort or reset processing, we can detect whether the command
-         * has already completed.  This also detects cases where the command has
-         * completed and the SCSI Command structure has already being reused
-         * for another command, so that we can avoid incorrectly aborting or
-         * resetting the new command.
-         * The serial number is only unique per host.
+         * A SCSI Command is assigned a nonzero serial_number before passed
+         * to the driver's queue command function.  The serial_number is
+         * cleared when scsi_done is entered indicating that the command
+         * has been completed.  It currently doesn't have much use other
+         * than printk's.  Some lldd's use this number for other purposes.
+         * It's almost certain that such usages are either incorrect or
+         * meaningless.  Please kill all usages other than printk's.  Also,
+         * as this number is always identical to ->pid, please convert
+         * printk's to use ->pid, so that we can kill this field.
          */
         unsigned long serial_number;
-        unsigned long serial_number_at_timeout;
 
         int retries;
         int allowed;