linux-kernel - [QUESTION] xsysace: moving the end_that_request

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Message-Id: <20070809.174214.35657111.k-ueda@ct.jp.nec.com>
Date:	Thu, 09 Aug 2007 17:42:14 -0400 (EDT)
From:	Kiyoshi Ueda <k-ueda@...jp.nec.com>
To:	grant.likely@...retlab.ca, linux-kernel@...r.kernel.org
Cc:	j-nomura@...jp.nec.com, k-ueda@...jp.nec.com
Subject: [QUESTION] xsysace: moving the end_that_request_last() call

Hi,

Is there any problem if end_that_request_last() in ace_fsm_dostate()
is moved to ACE_FSM_STATE_REQ_TRANSFER state from
ACE_FSM_STATE_REQ_COMPLETE state like the patch below?

BACKGROUND:
I'm working on refining request completion procedures like:
    Before: 2 steps completion using "end_that_request_{first/chunk}"
            and "end_that_request_last"
    After:  1 step completion using generic block-layer helper
            which I'm calling "blk_end_request"
"blk_end_request" works like calling "__end_that_request_first"
and "end_that_request_last".
<http://marc.info/?l=linux-kernel&m=116846938806220&w=2>

However, while auditing various drivers, I found xsysace driver
doesn't call end_that_request_first() and end_that_request_last()
at a time.  It makes implementation of blk_end_request complicated.
So I'd like to move the end_that_request_last() call.

I think it's no problem because after the successful call to
end_that_request_first() in ACE_FSM_STATE_REQ_TRANSFER, the state
changes immediately to ACE_FSM_STATE_REQ_COMPLETE without interruption,
where it calls end_that_request_last().
There is no other transition to ACE_FSM_STATE_REQ_COMPLETE state.

Thanks,
Kiyoshi Ueda


Signed-off-by: Kiyoshi Ueda <k-ueda@...jp.nec.com>
Signed-off-by: Jun'ichi Nomura <j-nomura@...jp.nec.com>

--- 2.6.23-rc1-mm1/drivers/block/xsysace.c	2007-07-25 15:12:05.000000000 -0400
+++ xsysace/drivers/block/xsysace.c	2007-08-09 16:40:34.000000000 -0400
@@ -707,13 +707,14 @@ static void ace_fsm_dostate(struct ace_d
 			break;
 		}
 
+		/* Complete the block request */
+		blkdev_dequeue_request(ace->req);
+		end_that_request_last(ace->req, 1);
+
 		ace->fsm_state = ACE_FSM_STATE_REQ_COMPLETE;
 		break;
 
 	case ACE_FSM_STATE_REQ_COMPLETE:
-		/* Complete the block request */
-		blkdev_dequeue_request(ace->req);
-		end_that_request_last(ace->req, 1);
 		ace->req = NULL;
 
 		/* Finished request; go to idle state */
-
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