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Subject[PATCH] block: eliminate ELEVATOR_INSERT_REQUEUE (was: Re: elevator private data for REQ_FLUSH)
On Mon, Mar 28 2011 at  4:23am -0400,
Tejun Heo <tj@kernel.org> wrote:

> On Sat, Mar 26, 2011 at 12:21:56AM -0400, Mike Snitzer wrote:
> > Should blk_kick_flush() process the flush request without calling
> > elv_insert() -- like is done with open coded list_add() in
> > blk_insert_flush()?
> >
> > Or should blk_insert_flush() use elv_insert() with
> > ELEVATOR_INSERT_REQUEUE too?
>
> Hmmm... I would prefer the latter. Given that INSERT_REQUEUE and
> FRONT are no longer different, it would probably be better to use
> FRONT tho. The only reason REQUEUE is used there is to avoid kicking
> the queue from elv_insert(), which is gone now.

OK, I came up with the following patch.

Jens, this is just a natural cleanup given the code that resulted from
the flush-merge and onstack plugging changes coming together.


From: Mike Snitzer <snitzer@redhat.com>
Subject: block: eliminate ELEVATOR_INSERT_REQUEUE

elv_insert() no longer has a need to differentiate between
ELEVATOR_INSERT_REQUEUE and ELEVATOR_INSERT_FRONT. The onstack plugging
changes eliminated the need to avoid unplugging the queue (via
ELEVATOR_INSERT_REQUEUE).

Also, in blk_insert_flush(), use elv_insert() with ELEVATOR_INSERT_FRONT
rather than open-coding the equivalent.

Signed-off-by: Mike Snitzer <snitzer@redhat.com>
---
block/blk-flush.c | 4 ++--
block/elevator.c | 3 +--
include/linux/elevator.h | 5 ++---
3 files changed, 5 insertions(+), 7 deletions(-)

diff --git a/block/blk-flush.c b/block/blk-flush.c
index 93d5fd8..2c43044 100644
--- a/block/blk-flush.c
+++ b/block/blk-flush.c
@@ -261,7 +261,7 @@ static bool blk_kick_flush(struct request_queue *q)
q->flush_rq.end_io = flush_end_io;

q->flush_pending_idx ^= 1;
- elv_insert(q, &q->flush_rq, ELEVATOR_INSERT_REQUEUE);
+ elv_insert(q, &q->flush_rq, ELEVATOR_INSERT_FRONT);
return true;
}

@@ -312,7 +312,7 @@ void blk_insert_flush(struct request *rq)
*/
if ((policy & REQ_FSEQ_DATA) &&
!(policy & (REQ_FSEQ_PREFLUSH | REQ_FSEQ_POSTFLUSH))) {
- list_add(&rq->queuelist, &q->queue_head);
+ elv_insert(q, rq, ELEVATOR_INSERT_FRONT);
return;
}

diff --git a/block/elevator.c b/block/elevator.c
index c387d31..df7c4ba 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -610,7 +610,7 @@ void elv_requeue_request(struct request_queue *q, struct request *rq)

rq->cmd_flags &= ~REQ_STARTED;

- elv_insert(q, rq, ELEVATOR_INSERT_REQUEUE);
+ elv_insert(q, rq, ELEVATOR_INSERT_FRONT);
}

void elv_drain_elevator(struct request_queue *q)
@@ -662,7 +662,6 @@ void elv_insert(struct request_queue *q, struct request *rq, int where)
rq->q = q;

switch (where) {
- case ELEVATOR_INSERT_REQUEUE:
case ELEVATOR_INSERT_FRONT:
rq->cmd_flags |= REQ_SOFTBARRIER;
list_add(&rq->queuelist, &q->queue_head);
diff --git a/include/linux/elevator.h b/include/linux/elevator.h
index d93efcc445..0b4a354 100644
--- a/include/linux/elevator.h
+++ b/include/linux/elevator.h
@@ -164,9 +164,8 @@ extern struct request *elv_rb_find(struct rb_root *, sector_t);
#define ELEVATOR_INSERT_FRONT 1
#define ELEVATOR_INSERT_BACK 2
#define ELEVATOR_INSERT_SORT 3
-#define ELEVATOR_INSERT_REQUEUE 4
-#define ELEVATOR_INSERT_FLUSH 5
-#define ELEVATOR_INSERT_SORT_MERGE 6
+#define ELEVATOR_INSERT_FLUSH 4
+#define ELEVATOR_INSERT_SORT_MERGE 5

/*
* return values from elevator_may_queue_fn


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