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block: make every barrier action optional 

In all barrier sequences, the barrier write itself was always assumed
to be issued and thus didn't have corresponding control flag.  This
patch adds QUEUE_ORDERED_DO_BAR and unify action mask handling in
start_ordered() such that any barrier action can be skipped.

This patch doesn't introduce any visible behavior changes.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
This commit is contained in:
Tejun Heo 2008-11-28 13:32:04 +09:00 committed by Jens Axboe
parent a7384677b2
commit f671620e7d
2 changed files with 29 additions and 19 deletions
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41
block/blk-barrier.c
View File

@ -158,19 +158,10 @@ static inline struct request *start_ordered(struct request_queue *q,
q->ordered = q->next_ordered;
q->ordseq |= QUEUE_ORDSEQ_STARTED;
/*
* Prep proxy barrier request.
*/
/* stash away the original request */
elv_dequeue_request(q, rq);
q->orig_bar_rq = rq;
rq = &q->bar_rq;
blk_rq_init(q, rq);
if (bio_data_dir(q->orig_bar_rq->bio) == WRITE)
rq->cmd_flags |= REQ_RW;
if (q->ordered & QUEUE_ORDERED_DO_FUA)
rq->cmd_flags |= REQ_FUA;
init_request_from_bio(rq, q->orig_bar_rq->bio);
rq->end_io = bar_end_io;
rq = NULL;
/*
* Queue ordered sequence. As we stack them at the head, we
@ -181,12 +172,28 @@ static inline struct request *start_ordered(struct request_queue *q,
* there will be no data written between the pre and post flush.
* Hence a single flush will suffice.
*/
if ((q->ordered & QUEUE_ORDERED_DO_POSTFLUSH) && !blk_empty_barrier(rq))
if ((q->ordered & QUEUE_ORDERED_DO_POSTFLUSH) &&
!blk_empty_barrier(q->orig_bar_rq)) {
queue_flush(q, QUEUE_ORDERED_DO_POSTFLUSH);
else
rq = &q->post_flush_rq;
} else
q->ordseq |= QUEUE_ORDSEQ_POSTFLUSH;
elv_insert(q, rq, ELEVATOR_INSERT_FRONT);
if (q->ordered & QUEUE_ORDERED_DO_BAR) {
rq = &q->bar_rq;
/* initialize proxy request and queue it */
blk_rq_init(q, rq);
if (bio_data_dir(q->orig_bar_rq->bio) == WRITE)
rq->cmd_flags |= REQ_RW;
if (q->ordered & QUEUE_ORDERED_DO_FUA)
rq->cmd_flags |= REQ_FUA;
init_request_from_bio(rq, q->orig_bar_rq->bio);
rq->end_io = bar_end_io;
elv_insert(q, rq, ELEVATOR_INSERT_FRONT);
} else
q->ordseq |= QUEUE_ORDSEQ_BAR;
if (q->ordered & QUEUE_ORDERED_DO_PREFLUSH) {
queue_flush(q, QUEUE_ORDERED_DO_PREFLUSH);
@ -194,10 +201,10 @@ static inline struct request *start_ordered(struct request_queue *q,
} else
q->ordseq |= QUEUE_ORDSEQ_PREFLUSH;
if ((q->ordered & QUEUE_ORDERED_BY_TAG) || q->in_flight == 0)
q->ordseq |= QUEUE_ORDSEQ_DRAIN;
else
if ((q->ordered & QUEUE_ORDERED_BY_DRAIN) && q->in_flight)
rq = NULL;
else
q->ordseq |= QUEUE_ORDSEQ_DRAIN;
return rq;
}

7
include/linux/blkdev.h
View File

@ -526,12 +526,14 @@ enum {
QUEUE_ORDERED_BY_DRAIN = 0x01,
QUEUE_ORDERED_BY_TAG = 0x02,
QUEUE_ORDERED_DO_PREFLUSH = 0x10,
QUEUE_ORDERED_DO_BAR = 0x20,
QUEUE_ORDERED_DO_POSTFLUSH = 0x40,
QUEUE_ORDERED_DO_FUA = 0x80,
QUEUE_ORDERED_NONE = 0x00,
QUEUE_ORDERED_DRAIN = QUEUE_ORDERED_BY_DRAIN,
QUEUE_ORDERED_DRAIN = QUEUE_ORDERED_BY_DRAIN |
QUEUE_ORDERED_DO_BAR,
QUEUE_ORDERED_DRAIN_FLUSH = QUEUE_ORDERED_DRAIN |
QUEUE_ORDERED_DO_PREFLUSH |
QUEUE_ORDERED_DO_POSTFLUSH,
@ -539,7 +541,8 @@ enum {
QUEUE_ORDERED_DO_PREFLUSH |
QUEUE_ORDERED_DO_FUA,
QUEUE_ORDERED_TAG = QUEUE_ORDERED_BY_TAG,
QUEUE_ORDERED_TAG = QUEUE_ORDERED_BY_TAG |
QUEUE_ORDERED_DO_BAR,
QUEUE_ORDERED_TAG_FLUSH = QUEUE_ORDERED_TAG |
QUEUE_ORDERED_DO_PREFLUSH |
QUEUE_ORDERED_DO_POSTFLUSH,