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authorTejun Heo <tj@kernel.org>2011-01-25 12:43:54 +0100
committerJens Axboe <jaxboe@fusionio.com>2011-01-25 12:43:54 +0100
commitae1b1539622fb46e51b4d13b3f9e5f4c713f86ae (patch)
treec5cb540141003a3ec7ebf0b8c6e01653ab6aaef5 /block/blk-core.c
parent143a87f4c9c629067afea5b6703d66ea88c82f8e (diff)
block: reimplement FLUSH/FUA to support merge
The current FLUSH/FUA support has evolved from the implementation which had to perform queue draining. As such, sequencing is done queue-wide one flush request after another. However, with the draining requirement gone, there's no reason to keep the queue-wide sequential approach. This patch reimplements FLUSH/FUA support such that each FLUSH/FUA request is sequenced individually. The actual FLUSH execution is double buffered and whenever a request wants to execute one for either PRE or POSTFLUSH, it queues on the pending queue. Once certain conditions are met, a flush request is issued and on its completion all pending requests proceed to the next sequence. This allows arbitrary merging of different type of flushes. How they are merged can be primarily controlled and tuned by adjusting the above said 'conditions' used to determine when to issue the next flush. This is inspired by Darrick's patches to merge multiple zero-data flushes which helps workloads with highly concurrent fsync requests. * As flush requests are never put on the IO scheduler, request fields used for flush share space with rq->rb_node. rq->completion_data is moved out of the union. This increases the request size by one pointer. As rq->elevator_private* are used only by the iosched too, it is possible to reduce the request size further. However, to do that, we need to modify request allocation path such that iosched data is not allocated for flush requests. * FLUSH/FUA processing happens on insertion now instead of dispatch. - Comments updated as per Vivek and Mike. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: "Darrick J. Wong" <djwong@us.ibm.com> Cc: Shaohua Li <shli@kernel.org> Cc: Christoph Hellwig <hch@lst.de> Cc: Vivek Goyal <vgoyal@redhat.com> Cc: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
Diffstat (limited to 'block/blk-core.c')
-rw-r--r--block/blk-core.c10
1 files changed, 4 insertions, 6 deletions
diff --git a/block/blk-core.c b/block/blk-core.c
index 617bb9e40927..05746093b45e 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -134,8 +134,6 @@ EXPORT_SYMBOL(blk_rq_init);
static void req_bio_endio(struct request *rq, struct bio *bio,
unsigned int nbytes, int error)
{
- struct request_queue *q = rq->q;
-
if (error)
clear_bit(BIO_UPTODATE, &bio->bi_flags);
else if (!test_bit(BIO_UPTODATE, &bio->bi_flags))
@@ -159,8 +157,6 @@ static void req_bio_endio(struct request *rq, struct bio *bio,
/* don't actually finish bio if it's part of flush sequence */
if (bio->bi_size == 0 && !(rq->cmd_flags & REQ_FLUSH_SEQ))
bio_endio(bio, error);
- else if (error && !q->flush_err)
- q->flush_err = error;
}
void blk_dump_rq_flags(struct request *rq, char *msg)
@@ -519,7 +515,9 @@ struct request_queue *blk_alloc_queue_node(gfp_t gfp_mask, int node_id)
init_timer(&q->unplug_timer);
setup_timer(&q->timeout, blk_rq_timed_out_timer, (unsigned long) q);
INIT_LIST_HEAD(&q->timeout_list);
- INIT_LIST_HEAD(&q->pending_flushes);
+ INIT_LIST_HEAD(&q->flush_queue[0]);
+ INIT_LIST_HEAD(&q->flush_queue[1]);
+ INIT_LIST_HEAD(&q->flush_data_in_flight);
INIT_WORK(&q->unplug_work, blk_unplug_work);
kobject_init(&q->kobj, &blk_queue_ktype);
@@ -1198,7 +1196,7 @@ static int __make_request(struct request_queue *q, struct bio *bio)
spin_lock_irq(q->queue_lock);
if (bio->bi_rw & (REQ_FLUSH | REQ_FUA)) {
- where = ELEVATOR_INSERT_FRONT;
+ where = ELEVATOR_INSERT_FLUSH;
goto get_rq;
}