block: change the tag sync vs async restriction logic
Make them fully share the tag space, but disallow async requests using
the last any two slots.
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/block/blk-barrier.c b/block/blk-barrier.c
index 0ab81a0..0d98054 100644
--- a/block/blk-barrier.c
+++ b/block/blk-barrier.c
@@ -218,7 +218,7 @@
} else
skip |= QUEUE_ORDSEQ_PREFLUSH;
- if ((q->ordered & QUEUE_ORDERED_BY_DRAIN) && q->in_flight)
+ if ((q->ordered & QUEUE_ORDERED_BY_DRAIN) && queue_in_flight(q))
rq = NULL;
else
skip |= QUEUE_ORDSEQ_DRAIN;
diff --git a/block/blk-core.c b/block/blk-core.c
index 4906507..1c74840 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -1815,7 +1815,7 @@
* the driver side.
*/
if (blk_account_rq(rq))
- q->in_flight++;
+ q->in_flight[rq_is_sync(rq)]++;
}
/**
diff --git a/block/blk-tag.c b/block/blk-tag.c
index c260f7c..2e5cfeb 100644
--- a/block/blk-tag.c
+++ b/block/blk-tag.c
@@ -336,7 +336,7 @@
int blk_queue_start_tag(struct request_queue *q, struct request *rq)
{
struct blk_queue_tag *bqt = q->queue_tags;
- unsigned max_depth, offset;
+ unsigned max_depth;
int tag;
if (unlikely((rq->cmd_flags & REQ_QUEUED))) {
@@ -355,13 +355,16 @@
* to starve sync IO on behalf of flooding async IO.
*/
max_depth = bqt->max_depth;
- if (rq_is_sync(rq))
- offset = 0;
- else
- offset = max_depth >> 2;
+ if (!rq_is_sync(rq) && max_depth > 1) {
+ max_depth -= 2;
+ if (!max_depth)
+ max_depth = 1;
+ if (q->in_flight[0] > max_depth)
+ return 1;
+ }
do {
- tag = find_next_zero_bit(bqt->tag_map, max_depth, offset);
+ tag = find_first_zero_bit(bqt->tag_map, max_depth);
if (tag >= max_depth)
return 1;
diff --git a/block/elevator.c b/block/elevator.c
index 9189200..ebee948 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -546,7 +546,7 @@
* in_flight count again
*/
if (blk_account_rq(rq)) {
- q->in_flight--;
+ q->in_flight[rq_is_sync(rq)]--;
if (blk_sorted_rq(rq))
elv_deactivate_rq(q, rq);
}
@@ -685,7 +685,7 @@
if (unplug_it && blk_queue_plugged(q)) {
int nrq = q->rq.count[BLK_RW_SYNC] + q->rq.count[BLK_RW_ASYNC]
- - q->in_flight;
+ - queue_in_flight(q);
if (nrq >= q->unplug_thresh)
__generic_unplug_device(q);
@@ -823,7 +823,7 @@
* request is released from the driver, io must be done
*/
if (blk_account_rq(rq)) {
- q->in_flight--;
+ q->in_flight[rq_is_sync(rq)]--;
if (blk_sorted_rq(rq) && e->ops->elevator_completed_req_fn)
e->ops->elevator_completed_req_fn(q, rq);
}
@@ -838,7 +838,7 @@
if (!list_empty(&q->queue_head))
next = list_entry_rq(q->queue_head.next);
- if (!q->in_flight &&
+ if (!queue_in_flight(q) &&
blk_ordered_cur_seq(q) == QUEUE_ORDSEQ_DRAIN &&
(!next || blk_ordered_req_seq(next) > QUEUE_ORDSEQ_DRAIN)) {
blk_ordered_complete_seq(q, QUEUE_ORDSEQ_DRAIN, 0);
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 564445b..a967dd7 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -404,7 +404,7 @@
struct list_head tag_busy_list;
unsigned int nr_sorted;
- unsigned int in_flight;
+ unsigned int in_flight[2];
unsigned int rq_timeout;
struct timer_list timeout;
@@ -511,6 +511,11 @@
__clear_bit(flag, &q->queue_flags);
}
+static inline int queue_in_flight(struct request_queue *q)
+{
+ return q->in_flight[0] + q->in_flight[1];
+}
+
static inline void queue_flag_clear(unsigned int flag, struct request_queue *q)
{
WARN_ON_ONCE(!queue_is_locked(q));