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block/mq-deadline: Switch back to a single dispatch list 

Commit c807ab520f ("block/mq-deadline: Add I/O priority support")
modified the behavior of request flag BLK_MQ_INSERT_AT_HEAD from
dispatching a request before other requests into dispatching a request
before other requests with the same I/O priority. This is not correct since
BLK_MQ_INSERT_AT_HEAD is used when requeuing requests and also when a flush
request is inserted.  Both types of requests should be dispatched as soon
as possible. Hence, make the mq-deadline I/O scheduler again ignore the I/O
priority for BLK_MQ_INSERT_AT_HEAD requests.

Cc: Damien Le Moal <dlemoal@kernel.org>
Cc: Yu Kuai <yukuai@kernel.org>
Reported-by: chengkaitao <chengkaitao@kylinos.cn>
Closes: https://lore.kernel.org/linux-block/20251009155253.14611-1-pilgrimtao@gmail.com/
Fixes: c807ab520f ("block/mq-deadline: Add I/O priority support")
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: Damien Le Moalv <dlemoal@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Bart Van Assche 2025-10-13 12:28:03 -07:00 committed by Jens Axboe
parent 93a358af59
commit d60055cf52
1 changed files with 47 additions and 60 deletions
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107
block/mq-deadline.c
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@ -71,7 +71,6 @@ struct io_stats_per_prio {
* present on both sort_list[] and fifo_list[].
*/
struct dd_per_prio {
struct list_head dispatch;
struct rb_root sort_list[DD_DIR_COUNT];
struct list_head fifo_list[DD_DIR_COUNT];
/* Position of the most recently dispatched request. */
@ -84,6 +83,7 @@ struct deadline_data {
* run time data
*/
struct list_head dispatch;
struct dd_per_prio per_prio[DD_PRIO_COUNT];
/* Data direction of latest dispatched request. */
@ -332,16 +332,6 @@ static struct request *__dd_dispatch_request(struct deadline_data *dd,
lockdep_assert_held(&dd->lock);
if (!list_empty(&per_prio->dispatch)) {
rq = list_first_entry(&per_prio->dispatch, struct request,
queuelist);
if (started_after(dd, rq, latest_start))
return NULL;
list_del_init(&rq->queuelist);
data_dir = rq_data_dir(rq);
goto done;
}
/*
* batches are currently reads XOR writes
*/
@ -421,7 +411,6 @@ static struct request *__dd_dispatch_request(struct deadline_data *dd,
*/
dd->batching++;
deadline_move_request(dd, per_prio, rq);
done:
return dd_start_request(dd, data_dir, rq);
}
@ -469,6 +458,14 @@ static struct request *dd_dispatch_request(struct blk_mq_hw_ctx *hctx)
enum dd_prio prio;
spin_lock(&dd->lock);
if (!list_empty(&dd->dispatch)) {
rq = list_first_entry(&dd->dispatch, struct request, queuelist);
list_del_init(&rq->queuelist);
dd_start_request(dd, rq_data_dir(rq), rq);
goto unlock;
}
rq = dd_dispatch_prio_aged_requests(dd, now);
if (rq)
goto unlock;
@ -557,10 +554,10 @@ static int dd_init_sched(struct request_queue *q, struct elevator_queue *eq)
eq->elevator_data = dd;
INIT_LIST_HEAD(&dd->dispatch);
for (prio = 0; prio <= DD_PRIO_MAX; prio++) {
struct dd_per_prio *per_prio = &dd->per_prio[prio];
INIT_LIST_HEAD(&per_prio->dispatch);
INIT_LIST_HEAD(&per_prio->fifo_list[DD_READ]);
INIT_LIST_HEAD(&per_prio->fifo_list[DD_WRITE]);
per_prio->sort_list[DD_READ] = RB_ROOT;
@ -664,7 +661,7 @@ static void dd_insert_request(struct blk_mq_hw_ctx *hctx, struct request *rq,
trace_block_rq_insert(rq);
if (flags & BLK_MQ_INSERT_AT_HEAD) {
list_add(&rq->queuelist, &per_prio->dispatch);
list_add(&rq->queuelist, &dd->dispatch);
rq->fifo_time = jiffies;
} else {
deadline_add_rq_rb(per_prio, rq);
@ -731,8 +728,7 @@ static void dd_finish_request(struct request *rq)
static bool dd_has_work_for_prio(struct dd_per_prio *per_prio)
{
return !list_empty_careful(&per_prio->dispatch) ||
!list_empty_careful(&per_prio->fifo_list[DD_READ]) ||
return !list_empty_careful(&per_prio->fifo_list[DD_READ]) ||
!list_empty_careful(&per_prio->fifo_list[DD_WRITE]);
}
@ -741,6 +737,9 @@ static bool dd_has_work(struct blk_mq_hw_ctx *hctx)
struct deadline_data *dd = hctx->queue->elevator->elevator_data;
enum dd_prio prio;
if (!list_empty_careful(&dd->dispatch))
return true;
for (prio = 0; prio <= DD_PRIO_MAX; prio++)
if (dd_has_work_for_prio(&dd->per_prio[prio]))
return true;
@ -949,49 +948,39 @@ static int dd_owned_by_driver_show(void *data, struct seq_file *m)
return 0;
}
#define DEADLINE_DISPATCH_ATTR(prio) \
static void *deadline_dispatch##prio##_start(struct seq_file *m, \
loff_t *pos) \
__acquires(&dd->lock) \
{ \
struct request_queue *q = m->private; \
struct deadline_data *dd = q->elevator->elevator_data; \
struct dd_per_prio *per_prio = &dd->per_prio[prio]; \
\
spin_lock(&dd->lock); \
return seq_list_start(&per_prio->dispatch, *pos); \
} \
\
static void *deadline_dispatch##prio##_next(struct seq_file *m, \
void *v, loff_t *pos) \
{ \
struct request_queue *q = m->private; \
struct deadline_data *dd = q->elevator->elevator_data; \
struct dd_per_prio *per_prio = &dd->per_prio[prio]; \
\
return seq_list_next(v, &per_prio->dispatch, pos); \
} \
\
static void deadline_dispatch##prio##_stop(struct seq_file *m, void *v) \
__releases(&dd->lock) \
{ \
struct request_queue *q = m->private; \
struct deadline_data *dd = q->elevator->elevator_data; \
\
spin_unlock(&dd->lock); \
} \
\
static const struct seq_operations deadline_dispatch##prio##_seq_ops = { \
.start = deadline_dispatch##prio##_start, \
.next = deadline_dispatch##prio##_next, \
.stop = deadline_dispatch##prio##_stop, \
.show = blk_mq_debugfs_rq_show, \
static void *deadline_dispatch_start(struct seq_file *m, loff_t *pos)
__acquires(&dd->lock)
{
struct request_queue *q = m->private;
struct deadline_data *dd = q->elevator->elevator_data;
spin_lock(&dd->lock);
return seq_list_start(&dd->dispatch, *pos);
}
DEADLINE_DISPATCH_ATTR(0);
DEADLINE_DISPATCH_ATTR(1);
DEADLINE_DISPATCH_ATTR(2);
#undef DEADLINE_DISPATCH_ATTR
static void *deadline_dispatch_next(struct seq_file *m, void *v, loff_t *pos)
{
struct request_queue *q = m->private;
struct deadline_data *dd = q->elevator->elevator_data;
return seq_list_next(v, &dd->dispatch, pos);
}
static void deadline_dispatch_stop(struct seq_file *m, void *v)
__releases(&dd->lock)
{
struct request_queue *q = m->private;
struct deadline_data *dd = q->elevator->elevator_data;
spin_unlock(&dd->lock);
}
static const struct seq_operations deadline_dispatch_seq_ops = {
.start = deadline_dispatch_start,
.next = deadline_dispatch_next,
.stop = deadline_dispatch_stop,
.show = blk_mq_debugfs_rq_show,
};
#define DEADLINE_QUEUE_DDIR_ATTRS(name) \
{#name "_fifo_list", 0400, \
@ -1014,9 +1003,7 @@ static const struct blk_mq_debugfs_attr deadline_queue_debugfs_attrs[] = {
{"batching", 0400, deadline_batching_show},
{"starved", 0400, deadline_starved_show},
{"async_depth", 0400, dd_async_depth_show},
{"dispatch0", 0400, .seq_ops = &deadline_dispatch0_seq_ops},
{"dispatch1", 0400, .seq_ops = &deadline_dispatch1_seq_ops},
{"dispatch2", 0400, .seq_ops = &deadline_dispatch2_seq_ops},
{"dispatch", 0400, .seq_ops = &deadline_dispatch_seq_ops},
{"owned_by_driver", 0400, dd_owned_by_driver_show},
{"queued", 0400, dd_queued_show},
{},