[RESEND PATCH v2 0/7] some improvements and cleanups for block

[RESEND PATCH v2 0/7] some improvements and cleanups for block

[Yufen Yu]

Hi all,
  This series contains improvement for elevator exit, removing
  wrong comments and clean-up code.

Yufen Yu (7):
  block: invoke blk_mq_exit_sched no matter whether have .exit_sched
  block: remove redundant mq check
  block: use helper function to test queue register
  blk-mq: use helper function to test hw stopped
  block: fix comment and add lockdep assert
  block: get rid of unnecessary local variable
  blk-mq: get rid of the dead flush handle code path

 block/blk-iocost.c   |  2 +-
 block/blk-mq-sched.c |  6 ------
 block/blk-mq.c       |  2 +-
 block/blk-sysfs.c    |  5 +----
 block/elevator.c     | 23 ++++++++---------------
 5 files changed, 11 insertions(+), 27 deletions(-)

-- 
2.25.4

[RESEND PATCH v2 1/7] block: invoke blk_mq_exit_sched no matter whether have .exit_sched

[Yufen Yu]

We will register debugfs for scheduler no matter whether it have
defined callback funciton .exit_sched. So, blk_mq_exit_sched()
is always needed to unregister debugfs. Also, q->elevator should
be set as NULL after exiting scheduler.

For now, since all register scheduler have defined .exit_sched,
it will not cause any actual problem. But It will be more reasonable
to do this change.

Signed-off-by: Yufen Yu <yuyufen@huawei.com>
---
 block/blk-sysfs.c | 1 -
 block/elevator.c  | 3 +--
 2 files changed, 1 insertion(+), 3 deletions(-)

diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index 7dda709f3ccb..ee2cd4d1054c 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -883,7 +883,6 @@ static void blk_exit_queue(struct request_queue *q)
 	if (q->elevator) {
 		ioc_clear_queue(q);
 		__elevator_exit(q, q->elevator);
-		q->elevator = NULL;
 	}
 
 	/*
diff --git a/block/elevator.c b/block/elevator.c
index 90ed7a28c21d..7d76b61e157a 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -191,8 +191,7 @@ static void elevator_release(struct kobject *kobj)
 void __elevator_exit(struct request_queue *q, struct elevator_queue *e)
 {
 	mutex_lock(&e->sysfs_lock);
-	if (e->type->ops.exit_sched)
-		blk_mq_exit_sched(q, e);
+	blk_mq_exit_sched(q, e);
 	mutex_unlock(&e->sysfs_lock);
 
 	kobject_put(&e->kobj);
-- 
2.25.4

[RESEND PATCH v2 2/7] block: remove redundant mq check

[Yufen Yu]

elv_support_iosched() will check queue_is_mq() for us. So, remove
the redundant check to clean code.

Signed-off-by: Yufen Yu <yuyufen@huawei.com>
---
 block/elevator.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/block/elevator.c b/block/elevator.c
index 7d76b61e157a..b506895b34c7 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -615,7 +615,7 @@ int elevator_switch_mq(struct request_queue *q,
 
 static inline bool elv_support_iosched(struct request_queue *q)
 {
-	if (!q->mq_ops ||
+	if (!queue_is_mq(q) ||
 	    (q->tag_set && (q->tag_set->flags & BLK_MQ_F_NO_SCHED)))
 		return false;
 	return true;
@@ -763,7 +763,7 @@ ssize_t elv_iosched_store(struct request_queue *q, const char *name,
 {
 	int ret;
 
-	if (!queue_is_mq(q) || !elv_support_iosched(q))
+	if (!elv_support_iosched(q))
 		return count;
 
 	ret = __elevator_change(q, name);
-- 
2.25.4

[RESEND PATCH v2 3/7] block: use helper function to test queue register

[Yufen Yu]

We have defined common interface blk_queue_registered() to
test QUEUE_FLAG_REGISTERED. Just use it.

Signed-off-by: Yufen Yu <yuyufen@huawei.com>
---
 block/blk-iocost.c | 2 +-
 block/elevator.c   | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/block/blk-iocost.c b/block/blk-iocost.c
index d37b55db2409..24a4dedae207 100644
--- a/block/blk-iocost.c
+++ b/block/blk-iocost.c
@@ -618,7 +618,7 @@ static struct ioc *q_to_ioc(struct request_queue *q)
 
 static const char *q_name(struct request_queue *q)
 {
-	if (test_bit(QUEUE_FLAG_REGISTERED, &q->queue_flags))
+	if (blk_queue_registered(q))
 		return kobject_name(q->kobj.parent);
 	else
 		return "<unknown>";
diff --git a/block/elevator.c b/block/elevator.c
index b506895b34c7..431a2a1c896e 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -672,7 +672,7 @@ void elevator_init_mq(struct request_queue *q)
 	if (!elv_support_iosched(q))
 		return;
 
-	WARN_ON_ONCE(test_bit(QUEUE_FLAG_REGISTERED, &q->queue_flags));
+	WARN_ON_ONCE(blk_queue_registered(q));
 
 	if (unlikely(q->elevator))
 		return;
-- 
2.25.4

[RESEND PATCH v2 4/7] blk-mq: use helper function to test hw stopped

[Yufen Yu]

We have introduced helper function blk_mq_hctx_stopped() to test
BLK_MQ_S_STOPPED.

Signed-off-by: Yufen Yu <yuyufen@huawei.com>
---
 block/blk-mq.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 47e4d5ce6196..d96292e36a23 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1783,7 +1783,7 @@ static void blk_mq_run_work_fn(struct work_struct *work)
 	/*
 	 * If we are stopped, don't run the queue.
 	 */
-	if (test_bit(BLK_MQ_S_STOPPED, &hctx->state))
+	if (blk_mq_hctx_stopped(hctx))
 		return;
 
 	__blk_mq_run_hw_queue(hctx);
-- 
2.25.4

[RESEND PATCH v2 5/7] block: fix comment and add lockdep assert

[Yufen Yu]

After commit b89f625e28d4 ("block: don't release queue's sysfs
lock during switching elevator"), whole elevator register and
unregister function are covered by sysfs_lock. So, remove wrong
comment and add lockdep assert.

Signed-off-by: Yufen Yu <yuyufen@huawei.com>
---
 block/elevator.c | 14 ++++----------
 1 file changed, 4 insertions(+), 10 deletions(-)

diff --git a/block/elevator.c b/block/elevator.c
index 431a2a1c896e..293c5c81397a 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -479,16 +479,13 @@ static struct kobj_type elv_ktype = {
 	.release	= elevator_release,
 };
 
-/*
- * elv_register_queue is called from either blk_register_queue or
- * elevator_switch, elevator switch is prevented from being happen
- * in the two paths, so it is safe to not hold q->sysfs_lock.
- */
 int elv_register_queue(struct request_queue *q, bool uevent)
 {
 	struct elevator_queue *e = q->elevator;
 	int error;
 
+	lockdep_assert_held(&q->sysfs_lock);
+
 	error = kobject_add(&e->kobj, &q->kobj, "%s", "iosched");
 	if (!error) {
 		struct elv_fs_entry *attr = e->type->elevator_attrs;
@@ -507,13 +504,10 @@ int elv_register_queue(struct request_queue *q, bool uevent)
 	return error;
 }
 
-/*
- * elv_unregister_queue is called from either blk_unregister_queue or
- * elevator_switch, elevator switch is prevented from being happen
- * in the two paths, so it is safe to not hold q->sysfs_lock.
- */
 void elv_unregister_queue(struct request_queue *q)
 {
+	lockdep_assert_held(&q->sysfs_lock);
+
 	if (q) {
 		struct elevator_queue *e = q->elevator;
 
-- 
2.25.4

[RESEND PATCH v2 6/7] block: get rid of unnecessary local variable

[Yufen Yu]

Since whole elevator register is protectd by sysfs_lock, we
don't need extras 'has_elevator'. Just use q->elevator directly.

Signed-off-by: Yufen Yu <yuyufen@huawei.com>
---
 block/blk-sysfs.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index ee2cd4d1054c..d13a70ed39bf 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -976,7 +976,6 @@ int blk_register_queue(struct gendisk *disk)
 	int ret;
 	struct device *dev = disk_to_dev(disk);
 	struct request_queue *q = disk->queue;
-	bool has_elevator = false;
 
 	if (WARN_ON(!q))
 		return -ENXIO;
@@ -1040,7 +1039,6 @@ int blk_register_queue(struct gendisk *disk)
 			kobject_put(&dev->kobj);
 			return ret;
 		}
-		has_elevator = true;
 	}
 
 	blk_queue_flag_set(QUEUE_FLAG_REGISTERED, q);
@@ -1049,7 +1047,7 @@ int blk_register_queue(struct gendisk *disk)
 
 	/* Now everything is ready and send out KOBJ_ADD uevent */
 	kobject_uevent(&q->kobj, KOBJ_ADD);
-	if (has_elevator)
+	if (q->elevator)
 		kobject_uevent(&q->elevator->kobj, KOBJ_ADD);
 	mutex_unlock(&q->sysfs_lock);
 
-- 
2.25.4

[RESEND PATCH v2 7/7] blk-mq: get rid of the dead flush handle code path

[Yufen Yu]

After commit 923218f6166a ("blk-mq: don't allocate driver tag upfront
for flush rq"), blk_mq_submit_bio() will call blk_insert_flush()
directly to handle flush request rather than blk_mq_sched_insert_request()
in the case of elevator.

Then, all flush request either have set RQF_FLUSH_SEQ flag when call
blk_mq_sched_insert_request(), or have inserted into hctx->dispatch.
So, remove the dead code path.

Signed-off-by: Yufen Yu <yuyufen@huawei.com>
---
 block/blk-mq-sched.c | 6 ------
 1 file changed, 6 deletions(-)

diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c
index d2790e5b06d1..606298fff5db 100644
--- a/block/blk-mq-sched.c
+++ b/block/blk-mq-sched.c
@@ -525,12 +525,6 @@ void blk_mq_sched_insert_request(struct request *rq, bool at_head,
 	struct blk_mq_ctx *ctx = rq->mq_ctx;
 	struct blk_mq_hw_ctx *hctx = rq->mq_hctx;
 
-	/* flush rq in flush machinery need to be dispatched directly */
-	if (!(rq->rq_flags & RQF_FLUSH_SEQ) && op_is_flush(rq->cmd_flags)) {
-		blk_insert_flush(rq);
-		goto run;
-	}
-
 	WARN_ON(e && (rq->tag != -1));
 
 	if (blk_mq_sched_bypass_insert(hctx, !!e, rq)) {
-- 
2.25.4

Re: [RESEND PATCH v2 0/7] some improvements and cleanups for block

[Jens Axboe]

On 10/8/20 9:26 PM, Yufen Yu wrote:
> Hi all,
>   This series contains improvement for elevator exit, removing
>   wrong comments and clean-up code.
> 
> Yufen Yu (7):
>   block: invoke blk_mq_exit_sched no matter whether have .exit_sched
>   block: remove redundant mq check
>   block: use helper function to test queue register
>   blk-mq: use helper function to test hw stopped
>   block: fix comment and add lockdep assert
>   block: get rid of unnecessary local variable
>   blk-mq: get rid of the dead flush handle code path
> 
>  block/blk-iocost.c   |  2 +-
>  block/blk-mq-sched.c |  6 ------
>  block/blk-mq.c       |  2 +-
>  block/blk-sysfs.c    |  5 +----
>  block/elevator.c     | 23 ++++++++---------------
>  5 files changed, 11 insertions(+), 27 deletions(-)

Applied, thanks.

-- 
Jens Axboe