From: Marcos Paulo de Souza <marcos.souza.org@gmail.com>
To: linux-kernel@vger.kernel.org
Cc: Marcos Paulo de Souza <marcos.souza.org@gmail.com>,
Jens Axboe <axboe@kernel.dk>,
linux-block@vger.kernel.org (open list:BLOCK LAYER)
Subject: [PATCH] block: elevator.c: Check elevator kernel argument again
Date: Sat, 13 Jul 2019 00:52:21 -0300 [thread overview]
Message-ID: <20190713035221.31508-1-marcos.souza.org@gmail.com> (raw)
Since the inclusion of blk-mq, elevator= kernel argument was not being
considered anymore, making it impossible to specify a specific elevator
at boot time as it was used before.
This is done by checking chosen_elevator global variable, which is
populated once elevator= kernel argument is passed. Without this patch,
mq-deadline is the only elevator that is can be used at boot time.
Signed-off-by: Marcos Paulo de Souza <marcos.souza.org@gmail.com>
---
I found this issue while inspecting why noop scheduler was gone, and so I found
that was now impossible to use a scheduler different from mq-deadeline.
Am I missing something? Is this a desirable behavior?
One more question: currently we can't specify a "none" scheduler, like it used
to be "noop". This is also on purpose? If it's not, I can provide a patch for
it.
block/elevator.c | 17 +++++++++++++----
1 file changed, 13 insertions(+), 4 deletions(-)
diff --git a/block/elevator.c b/block/elevator.c
index 2f17d66d0e61..41ce7ba099ba 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -601,7 +601,7 @@ int elevator_switch_mq(struct request_queue *q,
*/
int elevator_init_mq(struct request_queue *q)
{
- struct elevator_type *e;
+ struct elevator_type *e = NULL;
int err = 0;
if (q->nr_hw_queues != 1)
@@ -615,9 +615,18 @@ int elevator_init_mq(struct request_queue *q)
if (unlikely(q->elevator))
goto out_unlock;
- e = elevator_get(q, "mq-deadline", false);
- if (!e)
- goto out_unlock;
+ /* if elevator was used as kernel argument, try to load it */
+ if (*chosen_elevator) {
+ e = elevator_get(q, chosen_elevator, false);
+ if (!e)
+ pr_err("io scheduler %s not found", chosen_elevator);
+ }
+
+ if (!e) {
+ e = elevator_get(q, "mq-deadline", false);
+ if (!e)
+ goto out_unlock;
+ }
err = blk_mq_init_sched(q, e);
if (err)
--
2.22.0
next reply other threads:[~2019-07-13 3:51 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-13 3:52 Marcos Paulo de Souza [this message]
2019-07-13 21:53 ` [PATCH] block: elevator.c: Check elevator kernel argument again Jens Axboe
2019-07-14 4:01 ` Marcos Paulo de Souza
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