From: Damien Le Moal <damien.lemoal@wdc.com>
Date: Thu, 5 Sep 2019 18:51:30 +0900
Subject: [PATCH] block: Change elevator_init_mq() to always succeed
References: bsc#1156419,jsc#SLE-8281
Git-commit: 954b4a5ce4a806e7c284ce6b2659abdd03d0b6e2
Patch-mainline: v5.4-rc1
If the default elevator chosen is mq-deadline, elevator_init_mq() may
return an error if mq-deadline initialization fails, leading to
blk_mq_init_allocated_queue() returning an error, which in turn will
cause the block device initialization to fail and the device not being
exposed.
Instead of taking such extreme measure, handle mq-deadline
initialization failures in the same manner as when mq-deadline is not
available (no module to load), that is, default to the "none" scheduler.
With this change, elevator_init_mq() return type can be changed to void.
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Hannes Reinecke <hare@suse.de>
---
block/blk-mq.c | 8 +-------
block/blk.h | 2 +-
block/elevator.c | 23 ++++++++++++-----------
3 files changed, 14 insertions(+), 19 deletions(-)
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 029bbfcefeba..5673d7f52746 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2852,8 +2852,6 @@ static unsigned int nr_hw_queues(struct blk_mq_tag_set *set)
struct request_queue *blk_mq_init_allocated_queue(struct blk_mq_tag_set *set,
struct request_queue *q)
{
- int ret = -ENOMEM;
-
/* mark the queue as mq asap */
q->mq_ops = set->ops;
@@ -2914,14 +2912,10 @@ struct request_queue *blk_mq_init_allocated_queue(struct blk_mq_tag_set *set,
blk_mq_add_queue_tag_set(set, q);
blk_mq_map_swqueue(q);
- ret = elevator_init_mq(q);
- if (ret)
- goto err_tag_set;
+ elevator_init_mq(q);
return q;
-err_tag_set:
- blk_mq_del_queue_tag_set(q);
err_hctxs:
kfree(q->queue_hw_ctx);
q->nr_hw_queues = 0;
diff --git a/block/blk.h b/block/blk.h
index 0c6076f45598..47fba9362e60 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -191,7 +191,7 @@ void blk_account_io_done(struct request *req, u64 now);
void blk_insert_flush(struct request *rq);
-int elevator_init_mq(struct request_queue *q);
+void elevator_init_mq(struct request_queue *q);
int elevator_switch_mq(struct request_queue *q,
struct elevator_type *new_e);
void __elevator_exit(struct request_queue *, struct elevator_queue *);
diff --git a/block/elevator.c b/block/elevator.c
index 4721834815bb..2944c129760c 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -628,34 +628,35 @@ static inline bool elv_support_iosched(struct request_queue *q)
/*
* For blk-mq devices supporting IO scheduling, we default to using mq-deadline,
- * if available, for single queue devices. If deadline isn't available OR we
- * have multiple queues, default to "none".
+ * if available, for single queue devices. If deadline isn't available OR
+ * deadline initialization fails OR we have multiple queues, default to "none".
*/
-int elevator_init_mq(struct request_queue *q)
+void elevator_init_mq(struct request_queue *q)
{
struct elevator_type *e;
- int err = 0;
+ int err;
if (!elv_support_iosched(q))
- return 0;
+ return;
if (q->nr_hw_queues != 1)
- return 0;
+ return;
WARN_ON_ONCE(test_bit(QUEUE_FLAG_REGISTERED, &q->queue_flags));
if (unlikely(q->elevator))
- goto out;
+ return;
e = elevator_get(q, "mq-deadline", false);
if (!e)
- goto out;
+ return;
err = blk_mq_init_sched(q, e);
- if (err)
+ if (err) {
+ pr_warn("\"%s\" elevator initialization failed, "
+ "falling back to \"none\"\n", e->elevator_name);
elevator_put(e);
-out:
- return err;
+ }
}
--
2.16.4