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Message-Id: <1534749606-7311-2-git-send-email-jianchao.w.wang@oracle.com>
Date: Mon, 20 Aug 2018 15:20:05 +0800
From: Jianchao Wang <jianchao.w.wang@...cle.com>
To: axboe@...nel.dk
Cc: tom.leiming@...il.com, bart.vanassche@....com,
keith.busch@...ux.intel.com, linux-block@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: [PATCH V3 1/2] blk-mq: init hctx sched after update ctx and hctx mapping
Currently, when update nr_hw_queues, io scheduler's init_hctx will
be invoked before the mapping between ctx and hctx is adapted
correctly by blk_mq_map_swqueue. The io scheduler init_hctx (kyber)
may depend on this mapping and get wrong result and panic finally.
A simply way to fix this is switch the io scheduler to none before
update the nr_hw_queues, and then get it back after update nr_hw_queues.
To achieve this, we add a new member elv_type in request_queue to
save the original elevator and adapt and export elevator_switch_mq.
And also blk_mq_sched_init_/exit_hctx are removed due to nobody use
them any more.
Signed-off-by: Jianchao Wang <jianchao.w.wang@...cle.com>
Reviewed-by: Ming Lei <ming.lei@...hat.com>
---
block/blk-mq-sched.c | 44 --------------------------------------------
block/blk-mq-sched.h | 5 -----
block/blk-mq.c | 40 ++++++++++++++++++++++++++++++++--------
block/blk.h | 2 ++
block/elevator.c | 20 ++++++++++++--------
include/linux/blkdev.h | 3 +++
6 files changed, 49 insertions(+), 65 deletions(-)
diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c
index cf9c66c..29bfe80 100644
--- a/block/blk-mq-sched.c
+++ b/block/blk-mq-sched.c
@@ -462,50 +462,6 @@ static void blk_mq_sched_tags_teardown(struct request_queue *q)
blk_mq_sched_free_tags(set, hctx, i);
}
-int blk_mq_sched_init_hctx(struct request_queue *q, struct blk_mq_hw_ctx *hctx,
- unsigned int hctx_idx)
-{
- struct elevator_queue *e = q->elevator;
- int ret;
-
- if (!e)
- return 0;
-
- ret = blk_mq_sched_alloc_tags(q, hctx, hctx_idx);
- if (ret)
- return ret;
-
- if (e->type->ops.mq.init_hctx) {
- ret = e->type->ops.mq.init_hctx(hctx, hctx_idx);
- if (ret) {
- blk_mq_sched_free_tags(q->tag_set, hctx, hctx_idx);
- return ret;
- }
- }
-
- blk_mq_debugfs_register_sched_hctx(q, hctx);
-
- return 0;
-}
-
-void blk_mq_sched_exit_hctx(struct request_queue *q, struct blk_mq_hw_ctx *hctx,
- unsigned int hctx_idx)
-{
- struct elevator_queue *e = q->elevator;
-
- if (!e)
- return;
-
- blk_mq_debugfs_unregister_sched_hctx(hctx);
-
- if (e->type->ops.mq.exit_hctx && hctx->sched_data) {
- e->type->ops.mq.exit_hctx(hctx, hctx_idx);
- hctx->sched_data = NULL;
- }
-
- blk_mq_sched_free_tags(q->tag_set, hctx, hctx_idx);
-}
-
int blk_mq_init_sched(struct request_queue *q, struct elevator_type *e)
{
struct blk_mq_hw_ctx *hctx;
diff --git a/block/blk-mq-sched.h b/block/blk-mq-sched.h
index 0cb8f93..4e028ee 100644
--- a/block/blk-mq-sched.h
+++ b/block/blk-mq-sched.h
@@ -28,11 +28,6 @@ void blk_mq_sched_dispatch_requests(struct blk_mq_hw_ctx *hctx);
int blk_mq_init_sched(struct request_queue *q, struct elevator_type *e);
void blk_mq_exit_sched(struct request_queue *q, struct elevator_queue *e);
-int blk_mq_sched_init_hctx(struct request_queue *q, struct blk_mq_hw_ctx *hctx,
- unsigned int hctx_idx);
-void blk_mq_sched_exit_hctx(struct request_queue *q, struct blk_mq_hw_ctx *hctx,
- unsigned int hctx_idx);
-
static inline bool
blk_mq_sched_bio_merge(struct request_queue *q, struct bio *bio)
{
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 5efd789..7b99477 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2147,8 +2147,6 @@ static void blk_mq_exit_hctx(struct request_queue *q,
if (set->ops->exit_request)
set->ops->exit_request(set, hctx->fq->flush_rq, hctx_idx);
- blk_mq_sched_exit_hctx(q, hctx, hctx_idx);
-
if (set->ops->exit_hctx)
set->ops->exit_hctx(hctx, hctx_idx);
@@ -2216,12 +2214,9 @@ static int blk_mq_init_hctx(struct request_queue *q,
set->ops->init_hctx(hctx, set->driver_data, hctx_idx))
goto free_bitmap;
- if (blk_mq_sched_init_hctx(q, hctx, hctx_idx))
- goto exit_hctx;
-
hctx->fq = blk_alloc_flush_queue(q, hctx->numa_node, set->cmd_size);
if (!hctx->fq)
- goto sched_exit_hctx;
+ goto exit_hctx;
if (blk_mq_init_request(set, hctx->fq->flush_rq, hctx_idx, node))
goto free_fq;
@@ -2235,8 +2230,6 @@ static int blk_mq_init_hctx(struct request_queue *q,
free_fq:
kfree(hctx->fq);
- sched_exit_hctx:
- blk_mq_sched_exit_hctx(q, hctx, hctx_idx);
exit_hctx:
if (set->ops->exit_hctx)
set->ops->exit_hctx(hctx, hctx_idx);
@@ -2913,6 +2906,29 @@ static void __blk_mq_update_nr_hw_queues(struct blk_mq_tag_set *set,
list_for_each_entry(q, &set->tag_list, tag_set_list)
blk_mq_freeze_queue(q);
+ /*
+ * switch io scheduler to NULL to clean up the data in it.
+ * will get it back after update mapping between cpu and hw queues.
+ */
+ list_for_each_entry(q, &set->tag_list, tag_set_list) {
+ if (!q->elevator) {
+ q->elv_type = NULL;
+ continue;
+ }
+ q->elv_type = q->elevator->type;
+ mutex_lock(&q->sysfs_lock);
+ /*
+ * After elevator_switch_mq, the previous elevator_queue will be
+ * released by elevator_release. The reference of the io scheduler
+ * module get by elevator_get will also be put. So we need to get
+ * a reference of the io scheduler module here to prevent it to be
+ * removed.
+ */
+ __module_get(q->elv_type->elevator_owner);
+ elevator_switch_mq(q, NULL);
+ mutex_unlock(&q->sysfs_lock);
+ }
+
set->nr_hw_queues = nr_hw_queues;
blk_mq_update_queue_map(set);
list_for_each_entry(q, &set->tag_list, tag_set_list) {
@@ -2920,6 +2936,14 @@ static void __blk_mq_update_nr_hw_queues(struct blk_mq_tag_set *set,
blk_mq_queue_reinit(q);
}
+ list_for_each_entry(q, &set->tag_list, tag_set_list) {
+ if (!q->elv_type)
+ continue;
+
+ mutex_lock(&q->sysfs_lock);
+ elevator_switch_mq(q, q->elv_type);
+ mutex_unlock(&q->sysfs_lock);
+ }
list_for_each_entry(q, &set->tag_list, tag_set_list)
blk_mq_unfreeze_queue(q);
}
diff --git a/block/blk.h b/block/blk.h
index d4d67e9..0c9bc8d 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -234,6 +234,8 @@ static inline void elv_deactivate_rq(struct request_queue *q, struct request *rq
int elevator_init(struct request_queue *);
int 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 *);
int elv_register_queue(struct request_queue *q);
void elv_unregister_queue(struct request_queue *q);
diff --git a/block/elevator.c b/block/elevator.c
index fa828b5..5ea6e7d 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -933,16 +933,13 @@ void elv_unregister(struct elevator_type *e)
}
EXPORT_SYMBOL_GPL(elv_unregister);
-static int elevator_switch_mq(struct request_queue *q,
+int elevator_switch_mq(struct request_queue *q,
struct elevator_type *new_e)
{
int ret;
lockdep_assert_held(&q->sysfs_lock);
- blk_mq_freeze_queue(q);
- blk_mq_quiesce_queue(q);
-
if (q->elevator) {
if (q->elevator->registered)
elv_unregister_queue(q);
@@ -968,8 +965,6 @@ static int elevator_switch_mq(struct request_queue *q,
blk_add_trace_msg(q, "elv switch: none");
out:
- blk_mq_unquiesce_queue(q);
- blk_mq_unfreeze_queue(q);
return ret;
}
@@ -1021,8 +1016,17 @@ static int elevator_switch(struct request_queue *q, struct elevator_type *new_e)
lockdep_assert_held(&q->sysfs_lock);
- if (q->mq_ops)
- return elevator_switch_mq(q, new_e);
+ if (q->mq_ops) {
+ blk_mq_freeze_queue(q);
+ blk_mq_quiesce_queue(q);
+
+ err = elevator_switch_mq(q, new_e);
+
+ blk_mq_unquiesce_queue(q);
+ blk_mq_unfreeze_queue(q);
+
+ return err;
+ }
/*
* Turn on BYPASS and drain all requests w/ elevator private data.
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index d6869e0..ee930c4 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -437,6 +437,9 @@ struct request_queue {
struct list_head queue_head;
struct request *last_merge;
struct elevator_queue *elevator;
+
+ /* used when update nr_hw_queues */
+ struct elevator_type *elv_type;
int nr_rqs[2]; /* # allocated [a]sync rqs */
int nr_rqs_elvpriv; /* # allocated rqs w/ elvpriv */
--
2.7.4
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