From: Nilay Shroff <nilay@linux.ibm.com>
To: linux-block@vger.kernel.org
Cc: ming.lei@redhat.com, hch@lst.de, axboe@kernel.dk,
yi.zhang@redhat.com, czhong@redhat.com, yukuai@fnnas.com,
gjoyce@ibm.com
Subject: [PATCHv7 4/5] block: use {alloc|free}_sched data methods
Date: Thu, 13 Nov 2025 14:28:21 +0530 [thread overview]
Message-ID: <20251113090619.2030737-5-nilay@linux.ibm.com> (raw)
In-Reply-To: <20251113090619.2030737-1-nilay@linux.ibm.com>
The previous patch introduced ->alloc_sched_data and
->free_sched_data methods. This patch builds upon that
by now using these methods during elevator switch and
nr_hw_queue update.
It's also ensured that scheduler-specific data is
allocated and freed through the new callbacks outside
of the ->freeze_lock and ->elevator_lock locking contexts,
thereby preventing any dependency on pcpu_alloc_mutex.
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Yu Kuai <yukuai@fnnas.com>
Signed-off-by: Nilay Shroff <nilay@linux.ibm.com>
---
block/blk-mq-sched.c | 27 +++++++++++++++++++++------
block/blk-mq-sched.h | 5 ++++-
block/elevator.c | 34 ++++++++++++++++++++++------------
block/elevator.h | 4 +++-
4 files changed, 50 insertions(+), 20 deletions(-)
diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c
index 03ff16c49976..128f2be9d420 100644
--- a/block/blk-mq-sched.c
+++ b/block/blk-mq-sched.c
@@ -428,12 +428,17 @@ void blk_mq_free_sched_tags(struct elevator_tags *et,
}
void blk_mq_free_sched_res(struct elevator_resources *res,
+ struct elevator_type *type,
struct blk_mq_tag_set *set)
{
if (res->et) {
blk_mq_free_sched_tags(res->et, set);
res->et = NULL;
}
+ if (res->data) {
+ blk_mq_free_sched_data(type, res->data);
+ res->data = NULL;
+ }
}
void blk_mq_free_sched_res_batch(struct xarray *elv_tbl,
@@ -458,7 +463,7 @@ void blk_mq_free_sched_res_batch(struct xarray *elv_tbl,
WARN_ON_ONCE(1);
continue;
}
- blk_mq_free_sched_res(&ctx->res, set);
+ blk_mq_free_sched_res(&ctx->res, ctx->type, set);
}
}
}
@@ -541,7 +546,9 @@ struct elevator_tags *blk_mq_alloc_sched_tags(struct blk_mq_tag_set *set,
}
int blk_mq_alloc_sched_res(struct request_queue *q,
- struct elevator_resources *res, unsigned int nr_hw_queues)
+ struct elevator_type *type,
+ struct elevator_resources *res,
+ unsigned int nr_hw_queues)
{
struct blk_mq_tag_set *set = q->tag_set;
@@ -550,6 +557,12 @@ int blk_mq_alloc_sched_res(struct request_queue *q,
if (!res->et)
return -ENOMEM;
+ res->data = blk_mq_alloc_sched_data(q, type);
+ if (IS_ERR(res->data)) {
+ blk_mq_free_sched_tags(res->et, set);
+ return -ENOMEM;
+ }
+
return 0;
}
@@ -577,19 +590,21 @@ int blk_mq_alloc_sched_res_batch(struct xarray *elv_tbl,
goto out_unwind;
}
- ret = blk_mq_alloc_sched_res(q, &ctx->res,
- nr_hw_queues);
+ ret = blk_mq_alloc_sched_res(q, q->elevator->type,
+ &ctx->res, nr_hw_queues);
if (ret)
goto out_unwind;
}
}
return 0;
+
out_unwind:
list_for_each_entry_continue_reverse(q, &set->tag_list, tag_set_list) {
if (q->elevator) {
ctx = xa_load(elv_tbl, q->id);
if (ctx)
- blk_mq_free_sched_res(&ctx->res, set);
+ blk_mq_free_sched_res(&ctx->res,
+ ctx->type, set);
}
}
return ret;
@@ -606,7 +621,7 @@ int blk_mq_init_sched(struct request_queue *q, struct elevator_type *e,
unsigned long i;
int ret;
- eq = elevator_alloc(q, e, et);
+ eq = elevator_alloc(q, e, res);
if (!eq)
return -ENOMEM;
diff --git a/block/blk-mq-sched.h b/block/blk-mq-sched.h
index 4e1b86e85a8a..02c40a72e959 100644
--- a/block/blk-mq-sched.h
+++ b/block/blk-mq-sched.h
@@ -26,7 +26,9 @@ void blk_mq_sched_free_rqs(struct request_queue *q);
struct elevator_tags *blk_mq_alloc_sched_tags(struct blk_mq_tag_set *set,
unsigned int nr_hw_queues, unsigned int nr_requests);
int blk_mq_alloc_sched_res(struct request_queue *q,
- struct elevator_resources *res, unsigned int nr_hw_queues);
+ struct elevator_type *type,
+ struct elevator_resources *res,
+ unsigned int nr_hw_queues);
int blk_mq_alloc_sched_res_batch(struct xarray *elv_tbl,
struct blk_mq_tag_set *set, unsigned int nr_hw_queues);
int blk_mq_alloc_sched_ctx_batch(struct xarray *elv_tbl,
@@ -35,6 +37,7 @@ void blk_mq_free_sched_ctx_batch(struct xarray *elv_tbl);
void blk_mq_free_sched_tags(struct elevator_tags *et,
struct blk_mq_tag_set *set);
void blk_mq_free_sched_res(struct elevator_resources *res,
+ struct elevator_type *type,
struct blk_mq_tag_set *set);
void blk_mq_free_sched_res_batch(struct xarray *et_table,
struct blk_mq_tag_set *set);
diff --git a/block/elevator.c b/block/elevator.c
index cbec292a4af5..5b37ef44f52d 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -121,7 +121,7 @@ static struct elevator_type *elevator_find_get(const char *name)
static const struct kobj_type elv_ktype;
struct elevator_queue *elevator_alloc(struct request_queue *q,
- struct elevator_type *e, struct elevator_tags *et)
+ struct elevator_type *e, struct elevator_resources *res)
{
struct elevator_queue *eq;
@@ -134,7 +134,8 @@ struct elevator_queue *elevator_alloc(struct request_queue *q,
kobject_init(&eq->kobj, &elv_ktype);
mutex_init(&eq->sysfs_lock);
hash_init(eq->hash);
- eq->et = et;
+ eq->et = res->et;
+ eq->elevator_data = res->data;
return eq;
}
@@ -617,7 +618,7 @@ static void elv_exit_and_release(struct elv_change_ctx *ctx,
mutex_unlock(&q->elevator_lock);
blk_mq_unfreeze_queue(q, memflags);
if (e) {
- blk_mq_free_sched_res(&ctx->res, q->tag_set);
+ blk_mq_free_sched_res(&ctx->res, ctx->type, q->tag_set);
kobject_put(&e->kobj);
}
}
@@ -628,12 +629,15 @@ static int elevator_change_done(struct request_queue *q,
int ret = 0;
if (ctx->old) {
- struct elevator_resources res = {.et = ctx->old->et};
+ struct elevator_resources res = {
+ .et = ctx->old->et,
+ .data = ctx->old->elevator_data
+ };
bool enable_wbt = test_bit(ELEVATOR_FLAG_ENABLE_WBT_ON_EXIT,
&ctx->old->flags);
elv_unregister_queue(q, ctx->old);
- blk_mq_free_sched_res(&res, q->tag_set);
+ blk_mq_free_sched_res(&res, ctx->old->type, q->tag_set);
kobject_put(&ctx->old->kobj);
if (enable_wbt)
wbt_enable_default(q->disk);
@@ -658,7 +662,8 @@ static int elevator_change(struct request_queue *q, struct elv_change_ctx *ctx)
lockdep_assert_held(&set->update_nr_hwq_lock);
if (strncmp(ctx->name, "none", 4)) {
- ret = blk_mq_alloc_sched_res(q, &ctx->res, set->nr_hw_queues);
+ ret = blk_mq_alloc_sched_res(q, ctx->type, &ctx->res,
+ set->nr_hw_queues);
if (ret)
return ret;
}
@@ -681,11 +686,12 @@ static int elevator_change(struct request_queue *q, struct elv_change_ctx *ctx)
blk_mq_unfreeze_queue(q, memflags);
if (!ret)
ret = elevator_change_done(q, ctx);
+
/*
* Free sched resource if it's allocated but we couldn't switch elevator.
*/
if (!ctx->new)
- blk_mq_free_sched_res(&ctx->res, set);
+ blk_mq_free_sched_res(&ctx->res, ctx->type, set);
return ret;
}
@@ -711,11 +717,12 @@ void elv_update_nr_hw_queues(struct request_queue *q,
blk_mq_unfreeze_queue_nomemrestore(q);
if (!ret)
WARN_ON_ONCE(elevator_change_done(q, ctx));
+
/*
* Free sched resource if it's allocated but we couldn't switch elevator.
*/
if (!ctx->new)
- blk_mq_free_sched_res(&ctx->res, set);
+ blk_mq_free_sched_res(&ctx->res, ctx->type, set);
}
/*
@@ -729,7 +736,6 @@ void elevator_set_default(struct request_queue *q)
.no_uevent = true,
};
int err;
- struct elevator_type *e;
/* now we allow to switch elevator */
blk_queue_flag_clear(QUEUE_FLAG_NO_ELV_SWITCH, q);
@@ -742,8 +748,8 @@ void elevator_set_default(struct request_queue *q)
* have multiple queues or mq-deadline is not available, default
* to "none".
*/
- e = elevator_find_get(ctx.name);
- if (!e)
+ ctx.type = elevator_find_get(ctx.name);
+ if (!ctx.type)
return;
if ((q->nr_hw_queues == 1 ||
@@ -753,7 +759,7 @@ void elevator_set_default(struct request_queue *q)
pr_warn("\"%s\" elevator initialization, failed %d, falling back to \"none\"\n",
ctx.name, err);
}
- elevator_put(e);
+ elevator_put(ctx.type);
}
void elevator_set_none(struct request_queue *q)
@@ -802,6 +808,7 @@ ssize_t elv_iosched_store(struct gendisk *disk, const char *buf,
ctx.name = strstrip(elevator_name);
elv_iosched_load_module(ctx.name);
+ ctx.type = elevator_find_get(ctx.name);
down_read(&set->update_nr_hwq_lock);
if (!blk_queue_no_elv_switch(q)) {
@@ -812,6 +819,9 @@ ssize_t elv_iosched_store(struct gendisk *disk, const char *buf,
ret = -ENOENT;
}
up_read(&set->update_nr_hwq_lock);
+
+ if (ctx.type)
+ elevator_put(ctx.type);
return ret;
}
diff --git a/block/elevator.h b/block/elevator.h
index e34043f6da26..3ee1d494f48a 100644
--- a/block/elevator.h
+++ b/block/elevator.h
@@ -33,6 +33,8 @@ struct elevator_tags {
};
struct elevator_resources {
+ /* holds elevator data */
+ void *data;
/* holds elevator tags */
struct elevator_tags *et;
};
@@ -185,7 +187,7 @@ ssize_t elv_iosched_store(struct gendisk *disk, const char *page, size_t count);
extern bool elv_bio_merge_ok(struct request *, struct bio *);
struct elevator_queue *elevator_alloc(struct request_queue *,
- struct elevator_type *, struct elevator_tags *);
+ struct elevator_type *, struct elevator_resources *);
/*
* Helper functions.
--
2.51.0
next prev parent reply other threads:[~2025-11-13 9:06 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-11-13 8:58 [PATCHv7 0/5] block: restructure elevator switch path and fix a lockdep splat Nilay Shroff
2025-11-13 8:58 ` [PATCHv7 1/5] block: unify elevator tags and type xarrays into struct elv_change_ctx Nilay Shroff
2025-11-13 8:58 ` [PATCHv7 2/5] block: move elevator tags into struct elevator_resources Nilay Shroff
2025-11-13 8:58 ` [PATCHv7 3/5] block: introduce alloc_sched_data and free_sched_data elevator methods Nilay Shroff
2025-11-13 9:57 ` Ming Lei
2025-11-13 8:58 ` Nilay Shroff [this message]
2025-11-13 8:58 ` [PATCHv7 5/5] block: define alloc_sched_data and free_sched_data methods for kyber Nilay Shroff
2025-11-13 16:39 ` [PATCHv7 0/5] block: restructure elevator switch path and fix a lockdep splat Jens Axboe
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